Bacteriological quality, antibiotic susceptibility pattern of isolates and associated factors among raw cow’s milk collected from cafeterias in Adama Town, Oromia Region, Ethiopia

Abstract

Background: Milk is an excellent medium for the growth of microorganisms because it is composed of water, nutrients, and an almost neutral pH, and consuming such pathogens is hazardous to human health. Based on our knowledge,
there is currently no published research available regarding the bacteriological quality of raw cow's milk sourced from
cafeterias in Adama Town.
Methods: A cross-sectional study was conducted in Adama Town, Oromia Region, Ethiopia, from March 23 to June
6, 2019. The study included 115 randomly selected samples of raw cow's milk obtained from cafeterias. Questionnaire
was used to collect data on handling practices. The milk samples were cultured on Eosin methylene blue agar, mannitol
salt agar, and Salmonella-Shigella agar to determine the total and coliform count using serial dilutions. The antibiotic
susceptibility testing of the bacterial isolates was assessed using the Kirby-Bauer disk diffusion method on MullerHinton agar. The data were analyzed using Statistical Package for the Social Sciences (SPSS) version 22. A logistic
regression model was used to assess the association between predictors and milk quality and a p-value of less than
0.05 was considered statistically significant.
Results: The overall mean ± standard error of total bacterial and coliform counts of sampled milk were 6.600 ± 0.144
and 4.96 ± 0.10 log10 CFU/mL, respectively. Based on 2009 Ethiopian standards for the bacteriological quality of
raw milk, 71.3% of the samples were of poor quality, and 67% of them also tested positive for total coliforms. Staphylococcus aureus (23.5%) and Escherichia coli (7.8%) strains were identified in the milk samples. All E coli isolates
were found to be resistant to ampicillin, but susceptible to amoxicillin-clavulanic acid, ceftriaxone, gentamicin, cotrimoxazole, ciprofloxacin, tetracycline, chloramphenicol, cefoxitin . The majority of Staphylococcus aureus isolates
showed resistance to one or more of the tested antibiotics.
Conclusions: In this study, more than seven out of ten milk samples had significant levels of bacterial contamination. Multidrug resistance was observed in nearly half of the total tested isolates. Adequate sanitary measures,
hygienic practices, strict monitoring, and quality control measures should be in place to ensure the delivery of safe
and quality milk to consumers.