Impact of the COVID-19 Pandemic on Group A Streptococcal Necrotizing Soft Tissue Infections: A Retrospective Cohort Study

Background Necrotizing soft tissue infections (NSTIs) are often caused by group A Streptococcus (GAS). As the number of invasive GAS infections decreased during the coronavirus disease 2019 (COVID-19) pandemic restrictions, this study aimed to compare the occurrence of GAS-NSTIs before, during, and after the COVID-19 pandemic restrictions. Methods This retrospective cohort study included adult patients with NSTIs admitted to the intensive care unit (ICU) of the University Hospital Zurich, Switzerland, from July 2008 to December 2023. NSTI cases were categorized as pre-, during, and postrestrictions. The primary outcome was the proportion of GAS in NSTI, and the exploratory secondary outcome was in-hospital death. A data analysis was conducted using Firth logistic regression adjusted for age, sex, diabetes, and initially affected body region. Results Overall, 74 NSTI cases were identified, with 49 occurring before, 8 during, and 17 after the pandemic restrictions. GAS was isolated in 27 (36%) cases, with 17 (35%) pre- and 10 (59%) postrestrictions, but none during the restrictions. NSTIs caused by other bacteria persisted during the restrictions. The odds of GAS were significantly lower during the restrictions (adjusted odds ratio, 0.02; 95% CI, 0.001–0.81) compared with after, while no significant differences were found between the pre- and postrestriction periods. Conclusions The significant decrease of GAS-NSTIs during the COVID-19 pandemic restrictions suggests that isolation measures may have prevented the transmission of GAS, resulting in a decline of GAS-NSTIs while NSTIs caused by bacteria transmitted by alternative routes persisted

Molecular epidemiology of invasive Group A streptococcal infections before and after the COVID-19 pandemic in Switzerland

Group A Streptococcus (GAS, aka Streptococcus pyogenes) poses a significant public health concern, causing a diverse spectrum of infections with high mortality rates. Following the COVID-19 pandemic, a resurgence of invasive GAS (iGAS) infections has been documented, necessitating efficient outbreak detection methods. Whole genome sequencing (WGS) serves as the gold standard for GAS molecular typing, albeit constrained by time and costs. This study aimed to characterize the post-pandemic increased prevalence of iGAS on the molecular epidemiological level in order to assess whether new, more virulent variants have emerged. A total of 66 iGAS strains isolated from nine Swiss hospitals during the COVID-19 post-pandemic increased GAS prevalence were evaluated and compared to 15 strains collected before and 12 during the COVID-19 pandemic. FT-IR measurements and WGS were conducted for network analysis. Demographic, clinical, and epidemiological data were collected. Skin and soft tissue infection was the most common diagnosis, followed by primary bacteremia and pneumonia. Viral co-infections were found in 25% of cases and were significantly associated with more severe disease requiring intensive care unit admission. WGS analysis did not reveal emerging GAS genetic distinct variants after the COVID-19 pandemic, indicating the absence of a pandemic-induced shift. FT-IR spectroscopy exhibited limitations in differentiating genetically distant GAS strains, yielding poor overlap with WGS-derived clusters. The emm1/ST28 genotype was predominant in our cohort and was associated with five of the seven deaths recorded, in accordance with the molecular epidemiological data before the pandemic. Additionally, no notable shift in antibiotic susceptibility patterns was observed. Our data suggest that mainly non-pathogen related factors contributed to the recent increased prevalence of iGAS