Molecular Detection of Staphylococcus aureus by polymerase chain reaction assay in mastitic milk
Staphylococcus aureus is a leading cause of mastitis throughout the world. The aim of the present study was to detect S.aureus directly from mastitic milk using polymerase chain reaction assay (PCR) based on 16S to 23S rRNA intergenic spacer. 564 milk samples were subjected to PCR assays and bacteriological examination. Samples were processed for DNA extraction by phenol chloroform isoamyl alcohol method and then amplified using PCR assay. In case of S.aureus positive milk samples, amplified product size of 420 bp was obtained using optimum concentration of primers, 2X master mix and annealing temperature. Of 564 milk samples, 172 milk samples (30.49%)were characterized as S.aureus by bacteriological examination and other biochemical tests while PCR assay was able to detect 188 (33.33%) samples positive for S. aureus. None of the culturally positive milk sample was found negative by PCR based molecular detection of S. aureus. PCR assay was found rapid, sensitive and specific tool for screening large dairy herd for early diagnosis of mastitis.