Prevalence and associated risk factors of High-Level Vancomycin-resistant Enterococcus faecium in well water used for domestic purposes in Ile-Ife, Southwestern Nigeria

Vancomycin-resistant Enterococcus faecium (VREfm) has emerged as a significant global public health threat. While hospital-acquired transmission is commonly implicated in outbreaks, contaminated water sources may contribute to the environmental dissemination of VREfm. This study aimed to determine the prevalence of VREfm and identify associated environmental risk factors in domestic well water in Ile-Ife, southwestern Nigeria. We assessed 350 wells for VREfm, and questionnaires were administered to obtain information about well characteristics and owner biodemographics. Isolates were identified using microbiological and molecular methods. The isolates were tested against eight antibiotics using the Kirby-Bauer disk diffusion method, and the vancomycin minimum inhibitory concentration (MIC) was determined by the agar dilution method. The resistance genes ( vanA, vanB, msrA/B, mefA, mph(ABC) ) and virulence genes ( esp, gelE ) of VREfm were detected by polymerase chain reaction. Data analysis was performed using R software. Thirty-eight (10.9 %) wells were contaminated by VREfm, with counts ranging from 1 × 10 2 to 5 × 10 3 CFU/100 mL. Wells with spilt water collection, ponding within three metres/Bad drainage channel, and sited within 15 m of latrine/septic tank significantly harboured VREfm ( p < 0.05). All isolates (100 %) exhibited resistance to tetracycline, penicillin, erythromycin, and vancomycin. The vancomycin MIC of the isolates ranged from 64 to 512 µg/mL. Twenty-seven (71.1 %) of 38 isolates harboured only the vanA gene, while one (2.6 %) harboured both the vanA and vanB genes. Five isolates (13.2 %) harboured the msrA/B gene, three isolates (7.9 %) harboured only the mph(ABC) gene, one isolate (2.6 %) harboured both mph(ABC) and mefA genes, and four isolates (10.5 %) harboured only the mefA gene. Virulence determinants, esp and gelE were detected in 2.6 % and 29 % of the isolates, respectively. The detection of VREfm in well water highlights the potential public health risks associated with the consumption of untreated water. Consequently, there is a necessity for routine sanitation practices and rigorous structural inspections of wells to mitigate ponding, spilt water accumulation, and the potential for waterborne disease outbreaks.