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174 Cards in this Set
- Front
- Back
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If a patient presents with a paroxysmal cough, whoop, and post- tussive vomiting, what bacterial infection should we expect?
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B. pertussis
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What is the difference between the CDC and WHO clinical guidelines for pertussis?
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The clinical criteria of paraoxysmal cough for 14 (CDC) or 21 (WHO) days are used for making the diagnosis
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Describe B. pertussis.
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B. pertussis are small, nonmotile, aerobic Gram-negative rods
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Who are the reservoirs for B.pertussis?
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adults and adolescents are an important reservoir for this pathogen and are often the source of infection for infants
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How does pertussis attach to the respiratory cilia?
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Through a protein on the pili, called filamentous hemagglutinin
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How does pertussis toxin attack the respiratory cell?
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Pertussis toxin irreversibly inactivates the G i-protein complex via ADP ribosylation, resulting in prolonged stimulation of adenyl cyclase --> causing a rise in cAMP. Elevated cAMP levels increase cellular protein kinase activity
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Who are candidates for the pertussis vaccine?
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6 weeks to 6 years
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How is vaccination for pertussis performed?
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Acellular pertussis vaccine in combo with diphtheria and tetanus toxoids
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How are ciliated cells killed by pertussis?
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By a tracheal cytotoxin ( a peptidoglycan fragment)
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How are mucosal epithelial cells killed by pertussis?
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Via a hemolysin
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What organisms make up largely the majority of cases of acute exacerbation of chronic bronchitis?
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H. influenzae and S. pnuemoniae
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Describe Haemophilus species.
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small, Gram negative coccobacillary rods
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How are the Haemophilus species differentiated ?
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These species are differentiated primarily by their requirements for X (heme) and V (nicotinamide adenine dinucleotide) factors.
there are three groups : those that require V only ; those that require X only; those that require both |
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What does Haemophilus parainfluenzae require for nutrition?
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Species designated para require V factor only
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How do we differentiate between the two groups of H. influenzae?
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There are two different groups of H. infleunza as determined by the presence or an absence of a polysaccharide capsule.
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How many subtypes of H. infleunzae group 1 are there?
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There are 6 subtypes based on the particular polysaccharide capsule
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What type of capsule does H. influenzae have?
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Hib has a polyribitol phosphate capsule
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How many strains of H. influenzae has LPS in the cell wall?
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All of them
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A three year old child presents with fever, dyspnea, tachypnea, drooling, and inspiratory stridor, what disease should we immediately suspect?
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Epiglottitis
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What bacteria is the causative agent for epiglottitis?
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Hib
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Why are group 2 H. influenzae referred to as nontypeable H. influenzae?
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they cannot be serotyped with antisera to the polysaccharide capsules
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What strains of H. influenza cause the most disease in children?
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group 1
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What strains of H. influenza cause the most disease in adults?
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group2 (NTHi)
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What are the most common bacterial species found in adult patients with COPD?
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H. influenzae, S. pnuemonia, and Moraxella catarrhalis
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What property for the NTHi have that allows them to colonize the respiratory mucosa?
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They have IgA protease
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What time frame must you have cough with expectoration to qualify for chronic bronchitis
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Chronic bronchitis is associated with excessive tracheobronchial mucus production sufficient to cause cough with expectoration for a period of at least 3 months over a period of 2 years or more
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What antibiotics are recommended for treatment of acute exacerbation of COPD?
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The newer macrolide ie azithromycin and clarithromycin and cephalosporins
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What pathogen is most likely seen in post-influenza pneumonia?
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Streptococcus pneumoniae
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Describe Streptococcus pneumoniae?
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Gram positive, lancet- shaped diplococci
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What is the criteria for significant sputum Gram smear?
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Criteria for significant sputum Gram smear include less than 10 squamous epithelial cells per low power field, greater than 25 PMNs, and the presence of a single or predominant organism
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What is the difference between viridians streptococcus and S. pnuemoniae when plateled on sheep blood agar media?
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S. pneumoniae is Optochin sensitive and viridans streptococci is Optochin resistant
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Describe the growth that you would expect to see on sheep blood agar media with S. pnuemoniae.
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It yields alpha- hemolytic colonies that are catalase negative and Optochin sensitive.
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How are the serotypes of S. pneumoniae determined?
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based on the antigenicity of capsular polysaccharide (CPS)
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what season is colonization with S. pneumoniae common?
