A specimen was collected from a deep wound.A smear was prepared and Gram stained and samples were inoculated onto two blood agar plates.Both blood agar plates were incubated for 48 hours at 35°C, but one blood agar plate was incubated aerobically and the other was incubated in an anaerobe jar.The Gram stain of the original specimen showed large gram-positive bacilli.After incubation, there was no growth on the blood agar plate that was incubated aerobically, but the plate incubated in the anaerobe jar grew beta hemolytic colonies.A Gram stain of these colonies showed large gram positive bacilli, some with unstained inclusions, suggestive of endospores.What is the most likely genus of bacteria observed?

Question

Quizplus · Accepted Answer

The presence of large gram-positive bacilli with endospores and beta hemolytic colonies on anaerobic incubation suggest the genus Clostridium. Bacillus also produces endospores, but it typically does not grow well under anaerobic conditions. Mycobacterium and Listeria are both gram-positive, but they do not form endospores and are not typically observed as large bacilli. Corynebacterium is also a gram-positive rod, but it does not form endospores and is typically not associated with beta hemolysis.

A Specimen Was Collected from a Deep Wound