Multidrug-resistant Escherichia coli in selected sachet water and associated public health risk assessment in Ago-Iwoye and Oru, Ogun State, Nigeria

Abstract

Safe drinking water remains essential for public health, particularly in developing regions where sachet water is widely consumed. This study assessed the physicochemical properties, bacteriological quality, antibiotic resistance, heavy metal contamination, and potential health risks of 8) selected sachet water samples. Physicochemical parameters were measured using APHA standard methods. Bacterial counts were determined by serial dilution and plate count techniques. Escherichia coli isolates were identified through colonial morphology, Gram staining, and biochemical tests. Antibiotic susceptibility was assessed by Kirby–Bauer disc diffusion, while MAR index, heavy metals, correlations, CF, HPI, and HRI were calculated. Physicochemical parameters showed moderate variation, with pH ranging from 5.80 to 7.37, EC (0.20–1.20 mS/cm), TDS (100.00–600.00 ppm), turbidity (0.90–1.90 NTU), and DO (6.10–7.20 mg/L). Organic pollution indicators were highest in W3 (BOD: 1.80 mg/L, COD: 8.50 mg/L, TOD: 11.50 mg/L). Total heterotrophic counts ranged from 0.00 to 110.00 CFU/ml, exceeding permissible limits, while coliform counts peaked at 6.00 CFU/ml. Isolates identified as Escherichia coli exhibited high susceptibility to ofloxacin (26.00–34.00 mm) but complete resistance (0.00 mm) to several antibiotics. MAR indices ranged from 0.63 to 0.75, indicating high resistance. Heavy metals were within permissible limits, with Pb up to 0.006 ppm and Fe up to 0.160 ppm. Risk indices confirmed low contamination (CF < 1; HPI: 34.65–52.15; HRI: 0.159–0.220). Despite acceptable chemical quality, bacteria contamination and multi-drug resistance pose significant public health concerns.