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419 Cards in this Set
- Front
- Back
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What are the characteristics of bacterial chromosomes?
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Circular
-Borellia spp linear Organized into ~ 50 domains ~1 mm long (500x length of the bacterium) Domains are supercoiled (implications for gene expression, esp. virulence genes) |
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Plasmids
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Extrachromosomal genetic elements
Capable of autonomous replication |
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lysogenic conversion
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refers to when a nonvirulent strain of bacteria acquires a prophage encoding a virulence factor and therby converts to a virulent strain
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What is the defining factor about transposons?
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cannot replicate autonomously-Must be integrated into a replicating molecule (chromosome, plasmid or virus) to be maintained
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IS element transposon
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major cause of bacterial mutation
inactivate genes catalyze DNA rearrangments(deletions, inversions, and replicon fusion) |
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What is necessary for a stable genetic exchange?
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integration of the DNA fragment into the bacterial chromosome or plasmid via recombination
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Transformation
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Uptake of DNA from the environment!!!
DNA bound by specific receptors and transported into the cytoplasm, one strand being degraded (Haemophilus, Bacillus) May require specific DNA recognition sequences (Neisseria) |
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Conjugation
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Transfer of DNA from donor to recipient requiring cell-cell contact!!!
Usually involves participation of a conjugal plasmid |
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Conjugal plasmids
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Carry a set of genes necessary for conjugal transfer of DNA
Transfer begins at a specific site on the plasmid, the origin of transfer, and proceeds by rolling circle replication |
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Forming mating pairs in Gram NEGATIVE(Ecoli)
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Sex pilus contacts recipient
Pilus retracts bringing donor and recipient into close contact Formation of mating pore allowing transfer of DNA |
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Forming mating pairs in Gram Positive(E.faecalis)
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Recipient secretes peptide pheromone to attract donors
Mating aggregates form |
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Hfr transfer
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Conjugal plasmid integrates into chromosome
Transfer begins within integrated plasmid Chromosomal DNA transferred to recipient |
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F prime plasmid formation
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Occasionally an integrated plasmid excises carrying a fragment of chromosomal DNA
This F’ plasmid can transfer to recipient cells The chromosomal fragment is maintained as part of the plasmid No recombination with the recipient chromosome is required |
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Transduction
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Packaging of bacterial DNA into a viral particle
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Conjugative transposons
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Move from one site in the DNA to another – transposition
Move from donor to recipient during transposition – conjugation |
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What is diauxic growth?
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ability of bacteria to preferentially use feul in an enviornment of multiple feuls
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How does inducer exclusion work?
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when glucose enters cell it is phosphorylate leaving a lot of IIeGLU that inhibits lactose permease
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What happens in the absence of glucose?
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Phosphorylated IIeP activates adenylate cyclase which produces cAMP which activate the lac operon via CAP
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Describe global regulation of CAP
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CAP works on many operons when activated but specific signals causes requisite catabolic genes.
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Nitrogen uptake
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glutamine synthetase converts NH3 and glutamate into glutamine in an ATP dependent reaction
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How is glutamine synthetase transcription activated?
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When there is a high ration of a-ketoglutarate/glutamine ration, NtrC is phosphorylated and activates transcription via sigma54
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heat shock
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sigma 32 activates genes which either refold of degrade unfolded proteins
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how do bacteria monitor its population and environment?
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through a general signal AI-2 and a species specific signal AI-1.
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single stranded DNA virus
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parvovirus
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double stranded DNA virus
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poxvirus
herpesvirus adenovirus papovirus hepadnavirus |
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RNA + virus
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picornavirus
togavirus flavivirus coronavirus claicivirus |
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RNA - virus
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orthamyxovirus
paramyxovirus arenavirus rhabdovirus bunyavirus |
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Double stranded RNA virus
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Reovirus
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Course of disease
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Acute-common cold
Late complications-measles-SSPE Latent-varicello-zoster Chronic-hep B Chronic/late-HIV Slow-prion |
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Parvovirus examples
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B19
AAV |
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Papovirus examples
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polyoma-BK,JC
papilloma-HPV1 |
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Herpesvirus examples
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HSV
VZV CMV EBV HHV6,7 Kaposi |
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Poxvirus examples
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vaccinia
variola |
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What are the features of virus used in classification
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virus genome structure
presence/absence of envelope |
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Which viruses are enveloped?
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DNA-pox, herpes, hepadna
RNA-all |
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Which viruses are not enveloped?
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DNA-parvo, papova (polyoma, papilloma), adeno
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Characteristics of parvoviridiae
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-replicate autonomously
-require cell to enter S phase of cell cycle for virus replication -Only single strand DNA virus with + or - strand polarity -B19 is the known only disease causing infectious family member in humans |
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B19 replication
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-repilicates in RBC precursor
-genome has hairpin that act as primers for DNAP -duplicated and transcribed in nucleus -CAP and genome form caspid which is released upon lysis |
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Pathogenesis of B19
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-mainly erythema infectiosum (“slapped cheek”, “fifth disease”)
-associated with arthritis -Primary infection in 2nd trimester may manifest as fetal hydrops – severe fetal anemia causing cardiac failure with associated edema |
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What patients can B19 cause aplastic crisis and chronic anemia?
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aplastic-sickle cell, thalassemia
Chronic-immunodeficient patients |
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What is the treatment for B19 induced fetal hydrops?
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watchful waiting
high dose IG intrauterine fetal transfusion *no prophylaxis available |
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Polyomavirus
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-polyomaviruses are able to manipulate host cell cycle to facilitate virus replication
-encode large T antigen, that is able through inactivation of pRB and p53. |
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T antigen
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-helicase activity
-inactivates tumor suppressors -tricks cells into entering S phase to aid viral replication |
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Human Polyoma Virus
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-BK, JC
Transmission -respiratory Epidemiology -aquired during childhood Pathogenesis-reactivated or primary infection during renal transplants can cause severe infection |
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Progressive multifocal leukoencephalopathy (PML)
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Demyelinating disease, associated with 2-4% of AIDS patients
caused by polyoma virus |
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HPV
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Transmission - direct contact
Primary infection - infects basal layer of epithelial cells Latency - remains in basal epithelium Reactivation - normally causes warts(virus forces warts to divide--tumor possible) |
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Tumor transformation in HPV
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-viral genome disrupts E2 upon insertion which control E7-pRB binding
-E7-pRB binding helps release control of cell cycle |
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Common Wart
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Members: HPV 1,2,4
Transmission: direct contact Penetration: break in dead cell layer Organ affected: skin Clinical significance: common and superficial |
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Flat (planar) Warts
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Members: HPV 1,3,4,9,10
Transmission: direct contact Penetration: break in dead cell layer Organ affected: skin - usually hands and feet Clinical significance: nuisance and difficult to remove |
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Laryngeal HPV
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HPV11
Transmission: during birth Penetration: none required Organ affected: exposed epithelial cells of larynx Clinical significance: grow rapidly, may affect speech, can be life threatening if airway becomes blocked |
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Epidermodysplasia Verruciformis
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rare disease that is thought to involve an underlying dysfunction in cell mediated immunity (autosomal recessive)
-Eruptive, polymorphic, warty papules and plaques |
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Gentital Warts
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Members: HPV 6,11,16,18
Transmission: sexual Penetration: break in dead cell layer Organ affected: skin - genital area Clinical significance: nuisance with occasional malignant conversion (HPV16,18) |
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What percentage of cervical cancer is associated with HPV?
