Severe infections by S. pyogenes in Spanish pediatric population

In December 2022, an alert was published in the UK and other European countries reporting an unusual increase in the incidence of Streptococcus pyogenes infections. Our aim was to describe the clinical, microbiological, and molecular characteristics of group A Streptococcus invasive infections (iGAS) in children prospectively recruited in Spain (September 2022-March 2023), and compare invasive strains with strains causing mild infections. 130 isolates of S. pyogenes causing infection (102 iGAS and 28 mild infections) were included in the microbiological study: emm typing, antimicrobial susceptibility testing, and sequencing for cgMLST, resistome and virulome analysis. Clinical data were available from 93 cases and 21 controls. Pneumonia was the most frequent clinical syndrome (41/93; 44.1%), followed by deep abscesses (23/93; 24.7%), and osteoarticular infections (11/93; 11.8%). 46/93 cases (49.5%) required admission to the pediatric intensive care unit. iGAS isolates mainly belonged to emm1 and emm12; emm12 predominated in 2022 but was surpassed by emm1 in 2023. Spread of M1UK sublineage (28/64 M1 isolates) was communicated for the first time in Spain, but it did not replace the still predominant sublineage M1global (36/64). Furthermore, a difference in emm types compared with the mild cases were observed with predominance of emm1, but also important representativeness of emm12 and emm89 isolates. Pneumonia, the most frequent and severe iGAS diagnosed, was associated with the speA gene, while the ssa superantigen was associated with milder cases. iGAS isolates were mainly susceptible to antimicrobials. cgMLST showed five major clusters: ST28-ST1357/emm1, ST36-ST425/emm12, ST242/emm12.37, ST39/emm4, and ST101-ST1295/emm89 isolates. Importance Group A Streptococcus (GAS) is a common bacterial pathogen in the pediatric population. In the last months of 2022, an unusual increase in GAS infections was detected in various countries. Certain strains have been overrepresented, although the cause of this outbreak is not clear. In Spain, a significant increase in mild and severe cases was observed; this study evaluated the clinical characteristics and the strains involved in both. Our study showed that the increase in incidence did not correlate with an increase in resistance or with an emmtypes shift. However, there seems to be a rise in severity, in part related to a greater rate of pneumonia diagnosis. These findings suggest a general increase in iGAS that highlightes the need for surveillance. The introduction of whole genome sequencing in the diagnosis and surveillance of iGAS improves the understanding of antibiotic resistance, virulence, and clones, facilitating its control and personalized treatment.