Potential Exposure Risk Associated with the High Prevalence and Survival of Indicator and Pathogenic Bacteria in the Sediment of Vembanadu Lake, India

Prevalence of faecal coliform bacteria and the survival of Escherichia coli, Vibrio parahaemolyticus and Salmonella paratyphi were studied in the water and sediment from Vembanadu Lake in the presence and absence of protozoan predators. The density of faecal coliform bacteria ranged between mean MPN value 5080–9000/100 ml in water and 110,000–988,000/1 g in sediment (p <0.01), which was 110 times greater than in overlying water. The laboratory microcosm studies revealed that E. coli, V. parahaemolyticus and S. paratyphi showed significantly higher survival (p <0.05) potential in sediment than in overlying water both in the presence and absence of protozoan predators. The results indicate that Vembanadu Lake sediment constitutes a reservoir of pathogenic bacteria and exhibits potential health hazard from possible resuspension and subsequent ingestion during recreational activities. Therefore, assessment of bacterial concentration in freshwater lake sediments used for contact and non-contact recreation is of considerable significance for the proper assessment of microbial pollution of the overlying water and the management and protection of related health risk at specific recreational sites. In addition, assessment of the bacterial concentration in sediments can be used as a relatively stable indicator of long-term mean bacterial concentration in the water column above.

Studies on the Hydrobiology and pollution of the Vembanad Lake and adjacent waters

The Thesis deals with the entire estuarine system in totality on several parameters related to hydrography, ecology of biota, productivity and also the effects of pollution. The objective of this study has been to review the systems physical, chemical and biological features through varying periods of time at locations where human interference is high so that an overall assessment of the changing ecology could be made so as to impress on the scientific community whether remedial measures could be undertaken in sensitive areas. It is also the objective of this study to point out thrust areas where concerted efforts from a larger body of scientists and administrators who can sit together and chalk out programmes for a co-operative endeavor in monitoring the most sensitive areas and also suggest ways and means to exploit the rich and diverse resources at optimum levels with emphasis on conservation and protection from environmental degradation resulting in depletion of resources. Areas also have been identified which are potentially more productive where aquaculture could be intensified

Potential public health significance of faecal contamination and multidrug-resistant Escherichia coli and Salmonella serotypes in a lake in India

To assess the prevalence of faecal coliform bacteria and multiple drug resistance among Escherichia coli and Salmonella serotypes from Vembanadu Lake. Study design: Systematic microbiological testing. Methods: Monthly collection of water samples were made from ten stations on the southern and northern parts of a salt water regulator constructed in Vembanadu Lake in order to prevent incursion of seawater during certain periods of the year. Density of faecal colifrom bacteria was estimated. E. coli and Salmonella were isolated and their different serotypes were identified. Antibiotic resistance analysis of E. coli and Salmonella serotypes was done and the MAR index of individual isolates was calculated. Results: Density of faecal coliform bacteria ranged from mean MPN value 2900 -7100/100ml. Results showed multiple drug resistance pattern among the bacterial isolates. E. coli showed more than 50% resistance to amickacin, oxytetracycline, streptomycin, tetracycline and kanamycin while Salmonella showed high resistance to oxytetracycline, streptomycin, tetracycline and ampicillin. The MAR indexing of the isolates showed that they have originated from high risk source such as humans, poultry and dairy cows. Conclusions: The high density of faecal coliform bacteria and prevalence of multi drug resistant E. coli and Salmonella serotypes in the lake may pose severe public health risk through related water borne and food borne outbreaks

An assessment of potential public health risk associated with the extended survival of indicator and pathogenic bacteria in freshwater lake sediments

Microcosm studies were performed to evaluate the survival of Escherichia coli, Salmonella paratyphi and Vibrio parahaemolyticus in water and sediment collected from the freshwater region of Vembanad Lake (9 35◦N 76 25◦E) along the south west coast of India. All three test microorganisms showed significantly (p < 0.01) higher survival in sediment compared to overlying water. The survival in different sediment types with different particle size and organic carbon content revealed that sediment with small particle size and high organic carbon content could enhance their extended survival (p < 0.05). The results indicate that sediments of the Lake could act as a reservoir of pathogenic bacteria and exhibit a potential health hazard from possible resuspension and subsequent ingestion during recreational activities. Therefore, the assessment of bacterial concentration in freshwater Lake sediments used for contact and non contact recreation has of considerable significance for the proper assessment of microbial pollution of the overlying water, and for the management and protection of related health risk at specific recreational sites. Besides, assessment of the bacterial concentration in sediments can be used as a relatively stable indicator of long term mean bacterial concentration in the water column above

Increased prevalence of indicator and pathogenic bacteria in Vembanadu Lake: a function of salt water regulator, along south west coast of India

Prevalence of faecal indicator bacteria, Escherichia coli and pathogenic bacteria, Vibrio cholerae, Vibrio parahaemolyticus and Salmonella were analysed in Vembanadu lake (98350N 768250E), along south west coast of India for a period of one year from ten stations on the southern and northern sides of a salt water regulator constructed in Vembanadu Lake in order to prevent incursion of seawater during certain periods of the year. While the northern side of the lake has a connection to the sea, the southern side is enclosed when the salt water regulator is closed. The results revealed the water body is polluted with high faecal coliform bacteria with mean MPN value ranging from 1718-7706/100 ml. E. coli, V. cholerae, V. parahaemolyticus and Salmonella serotypes such as S. paratyphi A, B, C and S. newport were isolated and this is the first report on the isolation of these Salmonella serovars from this lake. E. coli showed highest percentage of incidence (85.6–86.7%) followed by Salmonella (42–57%), V. choleare (40–45%) and V. parahaemolyticus (31.5–32%). The increased prevalence of indicator and pathogenic bacteria in the enclosed southern part of Vembanadu Lake may be resulting from the altered flow patterns due to the salt water regulator.