Question

A 48-year-old man presents to the emergency department with 2 days of crampy abdominal pain, nausea, vomiting, diarrhea, and fever. He has not had any blood in his stool. He denies contact with anyone with similar symptoms recently. He has not eaten any raw or unprocessed foods recently. The only food that he did not prepare himself in the past week was a breakfast of eggs “sunny side up” and bacon that he had at a diner the day before his symptoms started. On examination, he is tired appearing; his temperature is 37.7°C. The physician interprets a positive “tilt test,” indicating significant volume depletion. His abdominal examination is notable for diffuse tenderness. A MacConkey agar plate culture results in the biochemical reactions as follows: TSI K/A with H2S, citrate positive, and urea negative. The serological test were positive for this pathogen.

1. On the basis of the biochemical reactions, which organism do you think this is?

2. What are the most common sources of human infections with this organism?

Answer 1

Answer: According to the biochemical reaction, the organism is gram negative bacilli (Escherichia coli). As with the TSI K/A with H2S it gives positive for citrate.

The most common source of human infection with E. Coli bacteria is through the consumption of uncooked meat, raw milk or contaminated foods.