dog bite

Dilworth bactitech at
Tue Mar 20 21:38:15 EST 2001

Pasteurella multocida is also indole positive, and is one of the few
gram negatives sensitive to Penicillin.  Its morphology on gram stain is
a coccobacillus, like Derek said, very short.  The smell is very typical
on blood agar, and once you smell it, you'll recognize it again.  The
odor, oxidase +/indole + and no growth on MacConkey pretty much nails
it, except for formal identification.  We use Vitek automated systems,
which will identify it.  One must perform Kirby Bauer susceptibility
testing, as Vitek is unable to perform the sensitivity.

Judy Dilworth, M.T. (ASCP)

Derek Law wrote:
>  This is probably Pasteurella multocida, a small gram negative rod, which
> stains poorly with the counterstain and may show bipolar staining. It grows
> aerobically on various rich media such as tryptone soya agar or blood agar.
> Colonies are convex, grey in colour with a strong smell of indole. The
> colonies look very much like E. coli but are positive in an oxidase test (E.
> coli is negative). It won't grow on media containing bile salts such as
> MacConkey agar.
> Pasteurella is the most common cause of wound infection  caused by animal
> bites. The organism is normally susceptible to many antibiotics including
> penicillin/ ampicillin.
> Derek Law

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