Question

A 24 years old cook in a hostel mess suffered from enteric fever 2 years back. The chronic carrier state in this patient can be diagnosed by:

• A. Vi agglutination test
• B. Blood culture in Brain Heart Infusion broth
• C. Widal test
• D. C-Reactive protein

Hint:

Chronic typhoid carriers keep shedding Vi antigen, so Vi antibody stays high long after the fever is gone.

Answer 1

The Correct Option is A

Step 1: Understand what a chronic carrier is.
Some people who recover from typhoid (enteric) fever keep carrying Salmonella typhi in their gallbladder for a year or more without being sick themselves. They can still spread the bacteria to others through food they handle, which is exactly the concern with a cook.

Step 2: Recall the antigen that marks a carrier.
Salmonella typhi has a capsular antigen called the Vi (virulence) antigen on its outer surface. In a chronic carrier, the bacteria keep releasing this antigen into the body over months, so the person's blood keeps making antibody against it, even though the acute illness is long over.

Step 3: Explain why the Vi agglutination test works here.
The Vi agglutination test looks for this antibody in the blood. A high or rising Vi antibody titer, especially without a recent illness, points strongly to ongoing carriage of the bacteria, most often in the gallbladder. This makes it a useful screening tool for finding carriers, particularly among food handlers.

Step 4: Rule out the other tests.

(2) Blood culture in Brain Heart Infusion broth: Blood culture is most useful in the first week of acute fever, when bacteria circulate in the blood, chronic carriers usually do not have positive blood cultures since the bacteria sit in the gallbladder or intestine, not the bloodstream.

(3) Widal test: This detects O and H antibodies made during active infection, and these antibody levels fall over time, so they are not reliable markers of chronic carriage two years after the illness.

(4) C-Reactive protein: A general marker of inflammation, raised in many illnesses, it tells nothing about typhoid carriage specifically.

Final Answer:
The Vi agglutination test is the right tool to pick up a chronic typhoid carrier.
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