Streptococcus pyogenes endometritis- a population-based study on the causative emm-types, case clustering and disease severity

PurposeStreptococcus pyogenes is a cause of endometritis, a severe infection in women of reproductive age. S. pyogenes is classified into emm-types based on variations of the emm-gene. We aimed to compare the distribution of emm-types in endometritis to that of controls with bacteraemia, and to assess associations between emm-types and disease severity or clustering of cases.MethodsVaginal or cervical cultures of S. pyogenes from Departments for gynaecology and obstetrics in Skåne, between 2012 and 2020, were identified. Clinical data on patients were retrieved from medical records. Inclusion required an event (childbirth, abortion, miscarriage, intrauterine device insertion or gynaecologic surgery) within 42 days prior to symptom onset. A cluster was defined as ≥ 2 patients with the same emm-type at the same hospital within 14 days. Emm-types of isolates from post-event infections were compared to those of isolates from blood.ResultsA total of 120 patients were identified, 107 had endometritis and 13 had post-event fever. Vaginal delivery was the most common preceding event (79%). Twenty-six patients (22%) fulfilled sepsis criteria, 15 patients required surgical intervention and six were admitted to the ICU. The distribution of emm-types differed significantly between groups (p < 0.001): emm89 was most prevalent in endometritis (21%), whereas emm1 predominated in bacteraemia (33% of 642 isolates). Five suspected clusters involving 12 patients were identified. No significant associations were found between emm-type and disease severity or clustering.ConclusionThe emm-type distribution differed between endometritis and bacteraemia groups, suggesting variation in the propensity of specific emm-types to cause endometritis.