Streptococcus pyogenes infections with limited emm-type diversity in the homeless population of Brussels, 2016-2018

Objectives: The aim was to characterize the clinical features, outcomes, and strain diversity of laboratory-confirmed Streptococcus pyogenes (group A Streptococcus, GAS) infections among inpatients hospitalized at a tertiary level hospital in Brussels, Belgium, according to the patients' housing status (homeless vs. not homeless). Methods: Between August 2016 and January 2018, all patients hospitalized with a laboratory-confirmed GAS infection were prospectively enrolled and risk factors were recorded. GAS strains were characterized using emm-typing and emm-clustering in both inpatients and outpatients. Analyses were performed according to homelessness status. Results: During the study period, 48% (28/58) of adults hospitalized with a GAS infection at the tertiary hospital were homeless. The estimated incidence rate was 100 times higher for homeless persons. Skin abscesses were more frequent in the homeless group (21.4% vs. 3.3%) and mortality was high (10.7%). Limited emm-type diversity was found in this group, with four emm-types (64, 77, 83, and 101) accounting for 76.1% of the infections, and the majority of these emm-types belonged to the D4 emm-cluster. Pooled analyses of inpatient and outpatient strains indicated lower diversity in the homeless group. Conclusions: The homeless are disproportionately affected by GAS and have a higher rate of abscesses and high mortality. The lower emm-type diversity and preferential infection with four emm-types likely reflects endemic circulation of GAS in this population. Preventive strategies are warranted in this fragile population. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.