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Microbiology ` microbiology—cliNical bacteriology Microbiology ` microbiology—cliNical bacteriology SEcTioN ii 143

Bordetella pertussis Gram ⊝, aerobic coccobacillus. Virulence factors include pertussis toxin (disables G i ), adenylate
cyclase toxin ( cAMP), and tracheal cytotoxin. Three clinical stages:
ƒ Catarrhal—low-grade fevers, Coryza.
ƒ Paroxysmal—paroxysms of intense cough followed by inspiratory “whooP” (“whooping cough”),
posttussive vomiting.
ƒ Convalescent—gradual recovery of chronic cough.
Prevented by Tdap, DTaP vaccines. May be mistaken as viral infection due to lymphocytic
infiltrate resulting from immune response.
Treatment: macrolides; if allergic use TMP-SMX.

Brucella Gram ⊝, aerobic coccobacillus. Transmitted via ingestion of contaminated animal products (eg,
unpasteurized milk). Survives in macrophages in the reticuloendothelial system. Can form non-
caseating granulomas. Typically presents with undulant fever, night sweats, and arthralgia.
Treatment: doxycycline + rifampin or streptomycin.

Legionella Gram ⊝ rod. Gram stains poorly—use silver Think of a French legionnaire (soldier) with
pneumophila stain. Grow on charcoal yeast extract his silver helmet, sitting around a campfire
A medium with iron and cysteine. Detected by (charcoal) with his iron dagger—he is no sissy
presence of antigen in urine. Labs may show (cysteine).
hyponatremia. Legionnaires’ disease—severe pneumonia
Aerosol transmission from environmental (often unilateral and lobar A ), fever, GI and
water source habitat (eg, air conditioning CNS symptoms. Common in smokers and in
systems, hot water tanks). No person-to-person chronic lung disease.
transmission. Pontiac fever—mild flu-like syndrome.
Treatment: macrolide or quinolone.

Pseudomonas Aeruginosa—aerobic; motile, catalase ⊕, Corneal ulcers/keratitis in contact lens wearers/
aeruginosa gram ⊝ rod. Non-lactose fermenting. minor eye trauma.

A Oxidase ⊕. Frequently found in water. Has a Ecthyma gangrenosum—rapidly progressive,
grape-like odor. necrotic cutaneous lesion B caused by
PSEUDOMONAS is associated with: Pseudomonas bacteremia. Typically seen in
Pneumonia, Sepsis, Ecthyma gangrenosum, immunocompromised patients.
UTIs, Diabetes, Osteomyelitis, Mucoid Treatments include “CAMPFIRE” drugs:
polysaccharide capsule, Otitis externa ƒ Carbapenems
(swimmer’s ear), Nosocomial infections (eg, ƒ Aminoglycosides
catheters, equipment), Addicts (drug abusers), ƒ Monobactams
B Skin infections (eg, hot tub folliculitis, wound ƒ Polymyxins (eg, polymyxin B, colistin)
infection in burn victims). ƒ Fluoroquinolones (eg, ciprofloxacin,
Mucoid polysaccharide capsule may contribute levofloxacin)
to chronic pneumonia in cystic fibrosis ƒ ThIRd- and fourth-generation
patients due to biofilm formation. cephalosporins (eg, ceftazidime, cefepime)
Produces PEEP: Phospholipase C (degrades ƒ Extended-spectrum penicillins (eg,
cell membranes); Endotoxin (fever, shock); piperacillin, ticarcillin)
Exotoxin A (inactivates EF-2); Pigments:
pyoverdine and pyocyanin (blue-green
pigment A ; also generates reactive oxygen
species).

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