Harr Microbiology Practice Test 2026 – 400 Free Practice Questions to Pass the Exam

The correct choice identifies the genera Escherichia, Salmonella, Shigella, and Yersinia, which are well-documented enteric pathogens responsible for causing diarrhea across various populations.

Escherichia coli, particularly specific pathogenic strains such as enterotoxigenic, enteropathogenic, and enterohemorrhagic E. coli, are major contributors to gastrointestinal illnesses. They often result in significant outbreaks and can cause symptoms ranging from mild diarrhea to severe dysentery.

Salmonella species are notorious for their role in foodborne illnesses, leading to salmonellosis characterized by diarrhea, fever, and abdominal cramps. Transmission typically occurs through contaminated food or water, and these pathogens can also lead to severe systemic infections.

Shigella is known for causing bacillary dysentery (shigellosis), where the bacteria invade the intestinal lining, leading to inflammation and severe diarrhea, sometimes with blood and mucus.

Yersinia enterocolitica can cause gastroenteritis, particularly within certain populations, including children. It is often associated with the consumption of contaminated food, especially undercooked pork.

The other options include genera that, while they may have clinical relevance, are not primarily associated with causing diarrhea in the same way