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76 Cards in this Set
- Front
- Back
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What is the definition of a PATHOGENIC bacteria?
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One that is capable of causing disease in a normal host.
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What is required in order to prevent and treat pathogenic bacterial infection?
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Vaccines and antimicrobials
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What does the term Virulence refer to?
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The degree of pathogenicity
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What is an organism that is NOT associated with disease called?
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Saprophytic
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What is the term for an organism that lives in relationship with a host in a way that both are benefited by the association?
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Commensal
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What is the term for an organism that causes disease in a compromised host?
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Opportunistic pathogen
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What is a common saprophyte?
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Bacillus species
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What is a common commensal?
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Staphylococcus
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What are the 2 most common opportunistic pathogens?
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-Pseudomonas
-Staphylococcus |
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What bacteria have the potential to become opportunistic pathogens?
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Commensials - normal flora
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What are 2 important factors that determine the outcome of a bacterial infection?
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-Dose of infection
-Incubation period |
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What is especially dangerous about an incubation period?
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The individual is highly contagious but asymptomatic
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What are the FOUR PROPERTIES OF A SUCCESSFUL PATHOGEN?
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1. Finds correct portal of entry
2. Attaches and colonizes 3. Resists host defense 4. Damages the host |
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What is necessary for a pathogenic bacterium to successfully colonize the host?
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It must attach to specific host tissue.
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What 2 components of the host defense mechanism must the pathogen resist?
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-Nonspecific TLR/cytokine and macrophages
-Specific cell mediated T/B cells |
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What are the 2 main Mechanisms of Pathogenicity in microbes?
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1. Invasiveness
2. Toxigenicity |
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What is invasiveness?
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The ability to grow in the host
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What is toxigenicity?
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The ability to produce toxins
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What are 2 key points about inoculum that influence the virulence of a pathogen?
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-Portal of entry
-Normal flora |
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How does portal of entry affect the virulence of Salmonella infection?
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Inoculating by subcutaneous route results in a 200X more toxic infection than orally.
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How does normal flora affect the virulence of a pathogen?
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When mice are pretreated with Streptomycin and then given Salmonella orally, it is 30,000X more virulent bc of decreased normal gut flora.
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So why does oral inoculation result in a less virulent infection than subcutaneous? (2 reasons)
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-Stomach is acidic and Salmonella can't survive it
-Gut normal flora prevent colonization |
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When a microbe enters a host, what causes DAMAGE to the host?
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-Invasiveness - growth
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What about a Noninvasive microbe is pathogenic to the host?
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Toxigenicity
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As opposed to the localized damage caused by invasiveness, where does tissue damage from toxigenicity usually manifest?
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At sites distant from the portal of entry.
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What is one pathogenic microbe that causes localized infection but distant toxigenicity?
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Corynebacterium diphtheriae
-Localized infection in trachea -Toxin damages all major organs |
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What do we call the toxins that are produced by pathogenic microbes?
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EXOTOXINS
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What types of bacteria produce exotoxins?
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Both gram pos and neg
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What produces endotoxin?
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Only gram neg
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Which is heat labile?
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Exotoxins (they're protein)
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How are exotoxins immunogenic? (two ways)
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1. They can be neutralized by antibodies
2. They can elicit immune responses when given as a vaccine. |
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How are exotoxins converted into vaccines?
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By denaturing with formalin to convert them into toxoids.
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What is NOT a component of toxogenicity of exotoxins?
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Fever
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How much exotoxin is required to be toxic?
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Small amounts can do it - like micrograms!
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What are the 4 classes of bacterial toxins?
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1. Surface acting
2. Pore forming 4. A/B toxins 4. type III and IV secretion |
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How do Surface acting toxins work?
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By binding a cell surface receptor and transducing a signal to the host cell interior.
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What is an example of a surface acting toxin?
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Superantigen
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How do Poreforming toxins work?
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By adhering to the cell surface and polymerizing to form a pore, thru which nutrients then efflux.
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How do A/B toxins work?