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85%
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HPV Tumor associations
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5,8-skin carcinomas in EV pts
16,18,31,33-genital tract cancer 6,11-malignant prog. of respiratory carcinomas |
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Adenovirus replication
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drives infected cell's cycle via E1A which binds to inactivate pRB and E1B which binds to inactivate p53
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What is important about adenovirus' complicated replication?
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many levels to target therapies
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Adenoviruses
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Transmission - aerosol, close contact, possibly oral-fecal
Primary infection- epithelial cells of mucous membranes of respiratory tract, gastrointestinal tract, or cornea/conjuctiva Persistent (latent?) infection in lymphoid tissues (tonsils, adenoids) |
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epidemic keratoconjunctivitis (shipyard eye)--adenovirus
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Virus serotypes: Ad8
Symptoms: tearing, inflammation, corneal infiltrates (can cause lasting visual impairment) medical instruments |
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conjunctivitis, pharyngo-conjunctival fever--adenovirus
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serotypes: Ad3, Ad7
Symptoms: mild pharyngitis, sore throat, mild inflammation of conjunctiva Inadequate chlorination of swimming pools |
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infant respiratory disease--adenovirus
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serotypes: Ad1, Ad2, Ad5, Ad6
Symptoms: fever, aches, sore throat, cough Treatment: none |
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acute respiratory disease (ARD)--adenovirus
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serotypes: Ad4 and Ad7
Symptoms: headaches, cough, pharyngitis, fever Treatment: oral live virus vaccine Only available to the military |
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Waht are the three classes of herpes virus?
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Alpha-herpesviruses (neurotropic)
Beta-herpesviruses Gamma-herpesviruses (lymphotropic) |
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Alpha-herpesviruses
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HSV 1
HSV 2 VZV simian |
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Beta-herpesviruses
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CMV
HHV6 HHV7 |
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Gamma-herpesviruses
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EBV
KSHV (HHV8) |
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How long do herpesvirus infect their host?
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LIFE
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Herpesvirus latency
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-limited viral gene expression
-Viral genome exists as an episome in the nucleus of infected cell -upon stimulation virus undergoes reactivation |
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Distinctive characteristics of alpha herpes
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-acute disease of epithelial tissues
-latency in sensory ganglia -recurrent infections of epithelial tissues result in lesions |
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HSV-1
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-high prevalence
-transmitted by close contact -causes mild epithelial lesions -can cause encepalitis, neonatal herpes -leading cause of blindness in US |
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HSV-1 primary infection
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-Usually cold sores
Sore throat, fever, and -encephalitis (rare) are also seen -Less frequently found as a genital infection |
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HSV-1 Latent infection
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-Asymptomatic – little or no virus or virion proteins produced
-Viral DNA resides in sensory neurons of (usually) trigeminal ganglion |
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HSV-1 Recurrent infection
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Virus replicates and travels down sensory nerve fiber to infect epithelial cells around the nose and mouth
Symptoms are usually a milder form of primary infection |
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HSV-2
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-typically transmitted by sex
-usually causes relatively mild epithelial lesions -can cause encephalitis -major cause of neonatal herpes |
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HSV-2 primary infection
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Usually vesicular eruptions on the genetalia
Spread by sexual contact Affects both sexes Less frequently found as herpes labialis (cold sores) |
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HSV-2 Latent infection
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Little or no virus or virion proteins produced
Viral DNA resides in sensory neurons of (usually) sacral ganglia |
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HSV-2 Recurrent infection
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Milder outbreak, usually in same location in genital area
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Varicella Zoster virus (VZV)
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Transmission is by close contact with vesicle fluid, and probably by an aerosol/respiratory route
primary-chicken pox recurrent-shingles |
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Varicella Zoster primary infection
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Infection occurs in seasonal epidemics as chicken pox (Varicella)
Contracted from another infected individual, usually a child Systemic infection resulting in a generalized, vesicular rash |
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Varicella Zoster Latent infection
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Asymptomatic with no virus or virion proteins produced
Viral DNA resides in cells of sensory ganglia |
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Varicella Zoster Recurrent infection
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Virus travels down sensory nerve fibers and infects epithelial cells enervated by the fiber
Infections are unilateral, painful vesicular eruptions localized to the dermatome, usually in the head or upper trunk Severe systemic infections are observed in immunocompromised individuals |
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Herpes B virus
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Herpes simplex of old world monkeys
Transmitted by bites; seen in animal handlers 80% fatality rate, causes encephalitis |
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Distinctive characteristics of beta herpesvirus
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-Primary infection is usually asymptomatic
-Latency in lymphoid tissues ? -Recurrent infection is usually asymptomatic (?) -CMV can cross placenta and cause congenital birth defects |
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CMV
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Infection ages 0-5 or >18
US seroprevalence 50%, worldwide >90% Transmission by contact with virus in secretions, particularly breast milk |
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CMV pathogenesis
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-when infected by breast milk, asymptomatic
-can be transmitted transplacentally during primary or recurrent infection of mother -leading infectious cause of congenital birth defects in US -primary infection of adults can cause infectious mononucleosis (EBV is most common cause of IM) -AIDS: disseminated infections, including pneumonia, gastroenteritis, encephalitis, and retinitis |
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CMV primary, latent, and recurrent infection
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Primary infection: epithelial tissues of oral mucosa, possibly STD
Latency: site unknown, probably macrophages Recurrent infection: virus shed from saliva, urine, vaginal secretions, semen, breast milk, and feces |
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HHV6
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-Infection-children 0-2 years
-seroprevalence >70% -primary infection causes exanthem subitum (roseola) -site of latency unknown; reactivation not associated with any known disease -recent association with non-HSV viral encephalitis |
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HHV7
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Infection 2-10 years
US seroprevalence >70% Pathogenesis-recent association with non-HHV6 rash in children |
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Distinctive characteristics of gamma herpes virus
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Latent infection of B cells + other cell types??
-EBV: infectious mononucleosis -KSHV: ??? Recurrent disease asymptomatic Associated with several cancers |
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EBV
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Infection-early childhood or late teens/early 20s
seroprevalence 70% Transmission-contact of oral mucosa with saliva containing virus |
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EBV Pathogenesis
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primary infection usually asymptomatic in children; causes infectious mononucleosis in ~50% of adults
associated with several cancers in immunocompetent hosts major problem in transplant patients, cause of malignant B cell lymphomas AIDS: oral hairy leukoplakia |
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EBV primary, latent, and recurrent infections
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-Primary infection in epithelial cells of oral mucosa, followed by infection of B lymphocytes?
-Latency in B lymphocytes -Reactivation results in virus shedding in saliva |
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EBV associated tumors
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Endemic Burkitt’s lymphoma (100%)
Nasopharyngeal carcinoma (100%) Hodgkin’s lymphoma (30-50%) Lymphoma in immunosuppressed patients (~50%) Breast cancer ??? |
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KSHV (HHV-8)
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gamma Herpesvirus, found in Kaposi’s sarcoma of AIDS and non-AIDs patients
tightly associated with a rare B cell lymphoma, peritoneal effusion lymphoma (PEL), that occurs in AIDS patients |
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POXVIRUSES
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-Largest and most complex viruses known
-Oval or “brick-shaped” particles 200-400 nm in length -Extracellular virus contains 2 membranes (EEV – extracellular enveloped virions) -Intracellular particles only have an inner membrane (IMV – intracellular mature virions) |
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Poxvirus replication
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-poxviruses replicate in the cytoplasm(unique for DNA virus
-Encodes all the necessary replication and transcription enzymes to autonomously replicate -early and late gene expression |
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human infections of the poxvirus
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Vaccinia
Cowpox Molluscum contagiosum-warty papule Monkey pox |
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Small pox (variola virus)
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Epidemiology: last natural case of smallpox was diagnosed in 1977
Source: only from close contact with infected persons No animal reservoir or vector No latency in humans Spread: via droplet infection of pharyngeal secretions (ulcers in pharynx) Incubation: 10-12 days |
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Major illness caused by small pox
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rather similar to severe chicken pox
Abrubt onset of fever and prostration with macular rash on the third day Progresses to vesicles which become pustular, ulcerated, scabbed, healed with scarring (“pock marked”) 16-30% mortality |
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what are the two varieties of small pox?
