GPBs

Question 1

What would you look for if you have boxy gram positive bacilli that are spore forming, what are the main possibilities and how to diff?

Answer 1

Bacillus: check B-hemolysis and motility. If positive, can be non-anthrax bacillus such as B. cereus and B. subtilis or one of many others; If negative, think B. anthracis.

Question 2

If your GPB are not spore-forming and don’t otherwise appear to be Bacillus genus, what morphology on gram stain would you look for?

Answer 2

branching or non-branching

Question 3

If you have branching beaded GPB what are you thinking you may have?

Answer 3

Nocardia or Actinomyces: the former is found in soil and causes invasive pulmonary and disseminated infections esp in immcomped; Latter is in mout/colon.vag and introduces to other areas by trauma such as IUD or tooth extraction, causing draining abscesses w/ sulfur grans

Question 4

describe Listeria in terms of appearance on gram stain and major biochem characteristics to ID

Answer 4

a gram positive bacilli, no branching, catalase positive, motility and bile esculin positive

Question 5

If you had a GPB that was catalase positive what would diff between it being Listeria and Corynebacterium, biochemically?

Answer 5

Corynebacterium is non-motile and bile esculin negative as well as having it’s characteristic shapes and arrangements