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By binding a specific receptor to the Bdomain, being endocytosed, then delivering the catalytic A subunit to the host cell interior which damages it.
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How do type III and IV secretion mechanisms work?
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The bacterium itself has a little syringe on it that injects toxin into the host cell.
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Are bacterial toxins nonspecific?
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NO; they are unique and yield specific pathologies.
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What are 5 types of covalent modification to host macromolecules?
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-ADP-ribosylation
-Proteolysis -Glucosylation -Deamidation -Deadenylation |
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How are toxins typically formed?
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As PROTOXINS
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Why do bacteria secrete toxins in a protoxin form?
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Because it is stable to the environment.
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What are 4 methods of activating protoxins?
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-Proteolysis
-DTT -Urea -Nucleotides |
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What are the resulting molecules from diphtheria protoxin activation?
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Proteins A and B
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What is the A fragment?
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The catalytic component
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What is the B fragment?
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The binding component
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What toxin family is the Diphtheria toxin a member of?
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the ADP-ribosylating exotoxin family
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What is the structure of the diphtheria toxin?
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A + B
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What is the gene location of the diphtheria toxin?
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Lysogenic phage
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What is the mechanism of action of Diphtheria toxin?
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ADP-ribosylation and activation of elongation factor 2 (EF2)
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What does Diphtheria toxin adp-ribosylation of EF2 result in for the host cell?
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Inhibition of protein synthesis
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How many cases of Diphtheria were there yearly in the US before the vaccine? After?
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Before: 176,000
After: about 1 |
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Where is diphtheria still a major killer of children?
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In underdeveloped countries
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How much diphtheria toxin is required to be lethal to a nonimmunized person?
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A few micrograms
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What is the diphtheria vaccine?
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Formalin inactivated diphtheria toxin (a toxoid)
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Why is the diphtheria toxoid especially useful?
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It can be used as a conjugate vaccine when attached to H. flu type B
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What is the gene encoding diphtheria toxin encoded within?
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A beta phage
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What are two types of strains of Corynebacterium diphtheriae?
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-Nonlysogenic strains
-Lysogenic strains |
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What type of infection do NONlysogenic strains of C. diphtheriae produce?
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LOCALIZED in the upper resp tract - pseudomembrane
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What type of bacterial growth is seen in nonlysogenic C. diphth infections?
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Noninvasive
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What type of growth is seen in Lysogenic strains of C. diphtheriae infections?
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Also localized, noninvasive, but with systemic pathology due to the toxins.
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In what 4 organs is pathology seen due to lysogenic C. diphtheria toxins?
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-Heart
-Liver -Lung -Nervous system |
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What is death caused by C. diphtheriae due to?
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Cardiac failure
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How many domains does the diphtheria toxin have? What are they?
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Three:
A-catalytic B- Receptor binding -Translocation domain |
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Once the B-receptor domain binds to a cell surface, how does the diphteria toxin get into the host cell?
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Endocytosis
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What happens within the acidic endosomal environment?
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Dissociation of the Translocation and catalytic subunits and translocation of the catalytic subunit into the cytosol.
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What does the catalytic subunit do once released from endosomal vesicles in a host cell?
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ADP-ribosylates EF2 and inhibits protein synthesis.
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What is the ultimate result of protein synthesis inhibition?
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Death of the cell
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What are active cases of Diphtheria treated with?
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Antitoxin against the receptor binding domain
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Why can Antitoxin be detrimental to the patient?
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Because it's produced in horses and can cause anaphylaxis.
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When should patients that have been in contact with a Diphtheria infected individual be vaccinated?
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If their last vaccine was more than 5 years ago.
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For what pathogenic microbes are the vaccines made by formalin inactivation?
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-Diphtheria
-Tetanus |
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For what pathogenic microbe is the vaccine made by using whole killed bacteria?
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Bordatella pertussis
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Once a disease has been eradicated from a population, can you stop vaccinating individuals?
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No; they tried that in Russia and now people are getting diphtheria there again
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