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Variola minor 1% mortality
Variola major 5- 30% mortality |
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Small pox vs. chicken pox
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fever 3 days before rash, slow development, centrifugal distribution, common on palms and soles
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What is severe small pox like?
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In severe disease patients became very toxemic and
dehydrated - massive inflammatory response (cytokine release) - capillary leak -> intravascular depletion -hypotension -multisystem organ failure |
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Picornaviridae
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enteroviruses
rhinovirus cardiovirus hepatovirus aphthovirus parechovirus |
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which has the most serotypes and what does this mean?
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rhinoviruses have so many serotypes that it is hard to create a vaccine for it
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what are the different types of enteroviruses?
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poliovirus
coxsackievirus echovirus enterovirus |
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ENTEROVIRUSES
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Host range-Human viruses, no natural reserviors
Epidemiology-Worldwide distribution -Asymptomatic infection common -Primarily fecal-oral route of transmission, but examples of respiratory route exist Pathology-Cause a wide range of syndromes |
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Poliovirus infection
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90% asymptomatic
5% abortive - febrile illness - headache, sore throat, fever, malaise, vomiting 1-2% Non-paralytic poliomyelitis .1-2% Paralytic |
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Salk polio vaccine advantages
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dead virus
immunocomp safe good systemic immunity |
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Salk polio vaccine disadvantages
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multiple IM injections
expensive *less intestinal immunity |
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Sabin polio vaccine advantages
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oral
both systemic and intestinal immunity |
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Sabin polio vaccine disadvantages
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neurovirulent revertion
no immunocompromised |
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OBSTACLES FOR POLIO ERADICATION
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-Political
-Geographical barriers -Long-term shedding of live vaccine viruses in immunocompromized individuals -Laboratory stocks -Virus construction |
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RHINOVIRUSES
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-Major cause of mild upper respiratory tract infection
-Temperature sensitive - 33°c -Affects all age groups -No vaccine - >100 serotypes -No effective treatment |
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Coronaviruses
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-Second most prevalent cause of the common cold
-SARS |
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Noraviruses
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-Epidemic gastroenteritis
-Most important cause of diarrhea in adults -Oral transmission -Short duration, self-limiting |
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How fast do you see symptoms after ingestion of Norwalk virus?
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24 hours
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ORTHOMYXOVIRIDAE
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Negative sense RNA genome
**Segmented genome RNA replication in nucleus |
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What are the three types of Influenza?
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-Influenza A - 8 segments - humans, birds, pigs, horses, and aquatic mammals can all act as hosts
-Influenza B - 8 segments - humans -Influenza C - 7 segments - humans |
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Influenza A
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viruses generally cause greatest disease problems
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Influenza B
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causes similar disease symptoms and during occasional years are the most prevalent
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Influenza C
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causes mild disease symptoms by comparison
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hemiagglutin (HA)
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-responsible for initial interaction and plays role in uncoating the virus
-change in structure required to bind to membrane-due to fusion pH |
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Neuraminidase (NA)
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occurs at the end of cycle and plays a role in release of the newly formed virus
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M2
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protein channel that allows H+ in cell that lowers the pH and activates HA
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who dies from the flu?
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old and young
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da FLU illness
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Fever
Myalgia Headache Shaking chills Cough Secondary bacterial infection and pneumonia can seriously increase consequences |
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when do you see the flu and how many people are affected?
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winter months
10% of the population |
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What is the incubation time for the flu?
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Brief incubation period, ~2 days abrupt onset
2 - 5 days of maximum illness |
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What types of immune response does the flu trigger?
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antibody-T-cell
interferon |
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What are some serious complications of the flu?
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secondary bacterial infection
primary viral pneumonia CNS, muscle involvement |
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What are the major contributors to pathogenesis of flu?
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1. aerosol inoculation
2. replication in respiratory tract 3. desquamation of mucus secreting cells |
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How do you detect flu early?
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lab methods that detect virus in respiratory secretions
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Why is it advantageous for the flu to occur in aquatic waterfowl?
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Continuously circulate, many of the birds are migratory
Do not cause disease Perfect natural reservoir |
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What flu subtypes have caused pandemics in humans?
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H1 subtype - 1918 pandemic (h1n1)
H2 subtype - 1957 pandemic (h2n2) H3 subtype - 1968 pandemic (h3n2 |
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Antigenic drift
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Mutation in surface proteins that enables virus to escape from currently circulating antibodies
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Antigenic shift
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Reassortment of segments of the viral genome
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What is the mechanism of reassortment in flu?
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duck and human virus combine in flu to make new strains in pigs that are transmitted to humans
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1997 AVIAN INFLUENZA
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Limited outbreak in hong kong
Highly pathogenic 18 confirmed cases All required hospitalization 6 fatalities |
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2004 H5N1 outbreak in southeast Asia
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Highly pathogenic
238 human cases confirmed - vietnam, thailand, china - 139 fatalities Direct transmission from birds Killed wild birds as well as chickens Human incidence decreased recently |
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Why did the human incidence of H5N1 decrease recently?
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Decrease in host population? - >100 million birds died due to natural exposure or slaughter
Normal decline due to seasonal variation |
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Defining Characteristics of Retroviruses
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-2 enveloped RNA virus
-virion associated RT -DNA Provirus integrated -rapid evolution via error prone RT |
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what are the three main genome segments of HIV?
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gag
pol env |
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Which genome segment is a target for therapy?
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pol- contians the top 3 targets for therapy RT, integrase, and protease
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What genes do the env segment give rise to?
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gp120-glycoprotein on the envelope
gp41-matrix protein these would be primary targets for a vaccine |
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Flow of Genetic Information in Retroviruses
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virion rna is reverse transcibed into provirus which is subsequently integrated into the genome. From here, everything is transcribed and such.
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Simple Retroviruses
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Contain only gag, pol, (pro) & env protein coding regions
e.g. Avian Leukosis Virus (ALV) |
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Complex Retroviruses
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Contain additional accessory genes
Pathogenicity Gene Regulation Multiple mRNA splice sites e.g. HIV *ALL human retroviruses are complex |
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which retroviruses are responsble for human t cell leukemia?
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HTLV-I, II (complex)
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What genus is the HIV virus?
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lentivirus
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What types of disease can retrovirueses cause?
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tumours
wasting and auto-immune diseases immunodeficiency syndromes aplastic & haemolytic anaemias |
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what are the four human retroviruses known?
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HIV I-AIDS
HIV II-AIDS HTLV-1-T cell leukemia, tropical spastic paraparesis HTLV 2-no known pathology |
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what triggered the discovery of human retrovirus?
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ability to culture t cells in vitro-1980
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What do all human retroviruses infect?
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CD4 T cells
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T-cell leukaemia/lymphoma
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-Aggressive tumour of CD4 -cells infiltrates skin & brain
-only produced after a prolonged latent period. -Malignant change is the result of viral genome insertion changeing gene reg. -Less than 1% develop this malignancy. |
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Tropical spastic paraparesis
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Aggressive non-demyelinating spastic paraparesis.
