The Kirby-Bauer disk diffusion technique was applied to perform the antibiotic susceptibility testing according to the CLSI guidelines (36). The following 14 commercial antimicrobial agents (Oxoid, USA) were tested against all 34 V. cholerae isolates: ampicillin, cefotaxime, streptomycin, chloramphenicol, erythromycin, azithromycin, co-trimoxazole, tetracycline, nalidixic acid, norfloxacin, ciprofloxacin, nitrofurantoin, polymyxin B, and furazolidone. Escherichia coli ATCC 25922 was used for quality control for the Kirby-Bauer disk diffusion tests. Isolates which exhibited resistance to at least three or more antibiotic classes were considered multidrug-resistant (MDR) isolates. Further, isolates with an intermediate zone of inhibition were also considered resistant.