The survival of Escherichia coli in tropical estuarine water has been studied under controlled laboratory conditions using
microcosms. The survival has been assessed in terms of various self purifying factors of the natural waters such as biological,
chemical and physical factors. The biological factors considered included competition from other microorganisms, predation
by protozoa and coliphages. The suitability of the chemical composition of estuarine water has been studied under chemical
factors and negative impact of sunlight has been studied under physical factors. The results revealed that sunlight exerted
maximum negative impact, followed by biotic factors contained in the estuarine water. However, the chemical composition of
the estuarine water is found to be suitable for the growth and survival of E. coli. The injury exerted by each of the above
factors was also evaluated by using a selective and non-selective medium in conjunction. It was found that sunlight resulted in
100% injury of the cells as the cells failed to develop in a selective medium. While, sunlight resulted in the extinction of 90% of
the E. coli cells within the first two hours of exposure, biotic factors took nearly 24 hours to remove the same amount of
population.
Hatha, A A M; Abhirosh, Chandran; Suson, P S; Thomas, A P; Asit, Mazumder(I W A Publishing, February 11, 2013)
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Abstract:
The objective of the study was to evaluate the survival response of multi-drug resistant
enteropathogenic Escherichia coli and Salmonella paratyphi to the salinity fluctuations induced by a
saltwater barrier constructed in Vembanadu lake, which separates the lake into a freshwater
dominated southern and brackish water dominated northern part. Therefore, microcosms containing
freshwater, brackish water and microcosms with different saline concentrations (5, 10, 15, 20, 25
ppt) inoculated with E. coli/S. paratyphi were monitored up to 34 days at 20 and 30 WC. E. coli and
S. paratyphi exhibited significantly higher (p <0.05) survival at 20 WC compared to 30 WC in all
microcosms. Despite fresh/brackish water, E. coli and S. paratyphi showed prolonged survival up to
34 days at both temperatures. They also demonstrated better survival potential at all tested saline
concentrations except 25 ppt where a significantly higher (p<0.0001) decay was observed.
Therefore, enhanced survival exhibited by the multi-drug resistant enteropathogenic E. coli and S.
paratyphi over a wide range of salinity levels suggest that they are able to remain viable for a very
long time at higher densities in all seasons of the year in Vembanadu lake irrespective of saline
concentrations, and may pose potential public health risks during recreational activities