Antibiotic sensitivity testing.

The Kirby-Bauer disk diffusion technique was applied to perform the antibiotic susceptibility testing according to the CLSI guidelines \citep{20172016}. The following XX commercial antimicrobial agents (Oxoid, USA) were tested against all XX 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.