Molecular epidemiology of community-acquired MRSA (CA-MRSA) and hospital-acquired MRSA (HA-MRSA): sequence types, virulence profiles, and antimicrobial resistance in a Belgian hospital network.

PURPOSE: This study characterizes 109 MRSA isolates collected at a major hospital network in Antwerp, Belgium, focusing on their classification as community-acquired (CA-MRSA) or hospital-acquired (HA-MRSA), antimicrobial susceptibility profiles, genotypic resistance determinants, virulence factors, and sequence type (ST) distribution.

METHODS

This study was conducted retrospectively. MRSA isolates were collected from patients presenting to facilities within the "Ziekenhuis aan de Stroom (ZAS)" hospital network. The strains were prepared for whole genome sequencing with the Nextera XT sample preparation kit (Illumina), followed by sequencing on the Illumina MiSeq platform.

RESULTS

Of the 109 sequenced isolates, 83 (76,1%) were classified as CA-MRSA and 26 (23,9%) as HA-MRSA. Seventy-three (67,0%) isolates originated from clinical samples and 36 (33,0%) from screening samples. MLST revealed substantial genetic diversity. CA-MRSA clinical isolates were most frequently associated with ST5, ST6, ST152, and ST30, whereas HA-MRSA clinical isolates were dominated by ST8. Panton-Valentine leukocidin (PVL) genes were identified in 29 of the 109 isolates (26,6%). Antimicrobial susceptibility differed between CA-MRSA and HA-MRSA and was influenced by sequence type.

CONCLUSION

In this study, the majority of isolates were classified as CA-MRSA based on a pragmatic epidemiological classification. Multiple sequence types (STs) are involved and different STs appear to be associated with varying degrees of clinical severity and virulence genes. Antimicrobial susceptibility profiles are influenced by the circulating ST, which may in turn affect empirical treatment strategies. These findings underscore the need for nationwide surveillance systems for CA-MRSA.