The three genera most frequently documented as causative agents of human bacterial origin foodborne illness in the US are?

• A. Streptococcus, Bacillus and Salmonella
• B. Salmonella, Staphylococcus and Streptococcus
• C. Staphylococcus, Campylobacter and Salmonella
• D. Shigella, Salmonella and Staphylococcus

Answer: (C)

The main idea is that the most frequently documented bacterial causes of human foodborne illness in the US come from organisms that affect foods in different ways and from common contamination sources. Staphylococcus aureus is a top culprit because it can produce heat-stable toxins in foods that are improperly stored or handled, leading to rapid onset vomiting and nausea even if the food is later cooked. This makes it a common problem in foods that require hand preparation or sit out at room temperature, such as salads, pastries, and dairy-containing items.

Campylobacter is a leading cause of bacterial gastroenteritis and is strongly associated with undercooked poultry and raw milk. It causes painful diarrhea and abdominal cramps, and its prevalence in widely consumed foods helps explain its prominence.

Salmonella is widespread across many foods—poultry, eggs, beef, dairy, and even produce—making it a frequent cause of infectious gastroenteritis after ingestion of live bacteria.

Together, these three genera account for a large share of documented bacterial foodborne illness in the US because they cover toxin-mediated illness from improper storage, and infectious illness from common animal-source and produce-associated contamination.