Isolation and Characterization of Escherichia Coli From Drinking Water of Kathmandu with Respect to Antibiotic Susceptibility and Heavy Metals Resistance Pattern

Abstract

Water deficit and deteriorating of water quality in Kathmandu is of great concern. The pollution of drinking water is responsible for a large number of mortalities and morbidities due to water–borne diseases. A study was carried out to evaluate the quality of drinking water of Kathmandu valley, was conducted from August 2008 to March 2009 in the laboratory of Central Department of Microbiology, Kirtipur. A total of 102 tap water samples were randomly collected from different areas of Kathmandu. These samples were analysed for physicochemical and microbiological parameters to assess the drinking water quality. E. coli isolated from these water samples were subjected to antibiotic susceptibility testing and heavy metals resistance pattern.

The seasonal variation in temperature was observed with the highest and the lowest temperature being 25.70C and 11.80C respectively. No variation was seen in the pH values of the water samples with all the values lying within the WHO recommended limit (6.5-8.5).

Out of 102 water samples 86.2% and 19.6% of the samples were found to contain total coliform and thermotolerant coliform respectively beyond the guideline value as recommended by the WHO (0 CFU/100 ml). A total of 20 E. coli isolates were obtained. Antibiotic susceptibility testing revealed resistance of E. coli isolates mainly towards Cephalexin (65%) followed by Amoxycillin (45%) and Tetracycline (15%). All the isolates were 100% sensitive to Co-trimoxazole, Amikacin, Chloramphenicol, Ceftriaxone, Ciprofloxacin, Nalidixic Acid and Gentamicin. The study of heavy metals resistance pattern revealed that 66.6% of E. coli isolates that exhibited resistance to more than one antibiotics had high MIC values for a set of heavy metals. All isolates exhibited high resistance to Zinc with average MIC 679.2 µg/ml and low resistance to Mercury with average MIC 58.3µg/ml.