Bert Bogaerts, Carole Kowalewicz, Sigrid C J De Keersmaecker, Nancy H C Roosens, Kevin Vanneste, Cécile Boland
Five sequence types (STs) were identified: ST1 (n = 1), ST22 (n = 6), ST80 (n = 1), ST239 (n = 8), and ST612 (n = 1), all belonging to clonal complexes other than the typical livestock-associated CC398. For ST22 and ST239, we identified several isolates that showed very high genomic similarity, indicating either transmission between farms or acquisition from a common source. For ST239, we identified a shared lineage among isolates collected from laying hens and cattle throughout the study period. A comparison with public datasets revealed a high genomic similarity between the isolates from this study and globally circulating human-associated lineages, suggesting shared ancestry and clonal spread rather than direct evidence of zoonotic transmission.
INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen resistant to several widely used antibiotics. Although MRSA has historically been associated with hospital- and community-associated infections, livestock-associated MRSA (LA-MRSA) has emerged as a public health concern worldwide. While the majority of studies on LA-MRSA have focused on the CC398 lineage, little is known about the other lineages circulating in livestock. This study reports the whole-genome sequencing (WGS)-based characterization of 17 non-CC398 MRSA isolates with spa types typically associated with human infections.
METHODS: The isolates were collected from healthy food-producing farm animals in Belgium between 2011 and 2021. WGS was used for typing and detecting antimicrobial resistance (AMR), virulence genes, and plasmids. Core genome multi-locus sequence typing (MLST) and single nucleotide polymorphism (SNP)-based phylogenomic analyses were performed to investigate the relationship between isolates and to compare them with publicly available genomic data.
RESULTS: Five sequence types (STs) were identified: ST1 (n = 1), ST22 (n = 6), ST80 (n = 1), ST239 (n = 8), and ST612 (n = 1), all belonging to clonal complexes other than the typical livestock-associated CC398. For ST22 and ST239, we identified several isolates that showed very high genomic similarity, indicating either transmission between farms or acquisition from a common source. For ST239, we identified a shared lineage among isolates collected from laying hens and cattle throughout the study period. A comparison with public datasets revealed a high genomic similarity between the isolates from this study and globally circulating human-associated lineages, suggesting shared ancestry and clonal spread rather than direct evidence of zoonotic transmission.
DISCUSSION: This study provides insights into the genomic diversity, spread, and potential public health relevance of non-CC398 MRSA lineages circulating in Belgian livestock.