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Epedemiology of HTLV-1?
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-Japan,Caribbean, West Africa
-prevalence increases with age -family clustering -spread via blood transfusion & sexual intercourse, breast feeding |
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How do you diagnose HTLV-1?
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HTLV-1 specific antibody, ELISA
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Lentiviruses & Persistence
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ability of these viruses to evolve in response to biological, immunological & pharmacological selective pressures with a remarkable array of genetic & antigenic variations
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How does the HIV envelope allow it to escape from effective antibody response?
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sequence evolution
sheilding of receptor binding sites extensive glycosylation |
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Gp120/ CD4/ Co-Receptor Interactions
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gp120 binding sites are block for both CD$ and chemokine
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Which viruses are responsible for the HIV epidemics?
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HIV-1-SIV Chimp
HIV-2-SIV sooty mangabey |
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HIV Transmission
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Inoculation in blood
Sexual Transmission Perinatal transmission (intrauterine and brestfeeding) |
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What is the main predictor of risk of transmission?
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HIV load
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When is infectivity highest?
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primary infection - high viremia
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What factors enhance transmission?
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Ulcerative STDs & lack of male circumcision
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What are the stages of HIV infection?
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seroconversion
asymptomatic HIV progression AIDS |
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What cells does HIV target?
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Th cells
macrophages-facilitate persistence dendritic cells-capture and present HIV chemokine receptors CCR5 and CXCR-4 |
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CCR5 ligands
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RANTES, MIP-1a, MIP-1b
Homozygous mutants of CCR5 are resistant to infection |
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CXCR4 ligands
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SDF-1
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what are the main sites of HIV replication?
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Primary Lymphoid Organs
Secondary Lymphoid Organs CNS |
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What are circumstances of immune activation that faciltate HIV replication?
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proliferation of CD4 cells is a requirement for RT and nuclear transport
upregulation of CCR5 and enhanced expression of provirus in activated t cells |
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What things can you use to test for HIV
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antibodies
antigens virus |
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how can you test for antibodies?
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ELISA
Confirmation by Western Blot Traditionally done with serum; may be done with saliva |
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how can you test for antigens?
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ELISA based assay for p24 which is detected in blood before antibodies
used with ELISA to screen lood supply |
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how can you test for virus?
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Quantitative RT-PCR(standard)
Qualitative PCR for DNA Virus isolation by culture used infrequently |
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How would you recognize a primary HIV infection?
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symptoms of influenza infection or acute mononucleosis
high transient viremia |
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What resolves the primary peak in the primary infection and how long does it last?
|
peak is resolve by CD8 cells
antibody response in 3-5 weeks Quasi-steady state set-points in viral load are reached in 3-12 months |
|
|
After seroconversion, what predicts variable progression to AIDS?
|
set point HIV RNA values
|
|
|
What is the relationship between CD4 count and HIV replication?
|
inverse
|
|
|
What is the clinical importance of viral load measures?
|
strongly predictive of disease progression
standard of care for decisions regarding initiation of therapy essential for monitoring therapy |
|
|
Clinical ‘Latency’ Period
|
Approximately constant viral loads
CD4+ T cells decline slowly No apparent symptoms highly dynamic state with high levels of turnover |
|
|
How long does is take on average for people to progress to AIDS?
|
about 10 years
|
|
|
when do you see onset of symptoms and what are they?
|
CD4<400
mucosal candidiasis herpes infection |
|
|
What do you see with full blown AIDS?
|
CD4<200
KS PCP MAC(<40) Severe CMV(<40) Dementia, malignancies |
|
|
Protozoal indicators of AIDS
|
Toxoplasmosis of the brain
Cryptosporidiosis with diarrhea Isoporiasis wih diarrhea |
|
|
Fungal indicators of AIDS
|
Candidiasis of the esophagus, trachea, and lungs
Pneumocystis carinii pneumonia Cryptococcosis Histoplasmosis Coccidiodomycosis |
|
|
Viral indicators of AIDS
|
CMV
Herpes Progressive multifocal leukoencephalopathy Hairy oral leukoplakia caused by EBV |
|
|
Bacterial indiators of AIDS
|
Mycobacterium avium (MAC) Tuberculosis
Salmonella septicemia Pyrogenic bacterial infections |
|
|
OPPORTUNISTIC NEOPLASIAS indicators of AIDS
|
Kaposi’s sarcoma
Primary lymphoma of the brain Other non-Hodgkin’s lymphomas |
|
|
Other indicators of AIDS
|
HIV wasting syndrome
HIV encephaolpathy Lymphoid interstitial pneumonia |
|
|
What are the most likely indicator conditions in AIDS?
|
Severe HIV-related immunosuppression-85
PCP-16 HIV wasting syndrome-8 Esophageal candidiasis-6 M. Tuberculosis infection-3 |
|
|
How does HIV directly cause AIDS?
|
Lysis of infected cells(virus effect)
|
|
|
How does HIV indirectly cause AIDS
|
Host response-
-Apoptosis of bystander cells -Impaired T cell regeneration -Disruption of lymph nodes structure/function -CTL killing of infected cells |
|
|
How much is virus turnover in the clinical latency period?
|
10^10 virions produced each day
|
|
|
Besides CD4, what are the other immune perturbations in HIV?
|
CD8 T cell activation: inc. CD38, dec. CD28
Apoptosis of CD4 and CD8 T cells Naïve T cell loss, effector memory T cell increase Altered lymph node, thymus and bone marrow Altered T cell kinetics: inc destruction, dec. production |
|
|
What is the exception to CD4 count and viral load being inversely related?
|
SIV infection in sooty mangabeys the CD4 count stays high regardless of high viremia
|
|
|
What leads to increased destruction of CD4?
|
direct effect of virus and increased bystander cell death as a result of inappropriate apoptosis
|
|
|
Anti-HIV immune responses
|
Total antibody
Neutralizing Antibody CTL Inhibition of viral entry by b-chemokines Pro-inflammatory cytokines (IFN-g, TNF-a) |
|
|
Basic Principle 1
|
Infectious diseases are caused by microorganisms that differ from us both structurally and functionally
|
|
|
Basic Principal 2
|
Structural and functional differences of microbes provide targets for antimicrobial chemotherapy
|
|
|
Koch’s postulates
|
Isolate the pathogen in pure culture
Introduce the pathogen into a susceptible animal host and observe the disease Isolate the pathogen in pure culture from experimentally infected animal Always isolate the pathogen from humans with the disease |
|
|
Koch’s molecular postulates
|
Phenotype should be more often associated with pathogenic strains of a species
Specific inactivation of the gene should decrease virulence or result in loss of a property in a cell or animal model system Restoration of the wild-type gene restores virulence |
|
|
What is the leading cause of bacterial meningitis in the United States ?
|
Streptococcus pneumoniae
|
|
|
Which form of bacterial meningitis shows the highest mortality in the US?
|
Streptococcus pneumoniae
|
|
|
How do we identify bacteria?
|
morphology
differential staining biochemical characteristics |
|
|
Cocci
|
-shperes
-streptococci-division in one plane and grows in chains -staphylococci-division in multiple planes |
|
|
baccilli
|
-rods
-bacillus anthracis-appear as single rods -listeria monocytogenes-oval coccobacilli |
|
|
Gram Stain
|
1.crystal violet
2. iodine 3. alcohol wash 4. safranin + dark blue - pink |
|
|
Acid fast stain
|
Red dye carbol fuchsin applied to fixed smear
Slide heated acid/alcohol mixture -Acid fast organisms retain dye because it is more soluble in the cell wall lipids than in the acid/alcohol mixture |
|
|
Acid fast stain is used to identify which bacteria?
|
mycobacteria spp.
|
|
|
What are hemolysis reactions?
|
performed by doing a liquid or solid culture onto a petri dish and checking for a response.
|
|
|
“alpha” hemolysis
|
Green due to the production of biliverdin from heme. S. pneumonia will give this result
|
|
|
“beta” hemolysis
|
The complete lysis of RBCs around the colony
|
|
|
“gamma” hemolysis
|
absence of any hemolytic activity
|
|
|
selection test
|
selects for particular bacteria of interest and selects against those that we don’t care about (ex: antibiotics in the media that kill sensitive bacteria while resistant bacteria grow)
|
|
|
Differential/selection for S. aureus
|
Mannitol salt agar has a very high concentration of NaCl so that only Staphylcocci grow.
