Background: A study was carried out to screen milk borne Staphylococcus aureus for resistance against Beta lactam antibiotics. Methods: A total of 45 milk samples were collected over a period of three months from large animal outpatient unit of Madras Veterinary College Hospital, Chennai. Upon collection of samples, ABST followed by its growth in Mannitol Salt Agar was carried out as part of the phenotypic screening. Genotypic screening for Staphylococcus screening was done with the help of PCR by using nuc and mec A primers. MIC for ceftriaxone and cloxacillin was carried out with the samples that were found positive for Staphylococcus aureus. The antibiotic sensitivity pattern is presented: Fluoroquinolones (87.5% sensitive), aminoglycosides (72.5% sensitive), Amoxicillin-Clavulanic acid (Amoxyclave) (72.5% sensitive). The MSA positive samples were subjected to molecular identification with the help of PCR. Result: The results revealed 10 samples positive for Staphylococcus aureus and 5 among them positive for mecA gene. The MIC results were as follows: MIC50-10.95µg/ml and MIC90- 87.510.95µg/ml for ceftriaxone and MIC50- 43.75 µg/ml and MIC90- 87.5µg/ml for cloxacillin, indicating emergence of resistance. However, further studies are required in a larger sample size that can help us to attain more conclusive results.

Background: In the current scenario, the emergence of antimicrobial resistance has made it difficult to treat bacterial infections alone using antibacterial agents. Methods: Milk samples collected from 100 mastitis affected cows from August 2018 to June 2019 and were stored at 4°C. After species confirmation, isolates were subjected to ABST and screened for resistance genes - mecA, blaTEM using PCR. Minimum Inhibitory Concentration (MIC) of tetracycline and ampicillin were determined against both Staphylococcus spp and E. coli, alone and in combination with atorvastatin, vitamin D by using a modified microdilution method. Result: Staphylococcus and E. coli isolates showed 80.65% and 85.71%, 100% and 85.71% resistance against tetracycline and ampicillin, respectively. Atorvastatin and vitamin D did not display antibacterial effects as sole agents against both bacterial species. However, there was a significant decrease in the MIC of ampicillin against E. coli and Staphylococcus spp when combined with atorvastatin and vitamin D but not for tetracycline.