Fatal Streptococcus pyogenes infections in Spain, Turkey, UK and Belgium after pandemics: a comprehensive case series combining microbiology with autopsy findings. A study of the ESCMID study group for forensic and post-mortem microbiology (ESGFOR).

PURPOSE: Invasive Streptococcus pyogenes (iGAS) infections have risen globally since the COVID-19 pandemic. This study aimed to characterize clinical-pathological patterns in iGAS presenting as unexpected deaths and to evaluate the role of post-mortem microbiology alongside clinical and autopsy findings in determining cause of death. METHODS: Anonymized clinical, microbiological, and pathological (macroscopy and/or histopathology) data from fatal cases with positive S. pyogenes cultures, reported in four ESGFOR laboratories between September 2020 and May 2023, were reviewed. RESULTS: Forty cases were identified. Respiratory tract infection (n = 20) and sepsis/septic shock (n = 17) were the most frequent presentations. S. pyogenes was isolated primarily from blood (n = 26) and lung tissue (n = 30). In 37 cases with histopathology, acute inflammation was the predominant feature. S. pyogenes was judged the definite cause of death in 28 cases, contributory in 8, and probable in 2; in two cases, its role remained unclear. The emm-type 1 was strongly associated with the definite cause of death (12/13 cases). CONCLUSION: This study highlights the importance and contribution of post-mortem microbiology and autopsy data in clarifying unexpected/unexplained deaths with a focus on S. pyogenes. Comprehensive autopsy, including post-mortem microbiology and histopathology findings, enabled determination of S. pyogenes’ role in 95% (38/40) of unexpected iGAS deaths. With this type of post-mortem investigation, one may come to new insights for these rapidly progressive and sometimes unexpected fatal infections. Standardized postmortem culture protocols in fatal sepsis cases and a European registry of fatal iGAS may help to better define clinical-pathological patterns of these rapidly progressive and sometimes unexpected fatal infections.