To distinguish S. aureus from all of the other Staphylococcal species add mannitol (a sugar) and a pH indicator. S. aureus will ferment mannitol while secreting lactic acid causing the pH to become acidic and the indicator will change color (from red to yellow). On the left is S. aureus and on the right is some other type of Staphylococcal bacteria. |
|
|
MacConkey agar
|
Bile salts select for growth of enteric bacteria, lactose plus pH indicator identify lactose fermentation (red) indicating Escherichia coli
|
|
|
Polymerase chain reaction
|
rapid and sensitive identification of bacteria without having to do a culture.
Can be done for speices or strain Also can be used to compare sequences |
|
|
DNA – DNA hybridization
|
defines bacterial species
If DNA preparations from two bacteria show 70% hybridization and half the hybridizing DNA melts within a 5°C increase in temperature, the bacteria belong to the same species |
|
|
virus definition
|
-Sub-microscopic, obligate intracellular parasite
|
|
|
Viroids
|
small (200-400 nucleotides) circular RNAs with a rod-like secondary structure which possess no capsid or envelope and are associated with certain plant diseases
|
|
|
Virusoids
|
satellite viroid-like molecules, slightly larger, which are dependent on the presence of virus replication for multiplication, which allow them to be packaged into virus capsids as passengers
|
|
|
Prions
|
infectious agents believed to consist of a single type of protein molecule with no nucleic acid component (e.g., Creutzfeldt-Jakob disease)
|
|
|
viral capsid
|
encloses viral genome
protects genome from physical(shear), chemical(UV), and enzymatic damge(nuceases or antiviral). protein subunits are redundant |
|
|
outer envelope
|
lipid bilayer containing viral glycoproteins (and in some cases cellular glycoproteins – e.g., HIV) – however, many viruses lack an envelope
|
|
|
outer surface
|
involved in binding/recognition of the host cell
|
|
|
viral structure is icosahedral
|
naked viruses tend to be stable and to resist dessication, acid, and detergent
fecal/oral Geometry determines the size of the genome that can be packaged inside the capsid |
|
|
What determines viral classification?
|
morphology including size, shape, capsid symmetry, envelope, and viron properties
|
|
|
What are the top two factors to classify a virus?
|
genome
envelope |
|
|
what is the difference between positive and negative RNA?
|
negative contains the complement RNA and must be copied by a viral RNA plymerase in order to produce mRNA
|
|
|
Which DNA viruses have an envelope?
|
pox
herpes hepadna |
|
|
Which DNA viruses are NAKED?
|
parvo
polyoma papilloma adeno |
|
|
Which RNA viruses have an envelope?
|
toga
flavi corona rhabdo filo orthomyxo paramyxo arena retro |
|
|
Which RNA viruses are NAKED?
|
picorna
noro |
|
|
Which RNA virus has a double capsid?
|
REO
|
|
|
What are the stages of viral growth?
|
infection
eclipse latent lysis |
|
|
Why would catheterization predispose to infection?
|
Provide access to defended site, introduce infecting organisms, block defenses
|
|
|
Where did the infecting microorganisms come from?
|
Normal flora, nosocomial infection
|
|
|
What is sepsis and what is its cause?
|
Clinical condition due to systemic effects of inflammatory responses, bacterial toxin esp. endotoxic products
|
|
|
How does sepsis cause death?
|
Vasodilation, DIC, organ failure
|
|
|
How did the pope die?
|
Organ failure due to sepsis following urinary tract infection
catheterization infection sepsis death |
|
|
Virulent bacteria
|
Have the capacity to grow at the expense of the host
|
|
|
Opportunistic bacteria
|
Exploit preexisting conditions in the host
|
|
|
Virulence factors
|
Enhance the ability of the bacteria to cause disease
Not all strains of a particular species express the same virulence factors |
|
|
what factors prevent entry and spread of bacteria?
|
Integrity of skin
Mucus Ciliary action Fluid flow Secretions (lysozyme, bile) Temperature |
|
|
What factors affect colonization, adhesion, and invasion?
|
Temperature
pH Adhesins Invasins/manipulation of actin cytoskeleton Biofilm formation |
|
|
what determines the disease a bacteria causes?
|
how the bacteria gained entry and where it ended up
|
|
|
How does bacteria cause tissue destruction?
|
Hemolysins, lipases (membranes)
Collagenase, protease, hyaluronidase (CT) Dnases Provision of nutrients? |
|
|
Is LPS an endotoxin or exotoxin?
|
endo
|
|
|
Is diptheria toxin an endo or exotoxin?
|
exotoxin
|
|
|
How does diptheria toxin cause disease?
|
b unit allow translocation where the catalytic subunit A causes cell death by inactivatiing EF-2
|
|
|
Is cholera an endo or exotoxin?
|
exotoxin
|
|
|
How do cholera work?
|
cholera releases its toxin wbinds to a ganglioside receptor triggering a cAMP dependent loss of cell nutrients leading to diarrhea
|
|
|
Is tetanus endo or exo?
|
exotoxin
|
|
|
How does tetanus work
|
toxin is a n endopeptidase that inhibits release of inhibitory transmitter allowing only contiuouw stimulation by excitatory transmitters leading to spastic paralysis
|
|
|
Is botylism endo or exo?
|
exo
|
|
|
How does botylism work?
|
toxin blocks the release of ACH vesicles causing flaccid paralysis
|
|
|
What is the most important virulence factor enabling bacteria to escape host defenses?
|
capsules because they inhibit phagocytosis and opsonization by hiding surface antigens from antibodies.
|
|
|
what causes gas gangrene?
|
Clostridium perfringens
|
|
|
What determines tropism in viral infection?
|
receptor specificity
|
|
|
What is the most common route of viral infection?
|
inhalation
|
|
|
Arbovirus
|
it is not a virus but implies spread by arthropod vector
|
|
|
Outcome of infection of a cell
|
Failure to infect
cell death infection syncytia formation apoptosis oncogenesis |
|
|
What are the ways viruses can be oncogenic?
|
remove growth inhibition
activate growth stimulation prevent apoptosis |
|
|
Flu-like systemic symptoms
|
Interferon, cytokines, C3
Respiratory viruses |
|
|
Delayed type hypersensitivity
|
T cell responses
Enveloped viruses |
|
|
Immune complex disease
|
Antibody, complement
Hepatitis B |
|
|
Hemorrhagic disease
|
T cell, antibody, complement
Filoviruses |
|
|
Immunosuppression
|
HIV, cytomegalovirus, measles, influenza
|
|
|
Susceptibility/severity of disease depends on what?
|
Nature of exposure
Immune status Viral dose |
|
|
T or F Most viral infections cause disease
|
F
|
|
|
how do bacterial cells differ from eukaryotic cells?
