Listeriosis

Analysis of microorganisms isolated from refrigerator surfaces and interiors is crucial for assessing the cleanliness and potential health risks associated with these appliances. Microorganisms that thrive in low temperatures (psychrophiles) can cause food spoilage and pose a health risk through foodborne diseases such as Listeriosis, Botulism, Salmonellosis, and Diarrhea. Therefore, it is essential to identify the types and concentrations of microorganisms present in different areas of refrigerators. This study aimed to evaluate the microbial quality of refrigerator exteriors and interiors in homes. Swabs and air samples were collected from 15 refrigerators in Ugbowo city and analyzed in a certified microbiology laboratory. Questionnaires were completed by refrigerator owners. Biochemical tests were used to further characterize the isolates. Antibiotic susceptibility testing was performed to determine the sensitivity or resistance of the identified isolates to various antibiotics. The results showed that the lowest microbial count was observed in refrigerators cleaned weekly (3.01 ± 0.41 CFU/ml), while the highest count was observed in refrigerators cleaned once a month (3.29 ± 0.33 CFU/ml). The lowest microbial count was observed in refrigerators with 5-9 hours of electricity supply (2.74 ± 0.20 CFU/ml), and the highest count was observed in refrigerators with 15-19 hours of electricity supply (3.56 ± 0.00 CFU/ml). The lowest microbial count was observed in refrigerators without external power supply (2.61 ± 0.79 CFU/ml), while the highest count was observed in refrigerators with external power supply (3.25± 0.31 CFU/ml). All identified isolates were 12 susceptible to gentamicin antibiotics, while they were all resistant to erythromycin, metronidazole, carbenicillin, and cefoperazole antibiotics. All identified microbial isolates except S. enterica were susceptible to iprofloxacin, and all identified microbial isolates except E. coli were resistant to tetracycline antibiotics. The Susceptibility Index suggests that E. coli is the most susceptible to the antibiotics used, with the lowest Susceptibility Index value of 0.5, while S. enterica is the most resistant and least susceptible, with the highest value of 0.75. Both are indicators of high-risk contamination sources, according to Davis and Brown (2016), with a value of ≥0.2 or higher being indicative of a "high-risk" contamination source. These results demonstrate the presence of various types of microorganisms in refrigerators. Domestic refrigerators may be considered as a significant potential source of foodborne illnesses. Therefore, it is imperative to educate households, laboratories, and the general public about proper refrigeration practices. Regular (weekly) and thorough cleaning of refrigerators is essential to reduce the presence of microorganisms/microbial load