Question:
Which one of the following gives strong evidence of typhoid fever carrier status?
Which one of the following gives strong evidence of typhoid fever carrier status?
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Think about which test ties the isolated organism specifically to chronic gallbladder carriage.
Updated On: Jul 7, 2026
- Isolation of core antigen
- Isolation of Vi antigen
- Persistence of Vi antibodies
- Demonstration of typhoid bacilli in stools
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Question.
A typhoid carrier is a person who keeps shedding Salmonella Typhi, usually from the gallbladder, without being sick. The question asks which finding gives strong, direct proof of this carrier state.
Step 2: Key Concept.
The Vi antigen is a capsule (surface) antigen made mostly by Salmonella Typhi strains that live long-term in the gallbladder and keep escaping the immune system. Finding this antigen on the organism recovered from a carrier is a strong, specific marker tied to true chronic carriage, not just any passing infection.
Step 3: Detailed Explanation.
Core antigen is a term linked to Hepatitis B virus, not Salmonella Typhi, so it has no role here and is simply a distractor.
Isolation of the Vi antigen from the organism recovered from stool, urine, or bile confirms that the strain is the Vi-antigen-bearing type strongly linked with chronic gallbladder carriage, giving firm evidence of true carrier status.
Persistence of Vi antibodies in the blood is only presumptive evidence; a raised antibody titre suggests someone might be a carrier and prompts further testing, but antibodies alone do not prove that bacteria are still being shed right now.
Demonstration of typhoid bacilli in stools shows current shedding, but by itself does not distinguish a short-term convalescent excreter from a long-term chronic carrier unless it is confirmed as the Vi-antigen strain and repeated over months.
Step 4: Final Answer.
Since it directly and specifically ties the organism to chronic carriage, isolation of the Vi antigen is taken as the strongest evidence of carrier status.
A typhoid carrier is a person who keeps shedding Salmonella Typhi, usually from the gallbladder, without being sick. The question asks which finding gives strong, direct proof of this carrier state.
Step 2: Key Concept.
The Vi antigen is a capsule (surface) antigen made mostly by Salmonella Typhi strains that live long-term in the gallbladder and keep escaping the immune system. Finding this antigen on the organism recovered from a carrier is a strong, specific marker tied to true chronic carriage, not just any passing infection.
Step 3: Detailed Explanation.
Core antigen is a term linked to Hepatitis B virus, not Salmonella Typhi, so it has no role here and is simply a distractor.
Isolation of the Vi antigen from the organism recovered from stool, urine, or bile confirms that the strain is the Vi-antigen-bearing type strongly linked with chronic gallbladder carriage, giving firm evidence of true carrier status.
Persistence of Vi antibodies in the blood is only presumptive evidence; a raised antibody titre suggests someone might be a carrier and prompts further testing, but antibodies alone do not prove that bacteria are still being shed right now.
Demonstration of typhoid bacilli in stools shows current shedding, but by itself does not distinguish a short-term convalescent excreter from a long-term chronic carrier unless it is confirmed as the Vi-antigen strain and repeated over months.
Step 4: Final Answer.
Since it directly and specifically ties the organism to chronic carriage, isolation of the Vi antigen is taken as the strongest evidence of carrier status.
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