Co-occurrence of antibiotics and chlorine resistance in enterobacteriaceae isolated from groundwater sources in Ado Ekiti

Groundwater, which is heavily depended on for water needs in Sub-Saharan Africa including Nigeria, is increasingly at risk of contamination from agricultural, industrial, and sewage effluent. This poses a major threat to public health. The study investigates the co-occurrence of antibiotics and chlorine resistance in Enterobacteriaceae isolated from groundwater sources. Ten samples of groundwater were collected from each of our different locations in Ado-Ekiti (Ureje, Olokemeji, Covenant, and Dalimore). Physicochemical characterization of the water samples, isolation and molecular characterization of Enterobacteriaceae, as well as antibiotics and chlorine susceptibilities of the isolated were determined using standard methods. Results showed that electrical conductivity ranged from 152.1 µS/cm to 852.8 µS/cm, pH values varied between 5.59 and 8.7, Turbidity ranged from 2.54 to 4.66 NTU. Iron concentrations were as high as 0.63 mg/L and lead levels were up to 0.06 mg/L, surpassing WHO standards. Enterococcus faecalis, Klebsiella sp., Proteus mirabilis and Salmonella sp were the predominant isolates. Three of the isolates: Salmonella enterica (resistant to all 10 antibiotics MAR index= 1), Klebsiella sp (resistant to 9 antibiotics MAR index= 0.9), and Enterococcus faecalis (resistant to 4 antibiotics MAR index= 0.4) were multidrug resistant, while Proteus mirabilis was resistant to ciprofloxacin only. The isolates showed susceptibility to chlorine as from 0.40 mg/mL, Enterococcus faecalis was the most susceptible to chlorine, while Klebsiella pneumoniae was the most resistant (16.50 mm at 1.00 mg/mL). These findings highlight a critical public health concern, as the dual resistance of groundwater-associated Enterobacteriaceae undermines the goal of conventional water treatment protocols, therefore enhanced monitoring and improved disinfection strategies are urgently recommended to safeguard community health.