Physical quality and antibiotic susceptibility profile of <i>Escherichia coli</i> isolates from roof-harvested rainwater: A microcosm study

Abstract

Owing to the inadequate supply of potable water in rural settlements in developing countries, roof-harvested rainwater (RHRW) has been favoured as an alternative source of water supply. The present study investigated the physical characteristics and microbial quality of 10 RHRW samples collected from storage tanks in Ikwo community of Ebonyi State, Nigeria. Triplicate water sampling was performed over a 3-month sampling regime. Onsite determination of odour, colour, pH and temperature, and isolation and enumeration of Escherichia coli were done using standard procedures. The identity of the isolates was confirmed using molecular techniques, and the susceptibility of the isolates to 11 antibiotics was determined following the Kirby-Bauer disc diffusion assay. Multiple antibiotic resistance phenotypes and indices (MARPs and MARI) were equally determined. Our findings revealed that the RHRWs had unobjectionable odour and were colourless. Across the 3-month o sampling, the pH ranged from 6.9 to 7.8 while the temperature was between 24 °C and 29 C. While E. coli was absent in samples E (September), H (August and October) and J (August, September, and October), the highest E. coli count in August, September, and October was 37, 32, and 38 cfu/100 mL, respectively. The antibiotic susceptibility test on 40 E. coli isolates showed high resistance to ampicillin (100%), aztreonam (98%), cefotetan (97%), nitrofurantoin (90%), imipenem (83%), streptomycin (72%), and ertapenem (69%). Interestingly, the ighest MARP, 11 (AK/S/ETP/IMI/OFX/NOR/AMP/CTT/ATM/F/TE) (sample B), and the least, 4 (IMI/AMP/CTT/ATM) were recorded in samples B and D, respectively in September. MARI was from 0.42 to 1.00. The physical parameters conform with WHO standards, on the other hand, detection of E. coli poses risks of water-borne illness(es) and transmission of antimicrobial resistance. Hence stringent measures including proper treatment, sanitation and hygiene are advocated to safeguard the health of dwellers who depend on this water source for daily life activities.