Abstract

The objective of this study was to determine whether there was an association of seasonal variation and bacterial communities of municipal water. The sampling was carried out fortnightly after a flow time of 5 min to eliminate any contaminant present in the mouth of tap in sterilized screw caped 500 ml white glass flasks (Pyrex), containing 0.1 ml of a 1.8% solution of sodium thiosulphate pentahydrate (Na₂S₂O₃.5H₂O) per 100 ml of sample. Samples were placed in ice boxes and brought to laboratory within 1 h of collection. Samples were analyzed for bacterial communities using standard microbiological method (membrane filtration technique). The suspected colonies were then further purified and identified using API 20E (BioMerieux) commercial identification kit. Twelve pathogenic bacterial species were isolated and identified from municipal water on conventional and selective media.Their prevalence was higher in summer season. The average isolation rate was as follows: Escherichia coli 69.4%, Proteus mirabilis 65.2%, Providencia rettgeri 65.2%,Providencia stuarti 61%, Klebsiella oxytoca 54.1%, Citrobacter youngae 60%, Non fermenter species 57%, Chryseobacterium meningosepticum 51.3%, Vibro mimicus39%, V. cholerae 38%, Aeromons hydrphilia 65.2% and Pseudomonas aeruginosa78%. It is important to mention that water samples were positive for the above pathogens throughout the study period (2005 to 2007). The temperature of water samples was reported highest in July to September and the pH of water samples ranged 7 and 7.8. The bacteriological quality of drinking water under study was very poor. In summer, the isolation rate of bacterial communities was higher than in winter

Key words: Waterborne pathogens, drinking water, contamination.