Occurrence and Genomic Characterization of Listeria monocytogenes ST121 in Animal-Derived Food Samples from Bejaïa,...

Listeria monocytogenesis an important foodborne pathogen that can cause severe invasive disease in vulnerable populations. This study assessed the occurrence of L. monocytogenes in animal-derived foods collected in Bejaïa, Algeria, and characterized recovered isolates using whole-genome sequencing (WGS). A total of 553 samples (red meat, minced meat, sausage, chicken carcasses, raw milk, and artisanal butter) were analyzed using ISO 11290-based culture, with species confirmation by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Twenty-two isolates were recovered (overall prevalence 4% ± 1.6), with the highest positivity in chicken carcasses (10.9% ± 5.8, 12/110) and artisanal butter (12.5% ± 16.2, 2/16). All isolates belonged to sequence type ST121 and carried the same plasmid replicon rep26. No acquired antimicrobial resistance genes were identified in any isolate. Screening of virulence-associated loci indicated genomic carriage of all conserved set of loci. A truncation in inlA gene was present, which has been associated with decreased virulence pattern. These findings highlight the occurrence of L. monocytogenes in multiple animal-derived products in Bejaïa and support the integration of WGS into routine food-chain surveillance.