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Winter months
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What is the most common cause of community acquired pneumonia
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S. pneumoniae
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How does IgA protease assist bacteria in colonization?
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capsular serotype- specific secretory IgA antibody made by airway epithelial cells prevents bacterial adherence and colonization.
IgA protease degrades IgA antibody and favors mucosal colonization |
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How does S. pnuemoniae adhere to respiratory epithelium?
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Pneumococcal adhesins bind to GlcNac beta 1,3- Gal disaccharide groups on epithelial cell glycolipids; they also bind to platelet activating factor (PAF) receptors on epithelial cells
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What are the different stages of lobar pneumonia?
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Congestion
Red hepatization Gray hepatization Resolution |
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What stage of lobar pneumonia is characterized by the alveolar spaces that are packed with inflammatory exudates?
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Gray hepatization
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What stage of lobar pneumonia is characterized by extravasation of RBCs?
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Red hepatization
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What is the typical pattern of consolidation with pneumococcal pneumonia?
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Lobar consolidation
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How does lobar consolidation occur?
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The intra-alveolar exudates spread rapidly within a lobe and through the pores of Kohn
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What is the treatment of choice for pneumococcal pneumonia?
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A third generation cephalosporin plus a macrolide or a newer quinolone (levofloxacin or gatifloxacin)
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What is the most common cause of meningitis in adults?
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S. pnuemoniae
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What family does K. pnuemoniae belong to?
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K. pneumoniae is a member of the family of Enterbacteriae
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Describe K. pnuemoniae.
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short, plump, Gram negative
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What characteristics make K. pneumoniae antiphagocytic?
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K. pneumoniae has a prominent polysaccharide capsule that is a major virulence factor
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Where is K. pneumoniae considered part of the normal flora?
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GI tract
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K. pneumoniae is _____ fermenting, urease-______and indole-_____
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lactose fermenting
urease positive indole-negative |
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What types of people are at risk for a K. pneumoniae infection?
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Alcoholics and people with history of seizure disorders are at increased risk infection
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How does K.pneumoniae gain access to the lungs?
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Via oropharyngeal carriage ( common in Alcoholics) that are aspirated into the lung.
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How does the host defend against K. pneumoniae?
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It is dependent on phagocytosis by macrophages and PMNs and the bactericidal effect of serum
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How does K. pneumoniae protect itself against phagocytosis?
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The capsular polysaccharide (CPS) forms thick bundles of fibrillose structures covering the bacterial surface in massive layers that protect the bacterium from phagocytosis by PMNs
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How does K. pneumoniae protect itself from activation of complement components?
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The CPS inhibits the activation of uptake of complement components especially C3b, and causes antigenic mimicry by the selective deposition of C3b onto LPS molecules.
This results in the inhibition of the formation of the membrane attack complex (C59-C9) |
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What is the typical X-ray presentation of K. pnemoniae?
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Patchy distribution of opacity on chest xray
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What type of pneumonia is caused by Klebsiella?
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Bronchopneumonia caused by acute inflammatory infiltrates from bronchioles into adjacent alveoli
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What is the typical treatment of Klebsiella?
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Extended spectrum penicillins
third generation cephalosporin plus aminoglycosides quinolones |
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How is bacterial resistance built against Klebsiella
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Through the acquistion of transferable plasmids possessing genes for extended-spectrum beta-lactamases
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Who is likely at risk for nosocomial infections for Klebsiella?
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They are frequently involved with respiratory tract manipulations, such as tracheostomy and mechanical ventilation
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What antibiotics are excluded via resistance of transferable plasmids possessing genes for extended-spectrum beta-lactamases for treatment of Klebsiella?
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Third generation cephalosporins
Aztreonam Aminoglycosides |
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Why doesn't Mycoplasma react to gram stain?
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They have no cell wall
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What are the typical characteristics of atypical pneumonia?
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1. nonproductive cough
2. variable chest x-ray (patchy, diffuse infiltrates) 3. no bacteria seen on smear 4. no response to beta lactam antibiotics |
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Describe the plasma membrane for mycoplasma.
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It is a three layer outer membran that contains cholesterol
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What is the ideal way to confirm Mycoplasma pneumoniae?
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Microorganism- specific IgG antibody response
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What is the pattern in IgG antibody levels in Mycoplasma?
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There is a four fold rise in IgG antibody titers between acute and convalescent - phase specimens ideally obtained 2 to 3 weeks apart
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Where are mycoplasma outbreaks common?
