Slime production, DNase activity and antibiotic resistance of Staphylococcus aureus isolated from raw milk, pasteurised milk and ice cream samples

In this study, a total of 180 samples of raw milk, pasteurised milk and ice cream were analysed for the presence of Staphylococcus aureus. There were 110 S. aureus isolated from these samples, which were investigated for DNase activity, slime production and antibiotic resistance. DNase agar that was used to investigate for DNase activity revealed DNase activity in 94.5% of 110 S. aureus. Slime production of S. aureus that was investigated by using Congo Red Agar method revealed slime production in 52.7% of S. aureus. Resistance of S. aureus to different antibiotics was determined by the Kirby–Bauer disc diffusion test. Resistance to penicillin G, methicillin and bacitracin was frequent for S. aureus strains. Few numbers of the strains were resistant to erythromycin. All strains were susceptible to vancomycin, sulbactam–ampicillin, ciprofloxacin and cefaperazone–sulbactam. Slime production positive strains were tested against penicillin G, methicillin and bacitracin. No difference was found between the antibiotic resistance of slime positive and slime negative S. aureus. There was a high rate of resistance for all S. aureus isolates against penicillin G, methicillin and bacitracin.