Development of a sensitive polymerase chain reaction assay for group A streptococci

S. pyogenes causes many important human diseases. Rheumatic fever is a systemic inflammatory and nonsuppurative sequla of acute streptococcal pharyngitis that occurs in a small proportion of patients. One hypothesis for the pathogenesis of rheumatic fever was proposed in this thesis, that persistent infection of S. pyogenes in mitral valves is the cause of rheumatic heart disease. A polymerase chain reaction ( PCR ) assay using specific streptococcal primer sets were established and used to determine the sensitivity of different primers for detection of S. pyogenes DNA in human specimens. The PCR assay was used to detect S. pyogenes DNA in mitral valves removed from patients with rheumatic heart disease. The detection of the PCR products from rheumatic heart disease patients matched the history of six out of seven patients using the M-2,3 primer set. DNA sequencing was performed on the PCR products from one rheumatic heart disease patient and S. pyogenes control strain M49. The dot-blot hybridization with different probes was used to identify the homology among the PCR products of rheumatic heart patients and S. pyogenes control strain with M49. Lack of products with two of three sensitive primer sets specific to S. pyogenes DNA and lack of sequence homology with M protein genes by the products obtained with M-2,3 primer set indicated the PCR products from rheumatic heart disease patients was not from S. pyogenes DNA. Thus, no significant evidence supports that persistent infection by S. pyogenes is the cause of rheumatic heart disease occurring many years after an initial rheumatic fever episode.