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Among young adults, especially in crowded military and institutional settings
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What is the highest risk age group for mycoplasma?
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5 to 20 years
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What pattern of infections is common in households infected
by mycoplasma? |
In families, cases occur serially , with 2-3 week intervals between cases
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Why is a prolonged cough common for Mycoplasma infections?
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Bacterial adherance leads to inhibition of ciliary movement , resulting in the prolonged cough in this disease.
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How does mycoplasma adhere to cilia?
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Mycoplasma has filamentous tips that is composed of a network of interactive proteins, designated adhesins, and adherence-accessory proteins.
They cooperate structurally and functionally to mobilize and concentrate adhesins at the tip |
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How does mycoplasma cause hemolytic anemia?
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Mycoplasma produces hydrogen peroxide that can damage erythrocytes in uncommon cases
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How does Mycoplasma initially cause disruption to the respiratory mucosa?
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Through Hydrogen peroxide
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What are the serologic tests for Mycoplasma?
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cold agglutination
A four fold rise in IgG antibody titers between acute and convalescent -phase serum specimens |
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Who would most likely die from a mycoplasma infection?
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The elderly and those with sickle cell disease
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What is the drug of choice for mycoplasma?
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Either doxycycline or erythromycin
but newer macrolides (azithro or clarith) or fluoroquinolones (levo) are better tolerated |
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How long is the treatment of mycoplasma pnuemonia?
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14 to 21 days
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What % of patients infected with mycoplasma would you expect to find with cold agglutinin in their serum?
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30% to 60% of patients
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What is the effect of mycoplasma stimulation of T and B lymphocytes?
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It induces the formation of IgM autoantibodies which reacts with various tissues and antigen I on erythrocytes
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What is Stevens-Johnson syndrome?
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It is an extensive rash involving the mucous membranes and large areas of the body
It is associated with Mycoplasma pneumoniae |
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What is bacterial infection is associated with Stevens-Johnson?
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Mycoplasma pneumoniae
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How can Legionella be detected in the urine?
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Find the direct antigen in urine to detect Legionella pneumophila serogroup 1
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Describe Legionellae.
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They are motile, flagellated, pleomorphic rods that stain faintly with Gram Stain
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Legionella is Gram ____
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negative
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What is the preferred stain for Legionella?
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Dieterle silver
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What is the definitive method of diagnosis for legionellosis?
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Culture
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How do you culture Legionella?
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On selective (buffered charcoal yeast extract) agar medium that has been supplemented with cysteine and iron
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How long do you expect to Legionella to be cultured?
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3-7 days
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What is the natural reservoir for Legionella?
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freshwater amebae
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What are the primary sources of infection for legionella?
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Environement i.e showers, AC units, cooling towers, whirlpools
Aerosoling equipment i.e. nebulizers, humidifers Aspiration from contaminated water |
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Legionella transmitted from person to person?
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no
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Why does smoking increase the risk of Legionella infection
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Any process that compromises mucociliary clearance as Legionella organisms are cleared from the upper respiratory tract
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How does Legionella adhere to respiratory epithelium?
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Flagellated organisms penetrate the mucus layer in the lower respiratory epithelium and adhere to the target cell surface via specific pili and an outer membrane protein binds C3, favoring opsonization
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Why does legionella have an outer membrane protein binds C3 FAVORING opsonization?
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It is a strictly intracellular bacteria that is internalized via phagocytosis
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How does Legionella survive in a phagosome?
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It has specific gene products that prevent phagosome-lysosome fusion ( delayed organelle trafficking) products prevent phagosome-lysosome fusion in macrophages, whereas other bacterial virulence genes prevent acidification of the phagosome.
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What is the primary host defense mechanism against Legionella infection?
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Cell-mediated immunity
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What is the causative agent in Pontiac fever?
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Pontiac fever is caused by Legionella
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When is onset of illness with Pontiac fever vs. Legionella infection?
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Pontiac fever starts within a few hours of exposure to two days
Legionnaires's disease starts 2 to 10 days after exposure |
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What is the causative agent for the lung damage in Legionella infection?
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It is the cytokines and other reactive mediators from PMNs and T cells that inflict the lung tissue damage
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What are the drugs of choice for Legionella disease?
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A macrolide or a newer quinolone or doxycycline
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What is the typical chest xray for Legionella?
