Multiplex PCR for rapid detection of Streptococcus agalactiae, Streptococcus uberis and Streptococcus dysgalactiae in subclinical mastitis milk

To improve mastitis diagnosis and achieve rapid, specific, reliable and cost effective test, a multiplex PCR for simultaneous detection and differentiation of major streptococcal species, viz. Streptococcus agalactiae, Streptococcus uberis and Streptococcus dysgalactiae was developed. Evaluation with 24 ATCC strains and 606 strains comprising streptococci (84) and staphylococci (522) showed the assay to be highly accurate. The threshold of detection of the mPCR assay was 10fg of genomic DNA and < 102 CFU ml-1. Assessment of 115 milk samples collected from subclinically infected herd, showed mPCR assay to be more efficacious than culture method. Identification of Streptococcus species using this assay will be crucial to determine prevalence of Streptococcus in a herd. This will facilitate early diagnosis, treatment and control of the rate of infection at farm level. The assay can be implemented for routine monitoring of herd health and can be of great value for promoting prevention of streptococcal mastitis.