Quick Review Cards for Medical Laboratory Science

Miscellaneous Gram-Negative Rodscontinued Clinical Microbiology Review 197

ORGANISM PATHOGENICITY GRAM STAIN CULTURE KEY CHARACTERISTICS

Gardnerella

Legionella

Pasteurella

multocida

TM = Thayer-Martin; BCYE = buffered charcoal yeast extract.

Catalase & oxidase neg.

Tests for Dx of BV: clue cells

(vaginal epithelial cells

covered with gram-variable

rods), whiff test (10% KOH

added to vaginal secretion

Æ fish-like odor).

Oxidase pos. ID by immuno-

fluorescent stain. Serology.

Oxidase, catalase, &

indole pos.

Normal flora of female

genital tract. Associated

with bacterial vaginosis (BV)

when it & anaerobic GNR are

predominant & Lactobacillus

is absent. Linked to maternal

& neonatal infections, bac-

teremia, rarely UTI

Legionnaire’s disease, Pontiac

fever. Found in water (e.g., air

conditioners, showerheads,

whirlpools). Contracted by

inhalation of aerosol

Contracted by bite or scratch

of cat or dog or contact with

infected carcass. Wound &

respiratory tract infection

Small, pleomorphic

gram-variable rods

Small, pleomorphic,

weakly staining GNR

Pleomorphic GNCB

with bipolar staining

Not recommended for Dx of

BV. Grows on SBA, PEA, CNA,

human blood Tween (HBT)

agar, V agar. Produces diffuse

beta hemolysis only on media

containing human blood.

Requires ↑CO 2 & 48–72 hr

incubation.

Grows on BCYE in 3–4 days.

Pale yellow-green fluores-

cence with Wood’s lamp.

Grows on SBA & CHOC, but not

MAC. Musty odor.