Emergence of Erythromycin- Resistant Invasive Group A Streptococcus, West Virginia, USA, 2020-2021

Clindamycin and beta-lactam antibiotics have been main-stays for treating invasive group A Streptococcus (iGAS) infection, yet such regimens might be limited for strains displaying MLSB phenotypes. We investigated 76 iGAS isolates from 66 patients in West Virginia, USA, during 2020-2021. We performed emm typing using Centers for Disease Control and Prevention guidelines and as-sessed resistance both genotypically and phenotypical-ly. Median patient age was 42 (range 23-86) years. We found 76% of isolates were simultaneously resistant to erythromycin and clindamycin, including all emm92 and emm11 isolates. Macrolide resistance was conferred by the plasmid-borne ermT gene in all emm92 isolates and by chromosomally encoded ermA, ermB, and a single mefA in other emm types. Macrolide-resistant iGAS iso-lates were typically resistant to tetracycline and amino -glycosides. Vulnerability to infection was associated with socioeconomic status. Our results show a predominance of macrolide-resistant isolates and a shift in emm type distribution compared with historical reports.