Assessment of virulence and antimicrobial susceptibility of staphylococcus aureus from different milk samples

The study was carryout to evaluate the incidence and multidrug resistant of Staphylococcus aureus in different milk samples. Staphylococcus aureus is a major problem of public health which causes a number of human and animal diseases. The main source of infection is contaminated milk. Totally 50 raw and pasteurized milk samples were collected from three different sources such as Goat milk (15), Buffollow milk (25), and pasteurized milk (10). In order to isolate and identify the Staphylococcus aureus from these samples. The collected milk samples were cultured on nutrient agar; the presumptive Staphylococcus colonies were sub-cultured on Mannitol Salt Agar (MSA) and confirmed by using standard Bacteriological methods. Antimicrobial susceptibility pattern of Staphylococcus aureus was done by Kirby-Bauer disk diffusion method using eight antimicrobials. The prevalence of S.aureus was found to be 25 (50%) out of the total samples examined. In addition, the prevalence of S.aureus was 5 (33.3%) from Goat milk, 16 (64%) from Buffalo milk and 4 (40%) from pasteurized milk. S.aureus was more likely to occur in buffalo milk that were poorly managed and treated frequently with antimicrobials. Thus, out of a total of 25 isolates, high resistance rate was observed primarily to Methicillin 25 (100%) followed by Erythromycin15 (60%), Amoxycillin12 (48%), Vancomycin12 (48%), Gentamycin 12 (48%), Tetracycline 11 (44%), Ciprofloxacin 11 (44%), and low level of resistance to Kanamycin 8 (32%). S.aureus became almost resistant to β-lactams and Erythromycin. The virulence characters of Staphylococcus aureus were characterized phenotypically. The rate of positiveness for Protease, Lipase, β-hemolysis, β-lactamase and Slime formation were 48%, 60%, 60%, 44%, 48%.In this study we concluded that the hygiene of milk is poor and resistant strains have contaminated the milk probably during the process of milking and transportation.