EI Tor vibrio may be differentiated from classical vibrio by fact that EI Tor vibrio-
**Question:** EI Tor vibrio may be differentiated from classical vibrio by the fact that EI Tor vibrio -
A. lacks the cholera toxin production
B. produces a unique hemagglutination pattern
C. is resistant to tetracycline
D. lacks the Vi antigen on its capsule
**Correct Answer:**
**Core Concept:** EI Tor vibrio is a serogroup of Vibrio cholerae, which is the causative agent of cholera. The differentiation between EI Tor vibrio and classical vibrio can be made based on several characteristics.
**Why the Correct Answer is Right:**
The correct answer is D. EI Tor vibrio lacks the Vi antigen on its capsule. This is a significant characteristic as the Vi antigen is present in classical Vibrio cholerae strains, including those causing classical cholera. The Vi antigen is a polysaccharide capsule, which confers protection against phagocytosis and serves as a serological marker for the classification of Vibrio cholerae strains.
**Why Each Wrong Option is Incorrect:**
A. Lack of cholera toxin production is not a distinguishing feature between EI Tor vibrio and classical vibrio. Both EI Tor and classical strains can produce cholera toxin, which is responsible for the clinical manifestations of cholera.
B. The unique hemagglutination pattern is not a reliable method for distinguishing between EI Tor and classical vibrio strains. Differentiation between these two serogroups should not rely on a single test result as various strains within the same serogroup may exhibit different hemagglutination patterns.
C. Resistance to tetracycline is not specific to EI Tor vibrio. Both EI Tor and classical vibrio strains can exhibit resistance to tetracycline due to antibiotic usage in the environment.
**Clinical Pearl:**
The Vi antigen is crucial in differentiating EI Tor vibrio from classical Vibrio cholerae, as it is absent in EI Tor strains. This enables proper classification and clinical management of cholera cases. It is essential for healthcare professionals to be aware of the Vi antigen's absence in EI Tor strains, which can aid in accurate diagnosis and treatment of cholera cases.