Objectives: Cholera is an endemic disease in Iran and some cases of this disease are reported throughout the world annually. The aim of this study was to determine epidemiology and antimicrobial resistance patterns of Vibrio cholerae O1 biotype ELTor serotype Inaba in 2005 summer outbreak in Iran.

 Methods: Stool samples were collected from patients suspected of having cholera who were admitted to hospitals and clinics and then were cultured in TCBS. Specimens examined by confirmed bacteriological methods and ultimately they were serotyped by special antiserums. Finally 5% of the isolates were sent to Cholera Reference Laboratory for confirmation, serotyping and susceptibility testing. Antimicrobial susceptibility testing was performed by disk diffusion methods and E-test minimal inhibitory concentration (MIC) as recommended by NCCLS.

 Results: Totally, 1118 patients were to have cholera the epidemicity. The Disease was reported from twenty six provinces. The majority of cases were reported from Tehran, Qum and Hamedan with 219, 190 and 150 cases respectively. 50% of patients were between 15-34 years old. 53% of patients were male and 47% female. 97.7% of patients had Iranian nationality, 2.3% were from Afghanistan and Pakistan. 20% of patients were hospitalized and 80% were treated as outpatients. Case mortality rate was 1%. 1104 isolates were Inaba serotype and only 14 cases were ogawa serotype. Our studies revealed that the origin of Vibrio cholerae was consumption of raw vegetables that were watered by sewage. We also isolated V. cholerae from sewages. All isolates were resistant to Co-trimoxazole, Nalidixic acid, Furazolidone, and intermediate to Chloramphenicole. All isolates were susceptible to Tetracycline, Ciprofloxacin, and Erythromycin. MIC for Co-trimoxazole and Nalidixic acid were over 256µg/ml and 1.5µg/ml for Erythromycin. The antibiogram results showed that all isolates had the same origin.

 Conclusion: Our study reveals that, unlike previous epidemics, the causative agent of cholera in summer outbreak of 2005 was V. Cholerae ELTor, serotype Inaba. Concering the similar antibiogram pattern they had the same origin.