Clinical and molecular characteristics of invasive and noninvasive skin and soft tissue infections caused by group A Streptococcus.

The severity of skin and soft tissue infections caused by group A Streptococcus (GAS) is variable, and there are only a limited number of studies evaluating the characteristics of these infections in the literature. From May 2005 to November 2007, 73 patients with skin and soft tissue infections caused by group A Streptococcus were included in this study. Among these patients, 34 (46.6%) had invasive diseases. Diabetes mellitus, alcoholism, and hypertension were the most common underlying disorders. The overall mortality rate was 6.8%, and the elderly were predisposed to invasive infections (P < 0.001). Neutrophil percentages of ≥80, serum creatinine levels of ≥2 mg/dl, and high serum C-reactive protein levels were noted more frequently in patients with invasive infections than in patients with noninvasive infections, as were bacteremia and a high mortality rate. Of the 73 isolates, 93.2%, 97.3%, and 37% exhibited susceptibility to erythromycin, clindamycin, and tetracycline, respectively. The five most prevalent emm types were emm106 (24.7%), emm11 (12.3%), emm102 (9.6%), emm4 (8.2%), and emm12 (8.2%). Compared to other types, the emm106 type was significantly more likely to be associated with invasive diseases (P = 0.012). Dendrogram analysis showed a unique SmaI-digested pulsed-field gel electrophoresis pattern of the emm106 type that was particularly prone to cause invasive skin and soft tissue infections (P < 0.001). The results of this study suggest that isolates with the emm106 gene may be an emerging group A Streptococcus strain that causes invasive skin and soft tissue infections. Further surveillance study to understand the significance of this invasive strain is critical.