A. Sharkawy, R. Saginur, D.E. Low, B. Schwartz, K. Green, G. Tyrrell, M. Lovgren, A. McGeer, L. Trpeski. Mount Sinai Hosp., Toronto, Ontario, CANADA; Ottawa Hosp. - Civic Site, Ottawa, Ontario, CANADA; CDC, Atlanta; Natl. Ctr. for Streptococcus, Edmonton, Alberta, CANADA; Univ. of Toronto, Toronto, Ontario, CANADA.

Background/Methods The past decade has witnessed a resurgence of morbidity and mortality due to acute GAS disease. To assess risk factors for and clinical features of GAS STIs, we conducted prospective population-based surveillance for invasive GAS STIs in Ontario from 1992 to 1996. GAS were characterized by M- and T-typing and PCR detection of streptococcal pyrogenic exotoxin genes (speA; speC).

Results Of 1080 cases of invasive GAS disease, 524 were STIs. STI Incidence increased from 0.62 per 100,000 in 1992 to 1.03 in 1996 (p < 0.001). Median age was 47Y (range 1D, 102Y); rates were highest in children and the elderly. Chronic underlying illness was noted in 237 cases (50%). Incidence of invasive soft tissue disease was significantly higher in the setting of diabetes (RR 6.5, P<0.001), alcoholism (RR 3.1, P<0.001), cancer (RR 3.9, P<0.001), cardiac (2.7, P<0.001) and pulmonary (RR 4.0, P<0.001) disease. Severe sepsis complicated 64 cases (12%) and necrotizing fasciitis (NF) 118 (23%). The case fatality rate was 13% (68/520), but was 26% in those 64 or older, 23% amongst those with underlying illness, 27% in NF and 49% in severe sepsis. No deaths occurred in patients without NF or chronic underlying illness. The most common serotypes were M1 (24%) and M3 (9%). In multivariable analysis, NF was associated with M1 and M3 types, absence of cancer, and infection at sites other than head and neck; severe sepsis was associated with M3 type, underlying illness, and infections at sites of lymphatic drainage.

Conclusions The incidence of invasive GAS STI in Ontario increased significantly between 1992 and 1996. Diabetics are particularly predisposed. Patients without chronic underlying illness and those who do not develop NF can be considered for outpatient management.

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