Bacteriological quality and antimicrobial resistance patterns of isolates from raw milk in dairy farms in Ethiopia

Abstract

Background Food-borne illness has a significant impact on public health and the economy, affecting nearly 30% of the population in developing countries annually. Infections transmitted through milk can lead to acute and severe diseases. However, there is inadequate information available regarding the bacteriological profile and antimicrobial resistance of organisms present in raw milk. This study aimed to assess the bacteriological quality and antimicrobial resistance patterns of isolates from raw milk at different dairy farms found in Ethiopia. Methods A cross-sectional study was conducted, selecting 176 raw milk samples through a multi-stage sampling technique from August 2022- April 2023. Bacteriological tests, including Aerobic colony count, total coliform count, thermotolerant coliform count, Salmonella and Shigella detection, as well as Staphylococcus enumerations, were performed. Further bacterial identification was carried out using VITEK-2 compact, while the antimicrobial susceptibility test was determined by the Kirby-Bauer disc-diffusion technique. Data analysis was conducted using SPSS V.27, employing descriptive statistics and appropriate statistical tests. Resut The mean aerobic colony count, total coliform, thermo-tolerant coliform, E. coli, and Staphylococcus count was,3.2, 2.70, 2.69, 2.9, and 3.1 log10 cfu/ml respectively. E. coli (77%), Klebsiella spp. (5%), Salmonella spp. (1.4%), S. aureus (13.6%), S. saprophyticus (9.8%) were also isolated. Gram-negative isolates showed sensitivity for Meropenem (96.8%) and Ciprofloxacin (89.9%) but resistant against Tetracycline (62.2%) and Streptomycin (62.2%). Staphylococcus isolates showed 95.1% Sensitivity for Levofloxacin and Gentamycin but 92.6% of isolates were resistant against Oxacillin. Extended-spectrum beta-lactamase production was detected in 16.6% of gram-negative isolates, and Methicillin resistance were observed in 30% of S. aureus isolates. Conclusion The results indicate that the overall quality of raw milk is poor, containing pathogenic and antibiotic-resistant organisms. This highlights the necessity for effective control measures to enhance production, storage, and processing practices.