Demonstration of viable but nonculturable Vibrio cholerae O1 in fresh water environment of India using ciprofloxacin DFA-DVC method

AIM: To demonstrate the presence of culturable and nonculturable viable pathogenic Vibrio cholerae O1 in fresh water environments of a cholera-endemic region in India. METHODS AND RESULTS: Conventional culture and ciprofloxacin DFA-DVC were utilized to investigate the existence of V. cholerae O1. We isolated pathogenic culturable V. cholerae O1 from water samples collected from cholera-affected areas. No culturable V. cholerae O1 was isolated from water and plankton samples from natural fresh water bodies. Ciprofloxacin was used for DFA-DVC as V. cholerae O1 are 100% resistant to nalidixic acid in our region. The viable but nonculturable O1 cells were demonstrated in 2.21 and 40.69% samples from natural water bodies and cholera-affected areas, respectively. CONCLUSION: Vibrio cholerae O1 VBNC could be demonstrated using modified DFA-DVC technique. Ciprofloxacin is preferable to nalidixic acid for DVC in view of existing high-level resistance to nalidixic acid in cholera-endemic areas. SIGNIFICANCE AND IMPACT OF THE STUDY: We endorse that for public health surveillance, cholera outbreak investigation and disease control water samples in addition to culture should be tested for V. cholerae using DFA-DVC.