Authors : Raji, I. O.; Ighodalo, Omoefe I. O.; Uchenne-Nzenwata U.; D., Sirajudeen A. O.; Ganiyu L. O.; Adeneye Q. B.; Afolayan, O. J.; Oluponmile, F. E.

Volume/Issue : Volume 11 - 2026, Issue 4 - April

Google Scholar : https://tinyurl.com/2nt59fc6

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DOI : https://doi.org/10.38124/ijisrt/26apr1312

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Abstract : Domestic refrigerators are designed to maintain temperatures around 4-5°C to preserve food and prevent microbial growth. However, biofilms forming on refrigerator surfaces pose significant risks to food safety and public health by harboring pathogenic and spoilage-causing microorganisms. This study isolated and characterized bacterial and fungal biofilms from five domestic refrigerators in Abeokuta, Nigeria. Samples were collected using sterile swab sticks and cultured on nutrient agar (for bacteria) and Potato Dextrose Agar (for fungi). Bacterial isolates were identified using Gram staining, biochemical tests, and 16S rRNA sequencing; fungal isolates were identified using microscopy and ITS region sequencing. Antibiotic susceptibility testing was performed using the Kirby-Bauer disk diffusion method. Results showed 100% contamination rate. Bacterial isolates phenotypically included Streptococcus spp. (60%), Escherichia coli (20%), and Bacillus spp. (20%). Molecular identification of the dominant bacterium revealed Bacillus velezensis strain CUABAOS02 (PP657698). Fungal isolates phenotypically included Penicillium spp. (60%), Cryptococcus spp. (20%), and Aspergillus spp. (20%). Molecular identification revealed the dominant fungus as Aspergillus niger strain CUAB-AOS05 (PP657690). Phylogenetic and plasmid analyses demonstrated genetic diversity and adaptive potential. Antimicrobial susceptibility testing revealed that all bacterial isolates were multidrug-resistant, showing resistance to gentamicin, pefloxacin, ofloxacin, chloramphenicol, streptomycin, ciprofloxacin, trimethoprim/sulfamethoxazole, and erythromycin. The presence of Bacillus velezensis CUAB-AOS02, Aspergillus niger CUAB-AOS05, and multidrug-resistant organisms in domestic refrigerators is concerning. Regular cleaning, proper food storage, and consumer education are essential to mitigate health risks.

Keywords : Biofilm; Domestic Refrigerator; Bacillus Velezensis; Aspergillus Niger; Multidrug Resistance; Food Safety.

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