Influence of Some Physicochemical Stresses on the Survival of Vibrio cholerae O1 at Non-Culturable State

Survival study of toxigenic Vibrio cholerae O1 Classical Inaba and El Tor Ogawa biotypes was carried out in artificial microcosm without any nutrients under stressed physiochemical conditions. The organisms were found to undergo viable but non-culturable (VBNC) state, which was detected by polymerase chain reaction (PCR) technique using primers that flank a specific fragment of the cholera toxin gene (ctx). The findings of the study showed that about 89% of samples gave positive result although the organisms were in nonculturable state. Depending upon the conditions the Classical biotype of vibrios had undergone non-culturable state within 2-15 days and 55-92 days were subjected to PCR assay after 45 and 120 days of incubation respectively. A similar tend was also observed in case of El Tor biotype. With non-culturable cell only 5 of 18 microcosms (of both Classical and El Tor biotypes) at pH 4.5 showed no viability. Since the PCR assay demonstrated positive results after 90 (in case of El Tor biotype) and 120 days (in case of Classical biotype), the total survival time thus ranges over 3 and 4 months. Thus PCR has an important advantage over the techniques those are used in routine laboratories for the identification of pathogenic organisms. Keywords: Physicochemical stresses, Survivality, Vibrio cholerae, Artificial microcosms, Polymerase chain reaction (PCR), Non-culturable state, Viable but non-culturable (VBNC)DOI: http://dx.doi.org/10.3329/bjm.v24i2.1258 Bangladesh J Microbiol, Volume 24, Number 2, December 2007, pp 133-136