PCR Assays for Detecting Major Pathogens of Mastitis in Milk Samples

Bovine milk samples were collected from cases of clinical and sub-clinical mastitis, respectively and examined bacteriologically and by simplex and multiplex PCR assays for detection of Staphylococcus aureus, Escherichia coli and Streptococcus agalactiae. Escherichia coli was the most common bacteria detected in the collected samples from clinical mastitis cases followed by Staphylococcus aureus and Streptococcus agalactiae; while Staphylococcus aureus was the most common bacteria followed by Escherichia coli and Streptococcus agalactiae in samples collected from sub-clinical mastitis cases. Compared with the cultural method, the simplex and multiplex PCR assays are less time consuming. It took less than 24 hours to be completed, while identification of bacteria to the species levels by conventional microbiological and biochemical methods required more than 72 hours. In conclusion, simplex and multiplex PCR assays can be used as a rapid, sensitive and specific routinely diagnostic tool to detect the presence of Staphylococcus aureus, Escherichia coli and Streptococcus agalactiae in milk samples.