Temporal trends in Group A Streptococcus epidemiology, antimicrobial susceptibility and emm-type distribution: a...

Group A Streptococcus (GAS) remains universally susceptible to penicillin; however, resistance to macrolides and clindamycin varies geographically and may affect management, particularly in patients with penicillin allergy. Recent increases in GAS incidence reported in the United Kingdom highlight the need for continued local epidemiological and antimicrobial resistance surveillance.

We conducted a retrospective laboratory-based surveillance study at a UK district general hospital between January 2017 and December 2023. All laboratory-confirmed GAS isolates were included. Isolates were classified as invasive or non-invasive based on specimen source. Antimicrobial susceptibility testing was performed using European Committee on Antimicrobial Susceptibility Testing (EUCAST) methodology, and emm typing was undertaken for available invasive isolates. Data were analysed descriptively to assess temporal trends across pre-pandemic, pandemic and post-pandemic periods.

A total of 2,893 GAS isolates were identified, including 45 invasive isolates (1.6%). GAS activity demonstrated marked temporal variation during the seven-year surveillance period, with substantial suppression during 2020-2021 followed by a marked increase in 2022-2023, exceeding pre-pandemic levels. Throat swab specimens accounted for the largest proportion of isolates (59.0%), followed by wound specimens (22.8%) and genital specimens (12.4%). Penicillin susceptibility remained universal throughout the study period. Erythromycin and clindamycin susceptibility demonstrated temporal variation, with the lowest susceptibility observed in 2021 before recovery in subsequent years. Tetracycline susceptibility remained relatively stable. Among typed invasive isolates (29/45), emm1 was the predominant emm type (48.3%).

GAS activity demonstrated marked temporal variation, with a substantial increase following the COVID-19 pandemic. Despite this, antimicrobial susceptibility patterns remained largely stable, with universal penicillin susceptibility. Variability in macrolide and clindamycin susceptibility highlights the importance of ongoing surveillance to inform empirical therapy, particularly in penicillin-allergic patients. The predominance of emm1 among invasive isolates aligns with national trends and supports continued molecular surveillance.