Non-Necrotizing Soft Tissue Infection and Streptococcal Toxic Shock Syndrome Caused by a Novel Streptococcus pyogenes Subtype (emm76.10).

We report a case of non-necrotizing soft tissue infection and streptococcal toxic shock syndrome (STSS) caused by a novel emm subtype (emm76.10) of group A Streptococcus pyogenes (GAS). A 54-year-old Japanese woman suffering from fever, fatigue, and lower abdominal pain along with erythema for 3 days was admitted to our hospital. Additionally, she presented with hypotension and multiple organ failure. Exploratory incision was performed due to the presence of STSS and for an examination of the necrotizing soft tissue infection from her lower abdomen to the left thigh. Tissue cultures from the exudates and fascia yielded positive results for GAS growth, although blood cultures returned as negative. After 15 days of antimicrobial therapy, she recovered fully without any complications. Genotyping of the isolate indicated a novel emm subtype (emm76.10), with 5 amino acid substitutions in the emm76.0 subtype sequence and the full-length sequence of 780 bp. This isolate was resistant to tetracyclines, macrolides-lincosamides, and fluoroquinolones, owing to the presence of antibiotic resistance determinants, tet(M) and erm(B), and point mutations, Ser79Phe/Ser81Phe, in the quinolone resistance-determining regions of parC/gyrA. In conclusion, our observations suggest the importance of early-stage exploratory incision and drainage from the infected region for the isolation and characterization of causative bacteria to facilitate selection of appropriate antibiotics for treatment.