Whole genome characterization of Listeria welshimeri isolates recovered from cattle abattoirs and retailers in Gauteng province in South Africa

Abstract

The study used whole-genome sequencing (WGS) to characterize 12 isolates of L. welshimeri recovered from the beef production chain in Gauteng province, South Africa. Two sequence types (STs) were identified, with ST3294 accounting for 75% (9/12) and ST1084 for 16.7% (2/12) of the isolates. Antimicrobial resistance (AMR) plasmids detected included conjugative plasmid (MOBP2; T_virB11; virb4) in 58.3% and AMR plasmid (NFO33156) in 41.7% of the isolates. Two AMR genes, fosX (25%) and vga (G) (100%), along with 11 virulence factors, were present in all 12 isolates of L. welshimeri. The phylogenomic tree of L. welshimeri clustering based on the ST according to the source, type, and class of beef and beef products revealed three groups: ST3294 (n = 9), ST1084 (n = 2), and unassigned ST (n = 1). The findings of this study demonstrate the potential for transferring genetic materials from non-pathogenic L. welshimeri to pathogenic L. monocytogenes within the same ecological niche.