Surveillance of vibriophages reveals their role as biomonitoring agents in Kolkata

Abstract

Cholera is a public health threat in all developing countries. Kolkata, a city in eastern India, is an endemic zone for cholera. During the course of a comprehensive investigation on the distribution of phages of Vibrio cholerae O1 and O139 in freshwater bodies in Kolkata, we were able to isolate the phages of V. cholerae O1 and O139. Vibrio cholerae O1 phages were found at all the sites and exhibited a distinct seasonal cycle, with a primary peak (13.6-17.2 PFU mL(-1)) during monsoon (June to August) in both 2006 and 2007. Vibrio cholerae O139 phages were present in the environment and were predominant during monsoon in the year 2006, except for late winter and early summer from February to April. In contrast, in the year 2007, the O139 phages could be isolated only during July to December, with the highest counts of 12.0 PFU mL(-1) determined in August. The multiplex PCR results showed that 90 samples were positive for wbe of V. cholerae O1, 32 samples for O139 (wbf) and 18 samples for both. This study shows that surveillance of vibriophages indicates the presence of V. cholerae O1 and O139 in water bodies in and around Kolkata and could therefore serve as a powerful biomonitoring agent.

Influence of hydrologic and anthropogenic factors on the abundance variability of enteropathogens in the Ganges estuary, a cholera endemic region

“…However, there was only a weak correlation between temperature and TBC (R = 0.43, P = 0.019, N = 29 for DH and R = 0.48, P = 0.002, N = 32 for HB). Contrasting with this, CVC and temperature correlated highly significant at HB (R = 0.733, P = b0.001, N = 32) which is supported by earlier findings reporting an increase of CVC with temperature in natural waters (e.g., Nair et al, 1988; Das et al, 2009;Neogi et al, 2011). However, in our case within the same estuary, but at higher salinities, CVC and temperature show a much lower correlation (R = 0.332, P = 0.078, N = 29) at DH, which stresses the importance of further environmental parameters.…”

A Novel Triplex Quantitative PCR Strategy for Quantification of Toxigenic and Nontoxigenic Vibrio cholerae in Aquatic Environments

“…Detection and quantification of V. cholerae, especially of serogroup O1/O139 strains in environmental samples, are still difficult tasks, and no international standard is available. Currently accepted cultivation-based methods take at least 48 h to obtain a final result (5) and severely underestimate the presence of O1/O139 serogroups, due to the fact that these strains predominantly enter a viable but nonculturable (VBNC) state once released from the human intestine into the environment (6,7). Alternatively, fluorescence in situ hybridization (FISH) and the direct fluorescent-antibody assay (DFA) are direct cell-based detection methods that include VBNC bacteria.…”

Isolation and characterization of novel broad host range bacteriophages of Vibrio cholerae O1 from Bengal

“…[ 15 ] We have previously reported that phages act as a biomonitoring agent in the environment, provides important insights in V. cholerae surveillance. [ 4 ] Predation on pathogenic V. cholerae may be an important factor influencing the epidemic cycle on short-time scales and may act to modify the duration and severity of cholera outbreaks. [ 16 ]…”

“…[ 3 ] Earlier studies showed a correlation between V. cholerae O1 and its phages (vibriophages) in different environmental water samples of natural water bodies. [ 4 5 ] Because of its stability and less sensitivity vibriophages appear to be better indicators and suggested to be used as a biomonitoring agent in different aquatic ecosystems. Although V. cholerae is a human pathogen, they constitute part of the normal aquatic flora also in water environments,[ 6 ] and water is established a transmission vehicle.…”

“…[ 7 ] Earlier, we reported that vibriophages exist in the natural aquatic environment between epidemic periods as a surrogate marker, leading to the conclusion that vibriophages may play a significant role in the annual cycle of V. cholerae O1 and O139 in the environment and notably in annual epidemics of cholera in Kolkata. [ 4 ]…”