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patchy, diffuse infiltrates
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What electrolyte disturbances are commonly seen with Legionnaires' disease?
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hyponatremia and hypophosphatemia
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What is the genetic makeup of the Influenza virus?
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It has a single-stranded RNA genome with 8-segmented pieces coding for 10 proteins; RNA has negative polarity
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What does Influenza virus look like?
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It has helical nucleocapsid symmetry, with an outer membrane envelope covered with two different types of spikes, hemagglutinin and neuraminidase
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What is the function of hemagglutinin?
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Hemagglutinin is an attachment protein
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What is the function of neuraminidase?
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Neuraminidase acts to sever the virus as it buds from plasma membrane or from mucus
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What are the current human types of influenza?
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the current human types are A (H1N1) and A(H3N3)
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How many different influenza types are there?
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Three
A B C |
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What determines the different influenza types?
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The influenza virus types A, B, C are based on antigenic characteristics of the nucleoprotein and matrix protein antigens.
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What leads to antigenic shift on the influenza virus?
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There is a genetic reassortment that results in a complete change in the configuration of a specific epitope on the surface of the influenza virion
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What leads to antigenic drift on the influenza virus?
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There is a point mutation that results in change in the configuration of a specific epitope on the surface of influenza virion
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What is responsible for the generation of new strains in the influenza virus?
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Antigenic shift
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What is responsible for the random mutations in the influenza virus?
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Antigenic drift
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What influenza types are responsible for epidemic disease?
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Influenza virus types A and B
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What influenza type is responsible for sporadic disease?
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Influenza virus type C
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What is the incubation of influenza?
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The incubation period ranges from 18 to 72 hours
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Where does influenza viral pneumonia primarily affect in the lung?
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It is interstitial in location, with diffuse patchy inflammation localized to interstitial areas at alveolar walls
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What is the effects of influenza infection of the lower respiratory tract?
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Infection of the lower respiratory tract causes severe desquamation of bronchial or alveolar epithelium to the level of the basement membrane
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Why does influenza predispose hosts to secondary bacterial pnuemonia?
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It causes necrosis of the superficial layers of the respiratory epithelium that causes loss of primary host defense .
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What type of influenza is associated with Reye syndrome?
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Influenza B
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What is Reye syndrome?
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It is a rare, often fatal childhood hepatoencephalopathy that is associated with salicylate use
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What drugs should we consider in a patient with an infection of influenza A?
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If it is within 48 hours then amantadine or rimantadine can be given for 3 to 5 days
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What is the mechanism of action of zanamivir?
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It is a neuraminidase inhibitor that has activity against both influenza A and B
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How is yearly flu immunization given?
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With Killed virus vaccine
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How does the influenza virus attach to the host?
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Each virus particle has approximately 500 spikes that bind to sialic acid receptors on host ciliated epithelial cells
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How does neuraminidase help influenza in infection?
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Neuraminidase degrades the protective layer of mucus , allowing the virus to gain access to the cells of the upper and lower respiratory tract
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Where does influenza replication take place?
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The virus replicates in mucus-secretings ciliated cells and in other epithelial cells, resulting cell dysfunction and degeneration
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What is responsible for the systemic symptoms of influenza?
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Cytokines liberated from damaged infiltrating leukocytes
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What is the genetic makeup of respiratory syncytial virus?
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It is an enveloped virus with a negative sense, single-stranded RNA
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What does RSV look like?
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The genome is contained by a helical nucleocapsid surrounded by a lipid envelope.
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What are the components of the RSV lipid envelope?
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RSV has large envelope glycoproteins which consist of a fusion protein (F) and a second glycoprotein (G)
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What are the two antigenic types of RSV?
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the types are A and B; its antigenic differences are in its surface glycoproteins
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How does the hospital control the nosocomial transmission of RSV ?
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By contact isolation and hand washing
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How does RSV cause large multinucleated syncytium to develop?
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The replication of RSV leads to fusion of neighboring cells
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When is the peak activity for RSV infections?
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January or February
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What is the most frequently affected age group of RSV infections?
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infants 2 to 6 months of age
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What is the incubation period of RSV?
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2 to 8 days
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______ is a result of inflammation of the terminal bronchioles, necrosis, and sloughing of the epithelial cells lining the bronchioles
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Bronchiolitis
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What form does the mycobacteria have lipid in its cell wall?
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In the form of long chain fatty acids called mycolic acids.
