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Micro - pneumonias


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What are 6 agents of community-acquired pneumonia?
1.Strep pneumoniae
3.H. influenzae
4.Mycoplasma pneumoniae
5.S. aureus
6.Chlamydia pneumoniae
How does Pseudomonas stain? Where is it found in the environment?
*G- rod
*ubiquitous in environment
What agent is most closely associated with ventilator-associated pneumonia?
What causes the blue-green color often seen with Pseudomonas?
Describe the mucoid morphotype of pseudomonas seen in CF patients. Why is it so hard to eradicate? What causes damage to the lung tissue?
*able to form and grow in a mucoid biofilm which makes it difficult to eradicate
*heavy PMN activity inflicts tissue damage
*cycle of repeated chronic infections
Pseudomonas is generally amenable to treatment with PCN.
False: Pseudomonas has multiple drug resistance issues.
How does H. influenzae stain? What are its culture characteristics? Where can it be found normally?
*G- rod
*will not grow on SBA or MAC due to NAD+ requirements
*normal flora of the URT
Name 3 forms of invasive disease caused by H. influenzae. What serotype is usually responsible for these conditions?
*Type b
The vaccine for H. influenzae is a conjugated protein vaccine. What population is afforded protection as a result of conjugation? Why?
*children under 2 yrs
*they are otherwise unable to generate a T-dependent response against a polysaccharide immunogen
What common childhood condition can be caused by nontypable H. influenzae?
Otitis media
How does Mycoplasma pneumoniae stain?
It does not accept a Gram stain because it lacks a cell wall.
How is M. pneumoniae transmitted? How is the bug able to colonize the epithelia?
*p-p by aerosol secretions
*use a specialized attachment tip to adhere to respiratory cilia
Does M. pneumoniae invade host cells? What is a virulence factor it produces?
*it remains extracellular
*produces cmpds (e.g. H2O2) that inhibit ciliary beating
M. pneumoniae causes walking pneumonia - what are the symptoms of this? In what part of the lungs does it occur?
*cough, fever, low sputum production
*ltd to bronchial mucosa - no lobar or alveolar involvement
Because of its ubiquitous nature, M. pneumoniae can be hard to identify as a pathogen. What is one test that can be used to ID it?
*cold agglutins
Which would be the better treatment for M. pneumoniae - PCN-G or erythromycin? Why?
Erythromycin - the bug lacks a bacterial cell wall, thus B-lactams would be highly ineffective.
How does Bordetella stain? What are its growth characteristics in culture?
*G- rod
*grows only on specialty agar
*yields "mercury colonies"
Which is more contagious - bordatella or legionella?
Bordatella is highly contagious whereas there is no p-p spread for legionella.
What are of the body does bordatella colonize?
Ciliated epithelium of nasopharynx.
What are the 3 stages of infection with bordatella? What are the symptoms of each? How long does each last?
1.Catarrhal: URI symptoms; 1-2 wks
2.Paroxysmal: mucus accumulation, coughing fits; 2 wks
3.Convalescent: decreased coughing; <8 wks
Does bordatella penetrate the host cells? What are some virulence factors it produces?
*colonize mucosal surface and do not penetrate
*pertussis toxin: ADP-ribosylates G-protein to activate adenylate cyclase
*tracheal cytotoxin: destroys cilia and ciliated cells
What causes the "whoop" seen in whooping cough?
Bordatella colonizes the mucosal surface and destroys cilia. Pts are unable to clear respiratory secretions and mucus and this leads to violent paroxysms of coughing followed by a sharp inspiration.
What might be abnormal about the CBC of a pt infected with bordatella?
This infection causes lymphcytosis so a large number of WBC would be expected.
Is Bordatella typically fatal?
No; but it can be for patients with underlying heart or pulmonary conditions.
What type of vaccine is in use for bordatella? Has this always been the case?
*an acellular vaccine of purified protein filtrates is currently in use
*this replaced a whole cell attenuated vaccine removed for publlicity purposes
Where might legionella be found in the environment? How is it acquired?
*aqueous environments
*inhalation of droplets
How is Legionella able to survive in macrophages? Whta kind of immune response is required to clear the infection?
*prevents fusion of phagosome with lysosome and acidification
*T-cell mediated; also TNF-a which inhibits intracellular growth
What are the symptoms of Legionnaire's disease?
*flu-like symptoms develop into pneumonia
*NO cough or sputum
*N/V/D fairly common
*low PO2
What are the symptoms of Pontiac Fever? What treatment is recommended?
A mild flu that is self-ltd. No treatment recommended.
How is infection with Legionella usually diagnosed?
*Culture is difficult
*clinical findings
*urine Ag test

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