# Streptococcus dysgalactiae as a cause of peripartum infections - a population-based cohort study with phylogenetic analysis of hospital clusters

## TL;DR

This study examines how often Streptococcus dysgalactiae causes infections after childbirth and finds that while serious cases are rare, the infections are common and can spread in hospitals.

## Contribution

The study provides population-based evidence on S. dysgalactiae peripartum infections and uses phylogenetic analysis to assess hospital cluster outbreaks.

## Key findings

- S. dysgalactiae peripartum infections affect about 1 in 1000 births.
- Hospital clusters of these infections are rare, but whole genome sequencing is recommended to confirm relatedness.
- The most common emm-type identified was stG62647.

## Abstract

We aimed to investigate the incidence and clinical features of Streptococcus dysgalactiae peripartum infections (SDPI), and to investigate the distribution of emm-types in relation to disease severity and the genetic relatedness of isolates from hospital clusters.

Patients with growth of S. dysgalactiae in a genital or wound culture, collected between January 2014 and September 2020 at departments for gynecology and obstetrics, were identified. For inclusion, patients had to be pregnant, or given birth, or undergone an abortion within 42 days prior to debut of symptoms. All isolates had previously been emm-typed. A cluster was defined as two or more patients with S. dysgalactiae of the same emm-type admitted to the same hospital within a 30-day period. The cluster isolates were subjected to whole genome sequencing (WGS).

The final study cohort comprised 130 patients. The incidence of S. dysgalactiae postpartum infection was approximately 1 case/1000 births. The patients fulfilled criteria for endometritis (n = 94), postpartum fever (n = 15), wound infection (n = 8) or chorioamnionitis (n = 4). Most patients with endometritis (87%) had onset of symptoms > 48 h post-partum. The most common emm-type was stG62647 (n = 41). Thirteen hospital clusters were identified, of which only three had bacterial isolates that were closely genetically related (0–6 SNP).

Our findings demonstrate that SDPI impact a relatively large number of patients. No patient was critically ill, but the morbidity appeared to be substantial. Hospital outbreaks of SDPI are rare, but when suspected, WGS should be employed to investigate relatedness between isolates.