How many known Salmonella serotypes exist, and how many are detected in the USA?

• A. Approximately 2,600 known serotypes exist; about 100 are detected in the USA.
• B. Approximately 1,000 known serotypes exist; about 50 are detected in the USA.
• C. Approximately 5,000 known serotypes exist; about 2,000 are detected in the USA.
• D. Approximately 2,600 known serotypes exist; about 2,000 are detected in the USA.

Answer: (A)

Salmonella enterica has thousands of distinct serovars identified by differences in its surface antigens, and the number of known serotypes worldwide is around 2,600. In the United States, only a small subset of these serovars has been detected through surveillance and clinical reporting—roughly about a hundred. So the statement that there are about 2,600 known serotypes globally and about 100 detected in the USA best matches the real balance between global diversity and local surveillance. The other options imply far more serovars present in the U.S. than is typically observed or misstate the global-to-local ratio, which isn’t consistent with surveillance data.