Bacteriological examination of hundred water samples twenty five each from streams, Dal lake, tube wells and community supply water (CSW) in Srinagar was conducted during year 2009. The positivity percentage of samples obtained from streams, Dal lake, tube wells and CWS for coliforms was 100, 100, 92 and 56 respectively. The 60 isolates of E. coli were serotyped at NSECRI, Kasauli, Himachal Pradesh. The results indicated that 56 (93.33%) of the isolates were grouped into 22 different (O)-groups and other four strains were rough type. The most predominant serogroups were O152, O84, O86, O2, O78, O157, O141, O59, O63, O109, O09, O13, O91, O164, O45, O120, O88, O25, O3, O24 and O56. One strain of O157 which causes hemolytic uremic syndrome was recovered from samples from stream water, while two other strains were recovered from Dal Lake. None of the samples from tube wells or/CWS showed the presence of O157. The recovery of different pathogenic strains of E. coli from different water sources poses a great threat to human health.
Many developing regions suffer from either chronic shortages of freshwater or the pollution of readily accessible water resources (Lehloesa and Muyima, 2000). According to a recent UNICEF report, about 800 million people in Asia and Africa are living without access to safe drinking water. Consequently, this has caused many people to suffer from various diseases (Tanwir et al., 2003). The quality of drinking water is of vital concern to mankind, since it is directly associated with human life. Fecal pollution of drinking water causes water-borne diseases, which wiped out entire population of cities (Farah et al., 2002). According to the special report of United Nations on developing countries, the population in these areas is exposed to higher risks of enteritis, diarrhea and contagious diseases, due to non-availability of safe and portable drinking water (OCHA, 2001). The major hazard in drinking water supplies is microbial contamination arising as a result of agricultural land wash, domestic sewerage, industrial effluents, improper storage and handling (WHO, 2006; Saha et al., 2006). More than 250 million cases of water borne diseases are reported every year resulting in more than 10 million deaths in tropical countries (Synder and Merson, 1982).
Material and Methods
The sample collection was carried out following the standard procedure as outlined by American Public Health Association, (1992). A total of 100 water samples of 250ml size were collected in sterilized neutral glass bottles provided with ground glass stoppers and the neck protected by aluminium foil. The samples of finished or table water were collected in sampling bottles added with a sufficient quantity of sodium thio-sulfate (0.1ml of 3% solution in 170ml sample) to neutralize residual chlorine or chloramines before sterilization. The samples were brought to the laboratory within 8 hours of collection and processed either immediately or stored at refrigeration temperature for processing in any case within 18 h of collection.
Processing of Samples
The samples were processed for isolation and identification of E. coli using a standard protocol given by Cowan and Steel (1993). All the isolates were confirmed by various standard cultural, morphological and biochemical tests.
The isolates after confirmation by various cultural, morphological and biochemical tests were sent to National Salmonella and E. coli Central Research Institute, Kasauli, Himachal Pradesh for serotyping.
Results and Discussion
All the 60 isolates of E. coli were serotyped at NSECRI, Kasauli, Himachal Pradesh. The serotyping was based on O-antigenic character. The results indicated that 56 (93.33%) of the isolates were grouped into 22 different (O)-groups. The other four strains were rough type. The serotypes recovered in the present investigation were O78, O63, O09 and O25 (Enterotoxigenic E. coli, ETEC); O86, O109 and O13 (Enteropathogenic E. coli, EPEC); O141, 059, 0 rough, O2, O88, O120, O45, O91, O84 and O157 (Shiga-toxin producing E. coli); O164 and O152 (Entero-invasive E. coli, EIEC); and O3, O24, O56 (Entero-aggregative E. coli, EAEC). Among these O152, O84, O86, O88, O78, O157, O141 and O24 were the most commonly recorded serotypes (table 1). A considerable variation in the occurrence of different serogroups in different sources was observed. Serogroups O152, O84 and O86 were recovered from all the sources under study. One strain of O157:H7 which causes hemolytic uremic syndrome was recovered from samples from stream water while two other strains were recovered from Dal Lake. The recovery of strains O157 recovered
Table-1. Serogroups of E. coli isolated from different sources of water
|Source||No. of Isolates||Most Common Serotypes|
|Streams||16||O152 (3), O84 (3), O86 (2), O78 (2), Rough (2), O3 (1), O 91(1), O164 (1) and O45 (1).|
|11||O152 (3), O84 (2), O56 (2), O157 (1), O141 (1), O59 (1) and O86 (1)|
|Dal Lake||25||O152 (3), O84 (3), O78 (2), O157 (2), O141 (2) Rough (2), O88 (1), O25 (1), O24 (2), O63 (1), O109 (1), O09 (2), O2 (1), O13 (1), O120 (1),|
|08||O86 (2), O152 (1), O84 (1), O59 (1), O24 (1), O63 (1) and O109 (1)|
Figures in the paranthesis represent the number of different serotypes
from Dal Lake and streams can be traced to the direct contamination of Lake/stream by waste water disposal, use of animal and human excreta for vegetable cultivation in floating gardens and cattle and sheep grazing on its embankment. None of the samples from tube wells or/and CWS showed the presence of O157. Laura (2009) recovered E. coli O157:H7 from eastern part of the Wildcat Creek watershed, Kokomo. Ramteke et al., 2007, recovered O4 (Uropathogenic E. coli, UPEC), O25 (Enterotoxigenic E. coli, ETEC), O86 (Enteropathogenic E. coli, EPEC), O103 (Shiga-toxin producing E. coli, STEC), O157 (Shiga-toxin producing E. coli, STEC), O8 (Enterotoxigenic E. coli, ETEC) and O113 (Shiga-toxin producing E. coli, STEC) serotypes of E. coli from different drinking water sources. Willayat et al, 2003, isolated O157, O141, O09 and O19 serotypes of E. coli from various drinking water sources of Srinagar city. McCarthy and Barrett (1995) recovered a O157:H7 strain of E. coli from a contaminated lake in Connecticut and found that the isolated stain was the causative agent of hemolytic uremic syndrome in the region. The recovery of different pathogenic strains of E. coli especially O157:H7 poses a serious threat to human health as these serotypes can cause a number of health hazards ranging from diarrhoea to extra-intestinal infection such as septicemia and urinary tract infection.
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