V. cholerae is the causative agent of potentially life threatening diarrheal disease named as cholera. Cholera is an endemic disease in Iran. Encountered increasing resistance of V. cholerae to commonly used antibiotics such as tetracycline has led to major challenges in the treatment of this disease .The present study was carried out to determine the prevalence of drug resistance as well as molecular bases of resistant V.cholerae strains which were isolated from patients in cholera outbreaks during summer of 2013 in Iran. Susceptibly testing was performed on V.cholerae strains isolated from stool of patients suffering from cholera in Iranian reference health laboratory by E -test MIC method as recommended by CLSI guideline. Antibiotic strips used included Ampicillin, Ciprofloxacin, Nalidixic acid, Cefixime , Tetracycline, Erythromycin and Trimethoprim-sulfamethoxazole .Regarding observed dominant pattern of tetracycline resistance comparing to results of previous years ,we decided to confirm the resistance by detecting the tetA , tetB and tetC by Polymerase chain reaction method. The results of antibiotic susceptibility testing revealed 100% resistance ofisolated strains to tetracycline. Data obtained from PCR reaction on resistant strains for tetA, tetB and tetC showed that 45(44.1%), 37(36.2%) and 70(68.6%) were containing tetA, tetB and tetC gene respectively. Moreover, the frequency of tetA+tetB, tetA+C, tetB+tetC , tetA+tetB+tetC also were determined as 9(44.1%), 32(36.2%), 19(%) and 8(68.6%) respectively. This study revealed the pattern of drug resistance distribution of isolates harboring tetA, tetB, tetC genes in relation to sex, age and nationality of patients
and the cities where the cases were reported. A significant correlation was obtained between reported geographical incidence and drug resistant strains.
Keywords: Tetracycline, V. cholera, Antimicrobial resistance, tet genes