El Tor biotype of Vibrio cholerae O1 produces a milder disease than classical biotype. The molecular reason for milder disease in El Tor is:

• A El Tor produces no cholera toxin
• B El Tor lacks the CTX bacteriophage
• C El Tor is non-motile and cannot colonize the intestine
• D El Tor produces less cholera toxin per unit bacteria and has greater environmental survival, permitting asymptomatic carriage ✓

Explanation

El Tor biotype produces cholera toxin (CT) but at lower quantities per bacterial unit compared to classical biotype, resulting in milder diarrhoeal illness and more asymptomatic infections (ratio of inapparent to apparent cases ~75:1 vs 4:1 for classical). El Tor has superior environmental survival and can persist in aquatic reservoirs, contributing to endemic transmission. El Tor does harbour the CTX prophage and is fully motile. The altered CT production is linked to regulatory differences, not absence of the toxin gene.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.