Several people from a picnic came down with a gastrointestinal disturbance, and public health officials suspected a case of food poisoning. The food was cultured, and after 24 hours of incubation the hot dogs yielded growth on SBA of small, round, smooth, translucent colonies surrounded by a narrow zone of $\beta$-hemolysis. A Gram stain showed gram-positive coccobacilli. Motility medium was inoculated and an umbrella pattern of motility was observed at room temperature. What organism was isolated as the cause of the illness?

Question

Quizplus · Accepted Answer

The description matches Listeria monocytogenes which is a gram-positive coccobacillus that can cause gastrointestinal disturbances and is commonly found in contaminated food such as hot dogs. It also exhibits beta-hemolysis and motility, which is observed as an umbrella pattern. Rhodococcus equi and Rothia dentocariosa are not known to cause food poisoning, and Corynebacterium diphtheriae is a gram-positive rod, not a coccobacillus.

Several People from a Picnic Came Down with a Gastrointestinal β\betaβ

Several People from a Picnic Came Down with a Gastrointestinal $\beta$