SMALL-FRAGMENT RESTRICTION-ENDONUCLEASE ANALYSIS IN EPIDEMIOLOGIC MAPPING OF GROUP-A STREPTOCOCCI

The usefulness of small-fragment restriction endonuclease digest analy sis (SF-REA) of group A streptococcal DNA with EcoRI, as a supplement to the more conventional T serotyping, was assessed for epidemiologica l characterisation. One hundred and thirty-five clinical isolates from 1988-1990 were examined. SF-REA provided characteristic fingerprints of all isolates, whereas eight isolates were non-typable by T serotypi ng. Generally, there was a striking correlation between the results ob tained with the two techniques, Furthermore, SF-REA reliably classifie d the eight T-non-typable isolates and occasionally revealed subgroups within the T serotypes. In addition, SF-REA was useful for the clarif ication of discrepancies between serotyping results from two different reference laboratories. No obvious correlation was observed between t he DNA fingerprints and the clinical manifestations of infection or th e geographical origin of the group A streptococcal isolates. SF-REA is a valuable supplement to T typing in epidemiological studies and freq uently appears to be a more efficient tool for strain differentiation.