Outbreak of group A streptococci in a burn center: use of pheno- and genotypic procedures for strain tracking

Abstract

In a burn center, an outbreak of group A streptococci (GAS) colonizations involving 13 patients and two staff members occurred. Adverse events due to GAS, loss of skin graft after initial take (secondary loss) and partial take, occurred in patients who underwent surgery before the colonization was detected. GAS isolates from nine patients and one staff member were stored and subsequently pheno- and genotyped by T serotyping, gas chromatography, M genotyping, and random amplified polymorphic DNA typing. The outbreak was caused by two types of GAS, identified as T4/28-M48 and T13-M77 by T serotyping and M genotyping. Random amplified polymorphic DNA typing and gas chromatography distinguished both clusters accurately. One subcluster indicated by gas chromatography could be linked to the acquisition of GAS from a roommate. The T13-M77 cluster was characterized by rapid spread through the center compared with the T4/28-M48 cluster. One patient contracted the T13-M77 strain while in protective isolation, indicating a role for staff members in the transmission. Our standard GAS control policy, consisting of twice weekly screening of all burned patients and immediate isolation and treatment, proved efficacious in preventing further spread of GAS. Reporting by staff members of signs and symptoms compatible with GAS infection was reenforced.