Development of polymerase chain reaction for detection of predominant streptococcal isolates causing subclinical bovine mastitis

Bovine mastitis is the most important source of loss for the growing dairy industry. Streptococci, with special reference to Streptococcus agalactiae, S. dysgalactiae and S. uberis, are the predominant pathogens causing bovine mastitis. A rapid, sensitive and specific test for the detection of these pathogens needs to be developed. To accomplish this, initially 163 milk samples were collected from various organized and unorganized sectors in and around Bangalore, India. These milk samples were screened for subclinical mastitis by somatic cell counting (SSC) and electro conduction (EC). Of these, 131 samples selected based on SCC and EC values were subjected for isolation of the organisms. Two sets of specific primers, targeting streptococcal 16S rRNA gene were designed for detection of S. agalactiae, S. dysgalactiae and S. uberis. The results of the study showed S. agalactiae as the predominant streptococci among the generally identified streptococcal species associated with subclinical bovine mastitis in dairy cattle in and around Bangalore.