INCREASING SEVERITY OF INVASIVE GROUP-A STREPTOCOCCAL DISEASE IN AUSTRALIA - CLINICAL AND MOLECULAR EPIDEMIOLOGIC FEATURES AND IDENTIFICATION OF A NEW VIRULENT M-NONTYPABLE CLONE

We conducted a 12-year review of all cases of group A streptococcal (G AS) bacteremia that were seen at Royal Children's Hospital in Melbourn e, Australia, from 1982 through 1993. Forty-two cases were identified, There was a trend towards increased incidence of infections, as well as a clear increase in their severity, during the study period; more p reviously healthy children were affected during the last 6 years of th e study (80% of cases) than during the first 6 years (47% of cases), a nd more complications occurred during the latter period than during th e former (40% vs, 20%, respectively, with an 88% complication rate ove r the last 12 months). Seventy-four GAS isolates (41 invasive, 23 noni nvasive, and 10 indeterminate) were analyzed. An M type 1 clone that w as positive for the pyrogenic exotoxin A gene (speA) and that has been found to cause invasive disease in the Northern Hemisphere was most f requent among invasive isolates. Molecular typing also identified a ge netically distinct strain that was virulent, mucoid, and M nontypable, Invasive GAS disease in Melbourne has become increasingly aggressive. Newer typing methods should be used in conjunction with traditional s erotyping in order to maintain epidemiological surveillance of virulen t strains.