Population-Based Surveillance for Group A Streptococcal Necrotizing Fasciitis: Clinical Features, Prognostic Indicators, and Microbiologic Analysis of Seventy-Seven Cases

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Abstract

PURPOSE: To determine the incidence of group A streptococcal necrotizing fasciitis in Ontario, Canada, and to describe the clinical features, outcome, and microbiologic characteristics of this infection.

PATIENTS AND METHODS: Prospective, population-based surveillance for invasive group A streptococcal infections was conducted in Ontario from November 1991 to May 1995. All 77 patients meeting clinical and/or histopathologic criteria for streptococcal necrotizing fasciitis were included. Demographic and clinical information was obtained by patient interviews and chart review. Group A streptococci were characterized by M-protein and T-agglutination typing, and polymerase chain reaction (PCR) detection of streptococcal pyrogenic exotoxin genes A and C (speA; speC).

RESULTS: The incidence of group A streptococcal necrotizing fasciitis increased during the study from 0.085 per 100,000 population in the first year to 0.40 per 100,000 population in the last year (P <0.001). The median age of cases was 57.5 years and the rate of disease increased with increasing age. Seventy-nine percent of cases were community-acquired, 11% were nosocomial, and 10% were acquired in a nursing home. Forty-seven percent of cases were associated with the presence of streptococcal toxic shock syndrome (Strep TSS) and 46% were bacteremic. Thirty-four percent of cases died and mortality was correlated with increasing age (P = 0.006), presence of hypotension (P = 0.01), and bacteremia (P = 0.03). The most common streptococcal serotypes were M1 (35%) and M3 (25%). Forty-one percent of strains possessed the speA gene and 30% the speC gene. Outcome was not correlated with M-type or the presence of spe genes.

CONCLUSIONS: The incidence of necrotizing fasciitis caused by group A streptococcus increased in Ontario between 1992 and 1995. Elderly individuals were more likely to acquire the disease and to die from it. Mortality because of streptococcal necrotizing fasciitis was also associated with the presence of hypotension, Strep TSS, or bacteremia, but not with M-type or the presence of pyrogenic exotoxin genes.

Section snippets

Patients

Active, population-based surveillance of group A streptococcal infections in Ontario, Canada (population 10.9 million in 1994)[16]has been conducted by our group since November 1991 for necrotizing fasciitis, and since January 1992 for all invasive disease.[17]All microbiology laboratories serving Ontario hospitals notified the study office whenever group A streptococcus was isolated from specimens other than throat or eye swabs. Attending physicians were then contacted to determine whether the

Patient Characteristics

Seventy-seven cases of group A streptococcal necrotizing fasciitis were identified between November 1991 and May 1995. The incidence of disease increased during this time period from a rate of 0.085 per 100,000 population in the first 12 months of surveillance to 0.40 per 100,000 population in the last 12 months (P <0.001). Cases occurred more often in the winter months; 61% of cases occurred between December and March (P <0.001). The rate of disease increased with increasing age, with annual

Discussion

The most severe form of soft tissue infection caused by group A Streptococcus is necrotizing fasciitis, characterized by necrosis and inflammation of fascia and subcutaneous tissues. Previous reports of this disease have included case reports and retrospective reviews involving relatively small numbers of cases.13, 14, 15, 24, 25, 26Using stringent diagnostic criteria, the cases herein described represent the largest series of group A streptococcal necrotizing fasciitis reported to date, and

Acknowledgements

Supported in part by grants from the Centers for Disease Control and Prevention, Atlanta, Georgia, USA, (CDC Contract No. 200-91-0929); Canadian Bacterial Diseases Network; and M.D.S. Health Group Limited, Toronto, Ontario, Canada.

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