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

Abstract

Clindamycin and β-lactam antibiotics have been mainstays 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 assessed resistance both genotypically and phenotypically. 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 isolates were typically resistant to tetracycline and aminoglycosides. 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.

Keywords

• invasive group A Streptococcus
• antimicrobial resistance
• streptococci
• Streptococcus pyogenes
• erythromycin
• clindamycin