Abstract

The presence of multidrug-resistant enteric bacteria in domestic water sources is a growing public health concern. This study evaluated the bacteriological quality, molecular identity and antibiotic resistance profile of bacteria isolated from tap (government treated potable water), rain, upstream and downstream river water sources in Isiala-Ngwa North and South Local Government Areas, Abia State, Nigeria. Twenty-four water samples were collected monthly over three months (May–July 2025) and analyzed using standard microbiological, biochemical, molecular (16S rRNA) and antimicrobial susceptibility (disc diffusion) methods. Total heterotrophic bacterial counts ranged from 1.3×10³ to 9.2×10³ CFU/mL and total coliform counts ranged from 1.2×10¹ to 6.0×10¹ CFU/mL, exceeding recommended safe limits of the WHO guidelines across all sources. Forty bacterial isolates belonging to eleven genera were recovered and identified biochemically, with Citrobacter sp. (30.0%) the most prevalent, followed by Serratia sp. (17.5%) and Klebsiella sp. (15.0%). Molecular identification by 16S rRNA sequencing confirmed Citrobacter freundii, Proteus mirabilis, Klebsiella pneumoniae and Enterobacter cloacae among the isolates. Hemolysis assays showed 47.5% β-hemolysis, 40.0% α-hemolysis and 12.5% γ-hemolysis. Antibiotic susceptibility testing revealed high resistance, with 100% of isolates resistant to streptomycin and augmentin, and multiple antibiotic resistance (MAR) indices ranging from 0.25 to 1.0 in all isolates; ciprofloxacin retained the highest activity (97.5% susceptibility). These findings indicate that the water sources examined harbors multidrug-resistant enteric bacteria; and are therefore bacteriologically unsafe for direct consumption. Therefore, routine bacteriological surveillance and appropriate treatment of these water sources before domestic use are recommended.