Aerobic Non–Spore-Forming
Gram-Positive Rods
Clinical Microbiology Review 171
ORGANISM PATHOGENICITY GRAM STAIN CULTURE KEY CHARACTERISTICS OTHER
Corynebacteriumspp
Corynebacterium
diphtheriae
Called diphtheroids
because resemble
C. diphtheriae.ID requires
demonstration of
toxin production.
Modified Elek
immunoprecipita-
tion test. PCR for
TOXgene.Facultative anaer-
obes. Grow on
most media.Gray-black
colonies with
brown halos on
Tindale agar.
Black colonies on
cystine tellurite.
Loeffler medium
stimulates growth
& production of
metachromatic
granules.Normal on skin &
mucous membranes.
Opportunistic
pathogens.Diphtheria. Rare in
U.S.Irregular, slightly
curved, nonparallel
sides, club-shaped
ends. Chinese letter
or picket fence for-
mation (palisades).Same as above.Catalase pos. Nonmotile.Catalase pos. Nonmotile.
Toxin producing.continued...