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What is the doubling time for M. tuberculosis?
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18 hours
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Describe the pattern of growth with virulent strains of M. tuberucolosis?
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Parallel and serpentine patterns
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Why do virulent strains of M. Tuberculosis grow in parallel and serpentine patterns?
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Due to the presence of cord factor, 6,6' trehalose - dimycolate
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What surface macromolecules are responsible for the enhanced virulence of mycobacteria?
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Phenolic glycolipids i.e lipoarabinomannan (LAM)
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What is the major mode of contagion for TB?
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Exposure to airborne organisms from a symptomatic patient
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Mycobacteria are _____ aerobes
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obligate
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Why do mycobacteria prefer the upper lobe of the lung?
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They are obigate aerobes that cause disease only in higly oxygenated tissues
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Mycobacteria is a ______ intracellular bacteria
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facultative
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How does mycobacteria trigger phagocytosis by macrophages?
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M. tuberculosis expresses a cell-wall C3 convertase activity, forming C3b on its surface that is recognized by the macrophage complement receptor CR4, triggering phagocytosis
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What serves as the receptor for mycobacterial LAM?
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It is recognized by the macrophage mannose receptor
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How does M. tuberculosis survive in the macrophage phagosome?
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M. tuberculosis evades phagocytic killing by inhibiting phagolysosome fusion; this is mediated by a tryptophan-asparate-containing coat protein that remains attached to the bacteria
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Mycobacterial glycolipid antigens on MHC II molecules trigger a ____ immune response
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slow
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How does the cord factor act as a virulence factor?
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Cord factor is toxic to PMNs causing irreversible structural and functional damage to mitochondria.
It also stimulates the formation of granulomas |
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What are granulomas?
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Granulomas are collections of macrophages that have taken on properties of epithelial cells (now called epitheliod cells).
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What are giant cells?
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Epitheliod cells that have coalesced within the granuloma to make giant cells
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What is the contribution of CD+4 T cells in TB infection?
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The main contribution of CD+4 T cell comes from the TH1 subset, which releases IFN gamma to stimulate macrophage activation
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The majority of TB infections are ____
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latent
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What is a tubercle?
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A chronic granuloma encapsulated with fibrin that consists of a central area of large, multinucleated giant cells containing tubercle bacilli, a midzone of epitheliod cells, and a peripheral zone of fibroblasts, lymphocytes and monocytes.
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How are TB granulomas visualized on chest X-ray?
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TB granulomas may be visualized by chest xray as lobar (Ghon focus) and perihilar lymph node involvement
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What is a positive PPD test in an HIV test?
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HIV patients with reactions >5 mm are considered positive.
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What are the key TH1 cytokines for controlling TB?
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IL-12, gamma-interferon, TNF
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How does TH1 kill M. tuberculosis?
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The key TH1 effector molecule, required for efficient killing of M. tuberculosis, is nitric oxide, which is produced by the inducible nitric oxide synthase of macrophages
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What is a positive TB skin test in an immunocompetent person?
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Reddening and thickening of the skin of over 15 mm in 48 to 72 hours
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In a latent TB infection, bacterial replication ______ killing, so the bacterial burden is at a ______ level.
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equals
constant |
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The decline of what type of immunity leads to reactivation to TB infection?
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Cell-mediated
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What changes to the lung occurs in reactivation of TB?
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The material within the granulomas becomes caseous. The central of the enlarging granulomas undergoes necrosis, which may break into a bronchus, discharging M. tuberculosis into exhaled air
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What is the empirical therapy of TB?
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INH
Rifampin Pyrazinamide Ethambutol |
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What is the usual treatment for Multi-drug resistant TB?
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usually four or five drugs including Cipro, Amikacin, Ethionamide, and cycloserine
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Who is at the greatest risk for developing hepatic toxicity by INH
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Older patients (> 50)
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Where does tuberculous meningitis usually involve?
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The basilar meninges
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What is a typical complication of tuberculous meningitis?
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Obstructive hydrocephalus and cranial nerve palsies
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If left untreated, what is the progression of reactivation TB?
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Miliary tuberculosis
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What is Potts disease?
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Tuberculosis of the thoracic vertebral bodies.
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Why does BCG vaccination not have any role in the US?
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Due to the low prevalence of the disease
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What is the role of the BCG vaccine?
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It protects against meningitis
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Why should children by vaccinated in superendemic areas with BCG>
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Children cannont be treated with INH
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