Identification and antimicrobial resistance pattern of Staphylococcus aureus isolated from bovine raw milk in Addis Ababa, Ethiopia

Abstract

Milk and its products are highly susceptible to microbial attack because of their rich composition. Therefore, the current cross-sectional study was conducted from November 2013 to April 2014 to isolate Staphylococcus aureus (S. aureus) and evaluate its in vitro antimicrobial resistance pattern from bovine raw milk of lactating dairy cows of five private dairy farms of Addis Ababa, Ethiopia. A total of 267 milk samples were randomly and aseptically collected and tested using bacteriological and antibiotic susceptibility tests. The findings were analyzed using WHONET 5.6 and SPSS Version 16 Softwares. The phenotypic results showed that out of the total 267 cultured raw milk samples 14(5.24%) were found to be coagulase positive S. aureus. All the positive isolates were subjected to antibiotic susceptibility tests against twelve antimicrobial agents of different antibiotic classes. The antibiogram profile of the tested S. aureus results revealed as large proportions of the isolates were found to be highly susceptible to Streptomycin (71.4%), Trimethoprim/Sulfamethoxazole (71.4%), Kanamycin (64.3%), Chloramphenicol (57.1%), Gentamycin (57.1%), and Methicillin (57.1%). However these isolates were highly resistant to Amoxicillin (78.6%), Tetracycline (78.6%), Ampicillin (71.4%), and Cloxacillin (57.1%). But the isolates were showed intermediate response to Neomycin (57.1%) and Polymyxin B (28.6%). Of the tested isolates 92.9% were developed a multidrug resistant. Hence, there should be a practice of proper use of antibiotics and hygienic measures in the farms, and genotypic based studies should be undertaken.