Occurrence and antimicrobial susceptibility profiles of Escherichia coli and Salmonella spp. from unbranded and branded yogurt in Addis Ababa, Ethiopia

The rapid growth of the Ethiopian dairy supply chain has raised concerns regarding food-borne pathogens and antibiotic-resistant bacteria. Therefore, it is crucial to have reliable methods for identifying bacteria and testing their susceptibility to antimicrobials in order to address public health concerns. The Vitek 2XL compact system is emerging as a promising tool due to its user-friendly nature and faster reporting times for microbial identification and antimicrobial susceptibility testing (AST). However, its application in yogurt analysis has been limited so far. To the best of our knowledge, this study is the first to use the Vitek 2XL system to assess the occurrence and antimicrobial susceptibility profiles of Escherichia coli, Salmonella spp., and Staphylococcus aureus isolates from unbranded and branded yogurt sold in Addis Ababa, Ethiopia. The findings from this research provide valuable insights into yogurt safety and aim to improve food safety practices in the region. A total of 40 yogurt samples, consisting of 20 branded and 20 unbranded were collected from retail markets. The samples were cultured using International Organization for Standardization reference analytical methods. The VITEK 2 XL Compact system (bioMérieux) was employed to confirm the presumptive colonies and perform antimicrobial sensitivity testing, following the manufacturer’s instructions. The overall prevalence of E. coli and Salmonella spp. was 14/40 (35%) and 3/40 (7.5%), respectively. However, S. aureus was not detected in the examined yogurt samples 0/40 (0%). The antimicrobial susceptibility testing revealed that 7% to 28% of E. coli isolates were resistant to 13 different antibiotics. However, high susceptibility was observed to Gentamicin (100%), Amikacin (93%), Marbofloxacin (93%), and Pardofloxacin (93%). For Salmonella spp., all isolates were resistant to Ampicillin (100%), Pardofloxacin (100%), Doxycycline (100%), and Tetracycline (100%). In contrast, 67% of Salmonella spp. isolates were susceptible to Amoxicillin/Clavulanic acid (67%), Cefpodoxime (67%), Cefovecin (67%), Ceftiofur (67%), and Neomycin (67%). The results indicate that the tested yogurt samples may pose a risk of foodborne illnesses due to the presence of pathogenic bacteria. Additionally, the findings highlight a public health concern related to potential antibiotic resistance.