Whole-genome sequencing-based characterization of listeria monocytogenes from food and animal clinical cases

Listeriosis is a rare but severe foodborne infection caused by Listeria monocytogenes. In this study, we performed comparative whole-genome sequencing (WGS) on 28 Listeria monocytogenes from seven invasive listeriosis cases in animals and 21 food samples in Türkiye for the first time. Food isolates were delineated into eleven clonal complexes (CCs), namely CC1, CC2, CC3, CC8, CC9, CC20, CC69, CC124, CC155, CC204, ST3002. The isolates from meningoencephalitis cases were associated with CC1, whereas CC9 and CC7 were associated with the isolates from sheep abortus cases. All the isolates carried the fosX, lin, norB, and sul genes. In addition, emrC (n=15), bcrC (n=4), emrE (n=2), qacA (n=1), cadA (n=5) and cadC (n=1) genes, conferring resistance to stress and disinfectants were detected. Listeria pathogenicity island (LIPI)-1 and LIPI-2 were distributed in all isolates, but LIPI-3 was closely related to CC1, CC3, and ST3002 isolates. LIPI-4 was not found in any of the L. monocytogenes isolates. The Inc18(rep25) and Inc18(rep26) plasmids were found in 16 (57.1%) isolates. A total of 15 different intact prophage genomes ranging from one to three were detected in the genomes of 24 isolates. The hypervirulent CC1 and CC2 clones that pose a significant threat to food safety and public health were detected among food isolates. These findings highlight the importance of continuous surveillance of hypervirulent L. monocytogenes strains in different settings.