Microbial Contamination of Dishwares and Dishwashing Water in Tertiary Institution Restaurants: Implications for Food Safety and Public Health in Offa, Nigeria

Abstract

Background: Foodborne diseases attributable to contaminated food-contact surfaces constitute a major public health burden in developing countries. Dishware and dishwashing water in institutional food-service settings represent critical but understudied transmission vectors for pathogenic microorganisms. Aim: This study sought to evaluate the microbiological safety of dishware and dishwashing water obtained from restaurants serving a tertiary institution in Offa, Kwara State, Nigeria. Methods: Samples were collected by swabbing dishware surfaces and by directly collecting dishwashing water from two tertiary institution restaurants. Standard microbiological techniques — comprising pour-plate and streak-plate methods on Nutrient Agar, MacConkey Agar, and Potato Dextrose Agar — were employed for isolation and enumeration. Bacterial isolates were characterised using Gram staining and conventional biochemical tests (catalase, coagulase, motility, and starch hydrolysis). Fungal isolates were identified through macroscopic morphology and lactophenol cotton blue microscopy. Results: All samples yielded microbial loads that were too numerous to count (TNTC) for the total aerobic plate count (TAPC), total coliform count (TCC), and total fungal count (TFC). The bacterial isolates included Staphylococcus aureus, Escherichia coli, and Bacillus sp. Fungal isolates comprised Aspergillus sp., Penicillium sp., Rhizopus sp., Cladosporium sp., and Fusarium sp. across the combined sample sets. Conclusion: The widespread microbial contamination documented in this study indicates notable lapses in hygiene and sanitation within the institutional food-service environments examined. The isolated organisms are associated with health risks, including gastroenteritis, aspergillosis, and mucormycosis. Food-handler training, routine microbiological surveillance, and infrastructure improvements are therefore recommended to reduce the risk of foodborne illness transmission in such settings.