A total of 90 market milk samples collected from Tirupati and its surrounding areas were used for isolation of Staphylococcus aureus. Out of 90 milk samples, 48 isolates were found as purple coloured cocci in clusters on gram staining. All the 48 isolates were confirmed as pathogenic Staphylococcus aureus by a positive coagulase test. The biochemical tests like IMViC tests, urease test, oxidase test, nitrate reduction test and catalase tests, confirmed the presence of Staphylococcus aureus. DNase test revealed the presence of blue to purple coloured colonies with clear zones around the colonies which are the characteristic colonies on DNase agar. On blood agar plates, the positive isolates produced β haemolysis. A panel of 14 antibiotic discs were tested by using the standard disc diffusion method. Among the 48 isolates all of them were not resistant to Vancomycin (0%). Maximum resistance was observed for cefotoxim (77.50%), followed by, ampicillin (48.24%), penicillin (43.96%), gentamycin (43.00%), streptomycin (38.80%), ciprofloxacin (31.50%), tetracycline (31.20%), cefoperazone (25.60%), erythromycin (23.86%), cephoxitin (23.11%), oxacillin (17.83%) Azithromycin (15.70%) and cephalothin (14.82%).
