Question

A Salmonella type isolate tested Vi antiserum positive and O antiserum negative. What should be done next?

A) Confirm the diagnosis
B) Perform an O agglutination test
C) Repeat the Vi agglutination test
D) Conduct a PCR analysis

Answer 1

The appropriate next step after an isolate tested Vi antiserum positive and O antiserum negative is to confirm the diagnosis, preferably using PCR analysis for accurate identification of Salmonella species.

Step-by-step explanation:

If an isolate tested Vi antiserum positive and O antiserum negative, the next step would be to confirm the diagnosis. The Widal test, which measures agglutination in the presence of such antisera, can produce false positives and negatives, thus additional testing is recommended for a definitive diagnosis. In this context, performing an O agglutination test may not be sufficient as it might still yield inaccurate results. A more reliable method such as PCR analysis could be more conclusive for the identification of Salmonella species. PCR is able to detect the presence of specific genetic material and is not affected by the same limitations as the Widal test.