Microbiology - Bacterial Pneumonia I and II Flashcards
What are the unique presentations of Pseudomonas aeruginosa in special populations?
P. aeruginosa has a few community-acquired presentations: endocarditis in IV drug addicts,
Otitis externa in underchlorinated hot tubs,
Osteochondritis in sneaker punctures,
corneal infections under contact lenses
How is infection (pneumonia) with a pseudomonad treated?
Treat with latest combinations of antibiotics, test Ab sensitivity both before and during treatment.
All, but particularly P. aeruginosa, have extreme antibiotic resistance from combination of low-permeability outer membrane and efflux pumps.
How is infection (pneumonia) with pseudomonas diagnosed?
Diagnose by culture and Gram stain
Where is pseudomonas aeruginosa infection most commonly found?
Hospitals
All pseudomonas infections can present as septicemia/pneumonia with poor prognosis.
P. aeruginosa and B. cepacia have minimal growth requirements ➔ contaminate hospital sol’ns
Where is B. cepacia (pseudomonas) most commonly found?
CF centers
All can present as septicemia/pneumonia with poor prognosis.
In what populations is B. pseudomallei (pseudomonas) most commonly found?
B. pseudomallei in previously-ill travelers/immigrants or Vietnam veterans
All can present as septicemia/pneumonia with poor prognosis.
In what population is B. mallei most commonly found?
B. mallei in previously-ill travelers/immigrants with animal handling history.
All can present as septicemia/pneumonia with poor prognosis.
What are the pseudomonas pathogens?
Four P/B pathogens:
P. aeruginosa a common&serious nosocomial pathogen;
B. cepacia common, serious in context of CF;
B. pseudomallei and B. mallei rare in US but can be lethal
How is P. aeruginosa unique when growing it in culture?
P. aeruginosa produces green pyocyanin in culture.
Are the pseudomonads gram + or -?
All Gram(-), strict aerobes, nonfermenters, Oxidase(+), grow easily in culture.
What is the treatment for chlamydial pneumonia?
Treat with tetracyclines (doxycycline) EXCEPT for pregnant/pediatric/allergic patients, who get erythromycin or other alternatives. Patients who get alternatives may need follow-up testing and retreatment.
What are the unique factoids about chlamydia?
Chlamydia is a small, obligate intracellular bacterium (so must use drugs that penetrate the human cell membrane).
How does chlamydia replicate?
Chlamydia replicate in a unique manner beginning with tiny, infectious, rugged, elementary bodies which “unpack” into reticulate bodies after infection.
Reticulate bodies form intracellular inclusions that are visible on microscopy; within the inclusions they multiply by binary fission, forming new reticulate bodies and later new elementary bodies.
What special virulence factor does chlamydia have?
Unusual life cycle complicates research; one known virulence factor is T3SS used for entry & establishing inclusion body.
What kind of chlamydia causes the urogenital infection?
C. trachomatis is the cause of several human diseases, particularly the common urogenital infection (safe sex practices!)
C. pneumoniae, C. psittaci, and C. trachomatis can all cause _______
These are the chlamydias that cause pneumonia.
What is problematic about P. aeruginosa as a nosocomial infection?
A Extreme antibiotic resistance
B Propensity to grow in low-nutrient aqueous solutions
C Ability to cause bacteremia
D All of the above
1: D: P aeruginosa is a formidable opponent for your hospital infection control
What is SIMILAR about B. cepacia and B. pseudomallei?
Normally freeliving water microbes
- To which patient(s) is a B. cepacia infection dangerous despite treatment?
A A pediatric CF patient
B A geriatric cancer patient
C A previously-healthy woman undergoing urinary catheterization
D A and B not C
E All of the Above
2: A: Cystic Fibrosis is the most important predisposition for poor outcomes of cepacia infection.
Why has Legionella only recently emerged as a human pathogen?
Humans have created a new, human-proximal, habitat for it
All these patients have Legionella infections – which is at highest risk for a bad outcome?
22yr old previously-healthy female with a fever
55yr old previously-healthy female with pneumonia
77yr old smoker male with pneumonia
77yr old smoker male with pneumonia
Mycoplasma pneumonia resolves: Spontaneously With antibiotic treatment With antitoxin treatment With antiviral treatment
Spontaneously; and
With antibiotic treatment
What kind of bacteria is legionella?
Gram (-) rod;
Free-living form is motile (flagella); intracellular form is non-motile;
Opportunistic facultative intracellular pathogen with variable infection outcome
How do you trace a legionella outbreak?
LD outbreaks trace to contaminated locations (NOT people)
T/F: LD pneumonia is life-threatening even when treated with antibiotics
True
How is legionella diagnosed?
Optimal diagnosis is by BOTH urine antigen test and culture of respiratory secretions (fastidious, special media required)
For geriatric community-acquired pneumonias in general, take samples for culture/ELISA first, start treatment w/ levofloxacin second, get labs back third
How does legionella survive endocytosis?
Legionella survives endocytosis by monocytes¯ophages by altering endosomes so that it can multiply in them and then escape
Is legionella contagious?
Exposure is from aspiration or inhalation of contaminated water - NOT contagious
How is infection with C. burnetti diagnosed?
Diagnose by immunohistochemistry
What bacteria causes Q fever?
C. burnetti
What kind of bacteria is C. burnetti?
C. burnetii is a small coccus to short rod, zoonotic infection from ruminants.
How is C. Burnetti transmitted?
Transmitted by aerosols, grows in aveolar monocyte/macrophages, survives endolysosomal fusion, extremely infectious, long-lived in environment,
What is the presentation of infection with C. burnetti?
causes pneumonia+hepatitis = Q Fever
How is Q fever (Infection with C. burnetti) treated?
treat with tetracyclines or fluoroquinolones
What CBC finding does mycoplasma pneumonia cause?
Immunopathology: antibodies against mycoplasma cross-react with red blood cells (cold agglutinins) → anemia during infection.
How are Mycoplasma structurally unique?
Mycoplasma are unique among bacteria in lacking a cell wall and including cholesterol in their cell membrane.
What is the most common infection caused by mycoplasma?
Causes “walking” pneumonia: mild and self-limited
What virulence factor does mycoplasma use to exacerbate the cough it causes?
CARDS exotoxin-induced ciliostasis, local inflammation, local tissue destruction.
Ciliostasis → dry cough, exacerbates bronchitis, asthma
How is pneumonia caused by mycoplasma treated?
Treat as needed with tetracyclines or macrolides (fluoroquinolones also fine)
How does mycoplasma survive initial immune response to cause pneumonia?
Persistence through slow growth and intracellular hiding
