Vol. 8, Issue 9 (2019)

Author(s):
K Harish, A Jagadeesh Babu, T Madhava Rao, B Somasekhara Goud and Y Suresh

Abstract:
The present study was undertaken to isolate the Staphylococcus aureus from raw milk samples obtained from local vendors, to study their antibiotic sensitivity/resistant patterns, the molecular characterization of species specific Staphylococcus aureus and their methicillin resistance and tetracycline resistance by using the primers derived from nuc and tetK genes which gave specific amplification product of 270 bp and 360 bp for S. aureus and tetracycline resistance respectively. Out of 400 samples collected from different sources, 374 samples were positive for Staphylococcus aureus, Among the 374 isolates 191 isolates were confirmed as pathogenic S. aureus by a positive coagulase test. A pannel of 8 antibiotic discs were tested by using the standard disc diffusion method. Among the 191 isolates maximum resistance was observed for penicillin (74.9%) followed by gentamycin (27.2%), erythromycin (21%), cefoxitin (15.2%), and ciprofloxacin (11.5%), tetracycline (7.8%), cotrimoxazole (5.8%), chloramphenicol (0.5%). Out of 400 samples 374 samples were positive for S. aureus by cultural methods and 191 (51.07%, 191/374) were positive by PCR method. All the coagulase positive S. aureus isolates (191) were positive for nuc gene. In the present study for all the tetracycline resistant S. aureus isolates PCR assay was conducted by targeting tetK gene. Out of 15 tetracycline resistant S. aureus isolates 12 isolates were positive for tetK gene. This accounts for 6.3% of the total S. aureus isolates.