|
Transcription, translation and DNA replication all take place in the same intracellular compartment
|
|
|
prokaryotes
|
smaller, no mitochodria, 70/50/30 ribosomes, no sterols, and respiration takes place in cytoplasmic membrane
|
|
|
Bacterial chromosome
|
Circular
Organized into ~ 50 domains ~1 mm long (500x length of the bacterium) Domains are supercoiled |
|
|
what bacteria has a linear chromosome?
|
borellia spp
|
|
|
plasmids
|
Extrachromosomal genetic elements
Capable of autonomous replication |
|
|
how do gram +/- membranes differ?
|
negative-has an outer membrane with less murein underneath
the outer membrane block the cresyl violet stain |
|
|
What gives bacteria their shape
|
Peptidoglycan: glycan chains joined by peptide crosslinks
Murein: peptidoglycan containing muramic acid |
|
|
Gram-positive cell wall
|
Single membrane
Multiple layers of peptidoglycan (murein) Teichoic and lipoteichoic acids: polyribitol and glycerol phosphates (antigenic determinants, adherence, movement of cations, gram-positive sepsis) |
|
|
Gram-negative cell wall
|
Outer and inner membrane
Single layer of peptidoglycan Lipoprotein (attaches outer membrane to peptidoglycan) Lipopolysaccharide Porins (small compounds diffuse across outer membrane) |
|
|
Mycobacterial cell wall
|
Mycolic acids
Lipoarabinomannan Porins (aid diffusion through hydrophobic layer) |
|
|
Gram + tetrapeptides and cross links
|
pentapeptide precursor: L-ala – D-glu – L-lys – D-ala – D-ala
cross link: L-lys – (gly)5 - D-ala |
|
|
Gram - tetrapeptides and cross links
|
pentapeptide precursor: L-ala – D-glu – dap – D-ala – D-ala
cross link: dap – D-ala |
|
|
Lipopolysaccharide
|
Extremely toxic
Causes fever and shock Blocks diffusion of hydrophobic and hydrophilic compounds(requirement for porins) O antigen side chains are major surface antigens (no teichoic acids) e.g. E. coli O157:H7 |
|
|
movement of flagella
|
random
directed(chemotaxis) |
|
|
What are the types of pili?
|
Common pili or fimbriae-carry adhesins, mediate attachment, twitching motility
Sex pili-mediate attachment to other bacteria during conjugation |
|
|
What is important about pili?
|
facilitate bacterial protein secretion
|
|
|
Capsule
|
Usually made of polysaccharide
Produced by both gram-positive and gram-negative bacteria Resistance to phagocytosis Quellung reaction |
|
|
What is the quelling reaction?
|
capsule specific antibody that causes capsule to swell forming a white halo on slide
|
|
|
Glycocalyx
|
General term for substances that surround cells
|
|
|
What are the functions of glycocalices?
|
Adherence – biofilm formation, adherence to tissues
Protection from phagocytosis |
|
|
What is the glycocalx called when it is attached to the cell wall?
|
capsule--slime if not
|
|
|
Endospores
|
formed by + rods
Small, dehydrated, metabolically quiescent can withstand extemes, chemicals, and radiation external layer is made of lipoprotein/carb) |
|
|
What are the steps of endospore formation?
|
1. septum isolates DNA
2. plasma membrane forms 3.septum surrounds spore 4.peptidoglycan layer forms 5.spore coat 6. endospore released |
|
|
In rich broth, how often do bacteria double?
|
every 30 minutes
|
|
|
Bacterial growth curve
|
lag
exponetial stationary death |
|
|
Log phase
|
Exponential growth in the presence of excess nutrients
|
|
|
Stationary phase
|
Nutrient exhaustion leading to many complex adaptations
-sporulation -Competence for genetic transformation -Survival under starvation conditions REDUCED EFFECTIVENESS OF ANTIMICROBIALS |
|
|
Aerobic respiration
|
1 molecule of glucose generates 2 ATP molecules by glycolysis and 2 ATP molecules from the TCA cycle
The NADH and FADH2 lead to the production of 34 ATP molecules by electron transport and chemiosmosis |
|
|
Toxic forms of oxygen
|
Singlet oxygen (O2)
Superoxide free radicals (O2.-) Peroxide anion (O2 2-) |
|
|
Singlet oxygen
|
Molecular oxygen in a high energy state (phagocytic cells)
|
|
|
superoxide free radicals
|
Produced when oxygen is terminal electron acceptor
Requires superoxide dismutase (SOD) for neutralization |
|
|
Peroxide anion
|
Catalase-h2o and o2
Peroxidase-just h2o |
|
|
What determines whether oxygen is useful to a bacteria?
|
enzymes present
|
|
|
Obligate anaerobes
|
O2 required
catalase and SOD |
|
|
facultative anaerobes
|
greater growth in the presence of oxygen
catalase and SOD |
|
|
obligate anaerobe
|
oxygen stops growth
lacks enzymes |
|
|
aerotolerant anaerobes
|
only anaerobic growth but continues in the presence of oxygen
SOD |
|
|
microaerophiles
|
only aerobic growth in low conc of oxygen
produce too much toxic oxygen |
|
|
What is the purpose of fermentation?
|
Fermentation restores NAD+
|
|
|
How do bacteria acquire nutrients?
|
Secretion of degradative enzymes
Transport into the cell Secretion of compounds that bind nutrient followed by uptake |
|
|
Iron uptake
|
Concentration of free iron vanishingly small (transferrin, lactoferrin, ferritin)
Bacteria obtain iron either by chelating agent or by special receptors that extract iron from cells and transport it into cells. |
|
|
sterilization
|
destruction of all forms of life
ususally done under pressure or with ethylene oxide |
|
|
commercial sterilization
|
sufficient heat to kill endospores of clostridium botulinum in canned food
|
|
|
disinfection
|
destruction of vegetative pathogens
can use phyiscal or chemical methods |
|
|
antisepsis
|
destruction of vegetative pathogens on living tissue
always by antimicrobial chemicals |
|
|
degerming
|
removal of microbes form limited area such as skin around infection
mostly mechanical with alcohol swab |
|
|
sanitization
|
treatment intended to lower microbial count on eating and drinking utensils
high temp washing or by dipping into chemical disinfectant |
|
|
Disinfection of living tissue
|
handwashing-<1 log
hand disinfection(more effective presurgical skin disinfection-iodine is only one approved, friction greatly increases difference in killing |
|
|
Thermal death point (TDP)
|
Lowest temperature at which all organisms in a liquid sample will be killed in 10’
|
|
|
Thermal death time (TDT)
|
Minimum for everything to die at a given temperature
|
|
|
Decimal reduction time (DRT or D value)
|
Time in which 90% of a population will be killed at a given temperature
|
|
|
What factors affect effectiveness of antimicrobials?
|
Number of organisms – larger number, longer to eliminate the population
Environmental factors – organic materials reduce effectiveness, serum binding proteins, biofilms,temperature Time of exposure |
|
|
Pasteurization-High temperature short time (HTST) pasteurization
|
High temperature short time (HTST) pasteurization
72ºC, 15” for milk – milk must still be refrigerated |
|
|
Ultra high temperature (UHT) treatment
|
140ºC, 1” – milk can be stored without refrigeration
|
|
|
disk diffusion assay
|
used to evaluate disinfectants by plating them with various bugs and measuring the zone of inhibition
|
|
|
why are phenols modified?
|
to reduce irritation or increase antibacterial action in combination with a detergent
|
|
|
what is the main ingredient in lysol?
