Group G Streptococcal Necrotizing Soft Tissue Infection: A Pitfall of Rapid Antigen Detection Test for Group A

Necrotizing soft tissue infection (NSTI) caused by group A Streptococcus (GAS) is a life-threatening disease with high morbidity and mortality. Recently, group G Streptococcus (GGS) is increasingly reported as a cause of NSTI, which shows a similar fatality rate. A rapid antigen detection test (RADT) was used for GAS-induced NSTI to assist in the immediate diagnosis when judging the need for debridement surgery.

We describe 2 NSTI cases in which an RADT for GAS was negative, and in which GGS-induced NSTI was subsequently diagnosed. Both cases involved patients over 80 years of age whose medical histories included multiple conditions, including cardiac disorder and lower leg disease. After making a 1-cm skin incision at the central part of erythema, samples for both a wound culture and an RADT for GAS were taken from the subcutaneous layer.

The RADTs were negative; however, the rapidly progressing clinical courses suggested the need for immediate debridement surgeries under general anesthesia. Removal of the skin and subcutaneous tissue and an incision for drainage achieved limb salvage. Wound cultures identified Group G Streptococcus (Streptococcus dysgalactiae) without other bacteria. Negative pressure wound therapy and split-layer mesh skin graft surgery cured the severe wounds without the need for amputation.

Surgeons must be aware of the limitations of the RADT for GAS and determine the appropriate initial treatment based on comprehensive physical and laboratory findings.