Pneumonia Part 1 Flashcards
Four P/B pathogens:
- P aeruginosa a common and serious nosocomial pathogen (grows in water, vulnerable patients, Ab resistance, VAG)
- B cepacia common, serious in context of CF
- B pseudomallei and B mallei are rare in US but can be LETHAL (untreated pseudomallei can be fatal in 7-10 days; milder infections could resolve and reactivate yrs later); latter two are reportable
All the P/B pathogens are
gram negative, strict aerobes, nonfermenters, oxidase +, grow easily in culture; P aeruginosa makes green pyocyanin (its exotoxin) in culture;
usually FREE-LIVING ENVIRONMENTAL
Songg
All, but particularly P aeruginosa, have
extreme antibiotic resistance from combination of low-perm outer membrane and efflux pumps
P aeruginosa and B capacia have
minimal growth requirements and can contaminate hospital solutions;
(tougher for B capacia to infect otherwise-healthy patients; can lead to outbreaks with cepacia pneumonia in CF centers; NO PYOCYANIN)
P aeruginosa has a few
community-acquired presentations: enducoarditis in IV drug addicts, otitis externa/folliculitis in underchlorinated hot tubs, osteochondritis in sneaker punctures, corneal infections under contact lenses (COOE);
burns, CF, long-term catheterization, immunosuppression;
also has T3SS (exotoxin) and endotoxin that can lead to sepsis; also glycocalyx that’s ANTIPHAGOCTYIC
Most common presentations for serious disease with pseudomonas:
- P aeruginosa in hospitals (CF pneumonia, burns, nosocomia UTI; ecthyma gangrenosum)
- B cepacia in CF centers
- B pseudomallei in previously-ill travelers/immigrants or Vietnam vets (melioidosis; contaminated water, soil); also IV drug users
- B. mallei in previously-ill travelers/immigrants with animal handling history (rare zoonosis; unlikely human-to-human transmission);
ALL can present as septicemia/pneumonia with poor prognosis
Diagnose pseudomonas by
culture and gram stain;
Aeruginosa culture will fail if anaerobic; metallic sheen on triple-sugar-iron agar, green color on nutrient agar (pyocyanin);
for pseudomallei and mallei, think PATIENT HISTORY
Treat pseudomonas with
latest combo of antibiotics, test Ab sens both before AND during treatment
(for aeruginosa, remove/change catheters/IVs)
Chlamydia is a
small obligate IC bacterium (need drugs that can penetrate human cell membrane)
Chlamydia replicate in a
unique manner, beginning with tiny, infectious, rugged elementary bodies which unpack into reticulate bodies after infection
RB’s form
IC inclusions that are visible on microscopy: within the inclusions they multiply by binary fission, forming new RB’s and later new EB’s
Unusual life style
complicates research; one known virulence factor is T3SS used for entry and establishing inclusion body
C trachomatis is the
cause of several human diseases, particularly the common urogenital infection (SAFE SEX PRACTICE)
What three guys can cause pneumonia?
C pneumoniae (retirement communities, adult comm-acquired pneumonia), C psittaci (infected birds like parrots), C trachomatis (birth canal: conjunctivitis and pneumonia)
Treatment of chlamydia can often be
initiated on physical findings, additional diagnostics are available and may be desired in various situations (tissue culture for C trachomatis in rape victims, serology or MIF to differentiate pneumonias);
C psittaci shows consolidation in single lower lobe
