Isolation and Identification of Escherichia coli from Drinking Water Sources: Microbiological Quality, Antimicrobial Resistance, and Comparative Risk Assessment

Abstract

Escherichia coli (E. coli) remains the most widely accepted microbiological indicator for assessing fecal contamination in drinking water. Contaminated water continues to pose major public-health risks, particularly in low- and middle-income countries (LMICs), where inadequate sanitation, limited water-treatment infrastructure, and growing antimicrobial resistance (AMR) amplify the burden of waterborne diseases. This study conducted a comprehensive, cross-sectional microbiological assessment of tap, well, and bottled drinking-water sources. A total of 1,000 samples (400 tap, 300 well, 300 bottled) were collected and evaluated for the presence of E. coli, associated coliforms, and phenotypic antimicrobial resistance. Standard microbiological identification, biochemical confirmation, selective culturing, and antibiotic susceptibility testing (AST) were performed following international guidelines. The findings reveal significant disparities in contamination patterns: 42.5% of well-water samples, 28.7% of tap-water samples, and 4.3% of bottled-water samples tested positive for E. coli. MDR strains were detected in 31% of positive isolates, with the highest prevalence in tap water (34%) and well water (29%), and lowest in bottled water (6%). Resistance was most common against ampicillin, tetracycline, and trimethoprim–sulfamethoxazole. These results highlight urgent risks posed by untreated and intermittently treated water systems and the growing role of environmental reservoirs in the AMR crisis. Strengthening water treatment, surveillance systems, and community-level hygiene practices is essential to mitigate risks. This study contributes vital evidence to global discussions on water safety, AMR, and Sustainable Development Goal (SDG) 6.