ASSESSMENT OF ANTIMICROBIAL SUSCEPTIBILITY PATTERN OF PATHOGENIC BACTERIAL PRESENT IN SELECTED YOGHURT AND MILK PRODUCTS

ABSTRACT Milk-based beverages such as yoghurt and other fermented dairy products are widely consumed across Nigeria due to their nutritional value and affordability. However, contamination arising from poor hygiene, inadequate storage, and improper handling during distribution and retailing has raised serious public health concerns. This study assessed the antimicrobial susceptibility pattern of pathogenic bacteria isolated from selected fermented milk and yoghurt products obtained from both vendors and depots within Ibadan, Nigeria. A total of fifteen (15) samples were randomly collected from different sources under aseptic conditions and subjected to microbiological and molecular analyses. Bacterial isolates were identified based on cultural, morphological, and biochemical characteristics, while antimicrobial susceptibility testing was performed using the Kirby–Bauer disk diffusion method according to the Clinical and Laboratory Standards Institute (CLSI, 2024) guidelines. Molecular analysis was conducted to detect the presence of antibiotic resistance genes, specifically blaTEM and KPC, using polymerase chain reaction (PCR) techniques. The findings revealed that samples obtained directly from depot sources were free from microbial contamination, whereas those collected from street vendors showed the presence of pathogenic bacteria such as Escherichia coli and Klebsiella pneumoniae. The occurrence rate of E. coli was 25%, while Klebsiella pneumoniae accounted for 37.5% of the total isolates. Antibiotic susceptibility results showed that both isolates were resistant to Ampicillin and Azithromycin but remained susceptible to Ciprofloxacin, Ceftriaxone, Cefoxitin, and Septrin. Molecular characterization confirmed the presence of the blaTEM gene in E. coli and the KPC gene in Klebsiella pneumoniae, indicating β-lactamase and carbapenemase-mediated resistance mechanisms, respectively. The detection of these resistance genes in foodborne pathogens underscores the growing threat of antimicrobial resistance (AMR) transmission through contaminated dairy products. This study concludes that poor handling and lack of cold-chain maintenance at the retail level are major contributors to microbial contamination and antibiotic resistance in fermented milk and yoghurt products. Strengthening hygiene practices, enforcing proper storage standards, and implementing regular antimicrobial surveillance programs are crucial steps to reduce the spread of multidrug-resistant bacteria through commonly consumed dairy foods. These findings emphasize the need for effective food safety policies, public health education, and stricter monitoring of dairy value chains to protect consumers and minimize the risk of AMR dissemination.