Dissemination of Polymyxin B Sensitivity in El Tor Vibrio cholerae O1 Strains in Odisha, India.

The Vibrio species undergo cryptic changes in their genetic material for better adaptability, which accounts for antibiotic resistance. In the present study, we investigated the emergence and spread of sensitivity to polymyxin B (PB) by El Tor V. cholerae O1 strains from 1995 to 2019 in Odisha, India. The results showed that out of 1200 V. cholerae O1 strains, 89.4% were resistant and the remaining 10.6% strains were sensitive to PB. The sensitivity to PB of V. cholerae O1 strains emerged from 2005 to 2019, except in 2015, clearly signifying the presence of classical biotype characteristics in the El Tor variant of V. cholerae O1 strains. The Etest assay revealed some interesting traits of PB susceptibility in the ctxB1 and ctxB7 genotypes of V. cholerae O1 strains. The minimum inhibitory concentration (MIC) of ctxB7 genotypes showed reduced MIC values of ≤ 4 µg/mL, whereas ctxB1 genotypes exhibited higher MIC values of 24 and 32 µg/mL.