Small-fragment restriction endonuclease analysis in epidemiological mapping of group A streptococci.

The usefulness of small-fragment restriction endonuclease digest analysis (SF-REA) of group A streptococcal DNA with EcoRI, as a supplement to the more conventional T serotyping, was assessed for epidemiological 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 serotyping. Generally, there was a striking correlation between the results obtained with the two techniques. Furthermore, SF-REA reliably classified the eight T-non-typable isolates and occasionally revealed subgroups within the T serotypes. In addition, SF-REA was useful for the clarification of discrepancies between serotyping results from two different reference laboratories. No obvious correlation was observed between the DNA fingerprints and the clinical manifestations of infection or the geographical origin of the group A streptococcal isolates. SF-REA is a valuable supplement to T typing in epidemiological studies and frequently appears to be a more efficient tool for strain differentiation.