Microbiology – MCQ 69 – Pustule with McFadyean positive bacilli

A man, after skinning a dead animal, developed a pustule on his hand. A smear prepared from the lesion showed the presence of Gram positive bacilli in long chains which were positive for McFadyean’s reaction. The most likely aetiological agent is :
A. Clostridium tetani
B. Listeria monocytogenes
C. Bacillus anthracis
D. Actinamyces sp

Correct answer : C. Bacillus anthracis

The history (animal contact), clinical picture (pustule in the area of contact) and lab findings (gram positive bacilli in chains with McFadyean reaction positive) are all characteristic of infection by Bacillus anthracis.