Pathogenicity and Antibiotic Resistance of Bacteria Isolated from Reused Dish-rinsing Water in Informal Restaurants in Daloa (Côte d’Ivoire)

Abstract

Background: In Daloa (Côte d’Ivoire), the reuse of dish-rinsing water in informal (street food) restaurants is a common practice that may constitute a major source of microbial contamination and the dissemination of antibiotic-resistant bacteria. Aims: This study assessed the physicochemical and microbiological quality of such water, identified the bacterial species present, and analysed their resistance profiles. Place and Duration of Study: The research was conducted at the Laboratory of Agrovalorisation, Department of Biochemistry-Microbiology, Jean LOROUGNON GUEDE University of Daloa, from February 2025 to March 2025. Methodology: Thirty samples collected from ten restaurants in the Tazibouo district were analysed for pH, mesophilic aerobic germs (MAG), total coliforms, Escherichia coli, Salmonella spp., and Staphylococcus aureus. Isolates were identified using biochemical methods and tested for antibiotic susceptibility according to EUCAST (2025) guidelines. Resistance genes for β-lactams (bla_TEM, bla_SHV, bla_CTX-M), quinolones (qnrA, qnrB, qnrS), colistin (mcr-1) were detected by PCR. Results: The results showed that 40% of the samples had a pH outside the recommended range and that most exceeded microbiological standards; Salmonella spp. was present in 10%, E. coli in 70%, and S. aureus in 80% of the samples. Klebsiella oxytoca was the predominant species (66.66%) and displayed complete resistance to amoxicillin-clavulanic acid and, in 29% of cases, resistance to fluoroquinolones and chloramphenicol. The most frequently detected resistance genes were bla_TEM and qnrA, whereas mcr-1 was not found. Conclusion: These findings indicate that reused dish-rinsing water in these establishments is a potential reservoir of multidrug-resistant bacteria and poses a significant public health risk, underscoring the urgent need to improve hygiene practices, increase the frequency of water replacement, and implement regular monitoring.