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

Abstract 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.