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.