|
O-phenylphenol (cresol) main ingredient in Lysol
|
|
|
What can kill staphylococci and streptococci?
|
Hexachlorophene – pHisohex
|
|
|
Quaternary ammonium compounds
|
Hydrogens of the ammonium ion replaced
Zephiran – benzalkonium chloride Cepacol – cetylpyridinium chloride Neutralized by soaps and and anionic detergents Pseudomonas actively grow on quaternary ammonium compounds |
|
|
Halogens
|
iodine and chlorine
|
|
|
iodine
|
tincture (solution in aqueous alcohol)
iodophore (combination of iodine and organic compound) Betadine |
|
|
Chlorine
|
Chlorine + water yields hypochlorous acid (strong oxidizing agent)
Sodium hypochlorite – Clorox Sodium dichloroisocyanurate – Chlor-Floc (chlorine + flocculating agent) Chloramines – water treatment |
|
|
Peroxygens
|
Ozone – supplement to chlorination
Hydrogen peroxide – not good on open wounds (catalase), effective on surfaces Benzoyl peroxide – acne medication, anaerobic bacteria Peracetic acid – liquid sporicide |
|
|
List bugs in order of most to least resistant?
|
endospores, mycobacteria, protozoa, gram -, fungi, nonenveloped virus, gram +, enveloped virus
|
|
|
What works best on endospores?
|
chlorines and glutaraldehyde
|
|
|
What works best on mycobacteria?
|
phenolics, iodine, alchohols, and glutaraldehyde
|
|
|
Therapeutic index
|
ratio of toxic to therapeutic dose
|
|
|
which are easier to kill--bacteria or virus?
|
bacteria-bc they are different
|
|
|
What are unique targets that make things easier to kill?
|
Cell wall biosynthesis
Different ribosomes Different RNA polymerase Different DNA polymerases |
|
|
Selective toxicity
|
kills the bugs without killing us
|
|
|
acyclovir
|
only effective in infected cells
Must be metabolized by viral encoded thymidine kinase Not a substrate for the cellular thymidine kinase |
|
|
Bactericidal drugs
|
(e.g. beta-lactams) kill bacteria (only growing bacteria) without the action of the humoral or cellular immune response
|
|
|
Bacteriostatic drugs
|
prevent growth of susceptible bacteria, but they must be killed by the host’s defenses
|
|
|
What effect does biofilm growth have on effectivness of antibiotic therapy?
|
can dramatically reduce it
|
|
|
Minimal inhibitory concentration (MIC)
|
Least amount of antibiotic required to prevent growth of the bacteria under standard
|
|
|
How is MIC measured?
|
Serial dilutions of antibiotic each with a standard inoculum
or Disk diffusion assays Diameter of the zone of inhibition related to the MIC |
|
|
Minimum lethal concentration (MLC)
|
Least amount of antibiotic required to kill a predetermined fraction of the bacteria (99.9%) in a given time
|
|
|
What is the key for an effective antibiotic therapy?
|
levels of antibiotic at the site of infection must be above the MIC
|
|
|
What factors determine the MIC at the site of infection?
|
Absorption from the upper gastrointestinal tract
Is the compound excreted or concentrated in the urine How rapidly is the compound metabolized How strongly does the compound bind to protein |
|
|
serum binding of antibiotic
|
leads to a more prolonged but lower concetration
|
|
|
Spectrum of activity
|
The spectrum of an antibiotic activity is the range of organisms against which the antibiotic is effective
|
|
|
benzyl penicillin
|
narrow spectrum
active against gram-positive and gram-negative cocci but not gram-negative bacilli |
|
|
chloramphenicol or tetracycline
|
broad spectrum
active against a wide range of gram-positive and gram-negative bacteria |
|
|
How do penicillin and aminoglycosides synergistically work against enterococci?
|
Penicillin affects cell wall synthesis, increasing penetration of the aminoglycoside (protein synthesis inhibitor)
|
|
|
Why do bacteriostatic drugs and penicillin antagonize each other?
|
Penicillin only active against growing cells
|
|
|
when do you use dual therapy?
|
high numbers (pulmonary TB)
resistance to a single drug at 10^-6-frequency of resistance to 2 drugs is rare |
|
|
How would you treat pulmonary TB?
|
isoniazid and rifampicin
|
|
|
what are the most important drugs that inhibit peptidoglycan synthesis?
|
The most important are the beta-lactams (penicillins and cephalosporins) and the glycopeptides (vancomycin)
|
|
|
Penicillins
|
Inhibit cell wall bisynthesis
Low toxicity (except for hypersensitivity reactions) Example of beta-lactam antibiotics Susceptible to cleavage by penicillinases (beta-lactamases) |
|
|
Action of penicillin
|
Penicillin inhibits transpeptidation
Structure of penicillin very similar to terminal D-ala-D-ala of peptidoglycan precursor |
|
|
Narrow spectrum (penicillin V)
|
active against gram-positive organisms, some gram-negative cocci, some spirochetes (treponema)
not active against Gram-negative bacilli (outer membrane) |
|
|
Penicillinase-resistant (nafcillin, oxacillin)
|
active against beta-lactamase producing S. aureus
|
|
|
Extended spectrum (ampicillin, carbenicillin)
|
Active against some gram-negative bacteria
Inactivated by staphylococcal beta-lactamase Greater activity against enteric bacteria and Pseudomonas spp |
|
|
β-lactam plus β-lactamase inhibitor (ampicillin/sulbactam)
|
Improved activity against beta-lactamase producing S. aureus
|
|
|
Cephalosporins
|
Contain beta-lactam ring
Resistant to staphylococcal beta-lactamases |
|
|
First generation (narrow spectrum)Cephalosporins
|
some gram-negative activity (E. coli, Klebsiella, Proteus mirabilis)
susceptible to gram-negative beta-lactamases |
|
|
Second generation (expanded spectrum)Cephalosporins
|
extend spectrum to anaerobes and more gram-negatives (Haemophilus)
|
|
|
Third generation (broad spectrum)Cephalosporins
|
extended gram-negative spectrum (Neisseria, Pseudomonas)
|
|
|
Fourth generation (extended spectrum)Cephalosporins
|
Most Enterobacteriaciae and Pseudomonas
|
|
|
Carbapenems(beta lactam)
|
-Imipenem
Highly resistant to most beta-lactamases Very wide spectrum of activity Rapidly hydrolyzed by renal tubular dehydropeptidase Therefore administered with inhibitor (cilastatin) |
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Monobactams (beta lactams)
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-Aztreonam
Little activity against gram-positives, anaerobes Highly resistant to gram-negative beta-lactamases Anaerobic superinfections and distortions of bowel flora less commmon than with broad spectrum beta-lactamases |
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Vancomycin
(Glycopeptides) |
Binds to terminal D-ala - D-ala of peptidoglycan precursor
Inhibits transglycosylation and transpeptidation Treatment of methicillin-resistant S. aureus (bacteria are resistant to penicillinase-resistant penicillins such as oxacillin) and of resistant enterococcal infections |
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Aminoglycosides
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Inhibitors of protein synthesis
Synergistic effects with beta-lactam antibiotics |
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Tetracyclines and chloramphenicol
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Protein synthesis inhibitors
Broad spectrum Pass through eukaryotic cell membranes Active against intracellular bacteria (Rickettsia, Chlamydia) |
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Macrolides (e.g. erythromycin)
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Protein synthesis inhibitors
Newer macrolides such as azithromycin and clarythromycin are active against Mycobacterium avium and Toxoplasma gondii |
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Inhibitors of nucleic acid sythesis
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Quinolones (e.g. ciprofloxacin)
DNA gyrase inhibitors Rifampicin (important antimycobacterial agent) RNA polymerase inhibitor |
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Folate inhibitors-Sulphonamides
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Sulphonamides
Useful for urinary tract infections Structural analogues of para-aminobenzoic acid (folate precursor) |
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Folate inhibitors-Trimethoprim
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Active against Pneumocystis carinii
Inhibits dihydrofolate reductase |
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What is the mutation rate of HIV?
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Mutation rate: ~1 mutation per 10,000 bp genome/replication cycle
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What is the recombination rate of HIV?
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Recombination rate: ~1 in 3 genomes arising from cells infected with 2 genetically distinct genomes
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Why is it challenging to find an effective antiviral against HIV?
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Extensive replication in vivo generates many viral variants, including those that differ in susceptibility to antiviral drugs, immune responses
Drug resistant variants may be present before therapy is initiated, ditto for immune escape variants |
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antiviral agents
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Nucleosides
Nucleotide Combination Nucleosides Protease inhibitors Non-nucleoside RT inhibitors Fusion inhibitor |
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What are the benefits of early HIV therapy?
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-Control of viral replication easier to achieve/maintain
-Delay or prevention of immunodeficiency -Lower risk of resistance -Possible decreased risk of HIV transmission |
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What are the risks of early HIV therapy?
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-Drug-related reduction in quality of life
-Greater cumulative drug-related adverse events -Earlier development of drug resistance -Limitation of future treatment options |
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What are the benefits of delayed HIV therapy?
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-Avoid negative effects on quality of life
-Avoid drug-related adverse events -Delay development of drug resistance -Preserve treatment options for the future |
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What are the risks of delayed HIV therapy?
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-Possible risk of immune system depletion
-Possible greater difficulty in suppressing viral replication -Possible increased risk of HIV transmission |
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Realities of ART
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Eradication of HIV not possible
Toxicities of HAART potentially limit therapy Viral suppression rates not uniformly excellent |
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Possible Causes of Treatment Failure
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Poor adherence
Pharmacologic factors Limited drug/regimen potency Host factors Drug resistance |
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Antiretroviral Drug Toxicities-Immediate
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Immediate: headaches, GI intolerance, rash, stomatitis, hypersensitivity reactions
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Antiretroviral Drug Toxicities-short term
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Short term: neutropenia, anemia, peripheral neuropathy, renal stones, hepatitis
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Antiretroviral Drug Toxicities-long term
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Long-term:
Hyperlipidemia,Hyperglycemia/ diabetes mellitus, Fat redistribution, lipodystrophy Lactic acidosis/ hepatic steatosis, Avascular necrosis of hip, osteopenia, Thrombotic events, ischemic heart disease |
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how do you decide when begin antiretroviral therapy?
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virologic and immunologic crit.
pt understands need for requirements, circumsances, and commitment involved first chance is best chance |
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Patient is symptomatic..tx?
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initiate rx
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patient is asymtomatic with CD4 less than 350
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offer rx
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patient is asymtomatic with viral load of >60,000
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offer rx
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patient is asymtomatic with viral load of <60,000 and >350 CD4
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observe
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Criteria for Changing Therapy
|
-<0.5 - 0.75 log10 reduction in plasma HIV RNA within 4 weeks or <1.0 log10 reduction within 8 weeks of initiating therapy
-Failure to suppress HIV RNA to undetectable levels within 4-6 months of initiating therapy -Repeated detection of virus in plasma after initial suppression to undetectable levels, suggesting the development of resistance -Any reproducible increase, 3-fold or greater, from the lowest point of HIV RNA not attributable to intercurrent infection, vaccination, or test methodology -Persistently declining CD4 cell numbers, as measured on at least two separate occasions -Clinical deterioration |
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Influenza antivirals-Amantadine and rimantadine
|
Acts at the level of viral entry by preventing acidification of virus interior in the endosome - dissociation of nucleocapsids from protein
Very effective antiviral Doesn’t act on all strains Mutants selected |
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Influenza antivirals- Neuraminidase inhibitors – oseltamivir (Tamiflu)
|
Acts at the level of virus release by inhibiting virus disemination
Reduces severity of infection, but only if administered early on Drug-resistant mutants are rare Expensive |
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What are the 2 categories of antivirals for herpes?
|
1.affect viral DNA polymerase directly: foscarnet (PFA)- active against all herpesviruses
2.nucleoside analogs that require phosphorylation by viral enzymes before being utilized by, and inhibiting, viral polymerase (acyclovir, gancyclovir, vidarabine, idoxuridine) |
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What are the antivirals used for herpes?
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HSV1,2: all nucleoside analogs
VZV: vidaribine CMV: gancyclovir EBV: none Herpes B virus: acyclovir |
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Vaccine for herpes?
|
only vaccine currently licensed is live attenuated VZV
subunit vaccines for HSV currently in human trials |
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What memory responsed enable vaccines to work?
|
Antibody-for acute infection
Cytotoxic T lymphocytes, T Cell Help-Needed to control chronic intracellular pathogens (Viruses,Gram-positive) bacteria |
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B cell memory responses
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T-dependent B cells - Persisting Ab plus anamnestic expansion.
T-independent B cells - Anamestic expansion |
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T cell memory response
|
Protection by anamnestic expansion
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What 3 types of CD4 T cell help support the establishment and expansion of memory responses
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Th1
Th2 Treg |
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What are the three things need for a vaccine response?
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Antigen to provide specificity and memory
Innate immunity to provide danger signals Co-stimulation to provide energy |
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How does the innate immunity provide danger signals?
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TLR
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What does costimulation provide energy for?
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provides nutrients for rapid differentiation and division by activating AKT (glucose transporter) and Tor and Pim 1/2 which are amino acid transporters
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What forms can the antiden be delivered as?
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Live attenuated vaccine
Killed whole Vaccine Purified protein or polysaccharide Conjugated polysaccharide Genetically engineered protein Recombinant viral or bacterial vector DNA Heterologous prime/boost |
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Heterologous Prime/Boost Vaccines
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DNA priming and live vector boosting
Priming with one live vector followed by boosting with another live vector Priming with DNA or a live vector followed by protein boosting Power: Immunity to the prime does not interfere with the boost |
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Assays used for Vaccine Development
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Challenge infection (death and morbidity)
Antibody (use ELISA to detect bound antibodies to measure neutralization.) |
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Assays used for Cellular Responses
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IFN-gamma ELISPOT
ICS CFSE Proliferation |
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Which vaccines have been withdrawn?
|
Rotavirus
Inactivated measles Inactivated respiratory syncytial virus |
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Links between Vaccines and adverse events that have been disproved
|
MMR - autism
Thimerosol – autism Hepatitis B - multiple sclerosis Haemophilus influenzae type B conjugate and hepatitis B - diabetes |
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Links that are unsubstantiated by research
|
Anthrax – Gulf War syndrome
DTP – Atopy Pediatric vaccines – sudden infant death |
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Cancers that could be prevented by vaccines
|
bladder-Shistosomiasis
Lymphoma-EBV Liver-hep b and c cervical-HPV stomach-H pylori |
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diseases that need vaccines
|
Respiratory Diseases
HIV/AIDS Diarrheal Diseases Tb Malaria measles worms schisto |
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bench to clinic
|
GMP/GLP manufacture
FDA – IND (investigational new drug approval) Phase I – Safety/Dose escalation Phase II – Regimen and dose to elicit the correlate for protection Phase III – Efficacy in at risk population Phase IV – Continued post licensure monitoring |
