The Slaughterhouse as Hotspot of CC1 and CC6 Listeria monocytogenes Strains with Hypervirulent Profiles in an Integrated Poultry Chain of Italy

Abstract

In Europe, very few studies are available regarding the diversity of Listeria monocytogenes (L. monocytogenes) clonal complexes (CCs) and sequence types (ST) in poultry and on the related typing of isolates using whole genome sequencing (WGS). In this study, we used a WGS approach to type 122 L. monocytogenes strains isolated from chicken neck skin samples collected in two different slaughterhouses of an integrated Italian poultry company. The studied strains were classified into five CCs: CC1-ST1 (21.3%), CC6-ST6 (22.9%), CC9-ST9 (44.2%), CC121-ST121 (10.6%) and CC193-ST193 (0.8%). CC1 and CC6 strains presented a virulence gene profile composed of 60 virulence genes and including the Listeria Pathogenicity Island 3, aut_IVb, gltA and gltB. According to cgMLST and SNPs analysis, long-term persistent clusters belonging to CC1 and CC6 were found in one of the two slaughterhouses. The reasons mediating the persistence of these CCs (up to 20 months) remain to be elucidated, and may involve the presence and the expression of stress response and environmental adaptation genes including heavy metals resistance genes (cadAC, arsBC, CsoR-copA-copZ), multidrug efflux pumps (mrpABCEF, EmrB, mepA, bmrA, bmr3, norm), cold-shock tolerance (cspD) and biofilm-formation determinants (lmo0673, lmo2504, luxS, recO). These findings indicated a serious risk of poultry finished products contamination with hypervirulent L. monocytogenes clones and raised concern for the consumer health. In addition to the AMR genes norB, mprF, lin and fosX, ubiquitous in L. monocytogenes strains, we also identified parC for quinolones, msrA for macrolides and tetA for tetracyclines. Although the phenotypical expression of these AMR genes was not tested, none of them is known to confer resistance to the primary antibiotics used to treat listeriosis The obtained results increase the data on the L. monocytogenes clones circulating in Italy and in particular in the poultry chain.

Characterization of Listeria monocytogenes Strains Isolated in Palermo (Sicily and Italy) during the Years 2018–2020 from Severe Cases of Listeriosis

“…Moreover, our study revealed the presence of a hypervirulent strain, ST6/VT19, associated with several epidemic outbreaks, particularly in Europe in 2015-2020, showing a wide and intercontinental diffusion [39]. Indeed, due to the worldwide commercialization of food products, hypervirulent strains spread rapidly over large geographic areas, causing multi-country outbreaks.…”

Foodborne bacteria in slaughterhouses : with focus on cleaning and disinfection

“…This poses significant concerns for food business operators (FBOs), as it can lead to outbreaks due to crosscontamination when food products come into contact with inadequately cleaned surfaces. A recent study detected hypervirulent L. monocytogenes strains in slaughterhouses (Guidi et al 2023), which is a particularly important finding as there is an increasing trend in listeriosis cases in Sweden (Figure 3).…”

Transmission of bla NDM in Enterobacteriaceae among animals, food and human

“…NDM-CRE exhibited a significant increase in detection rate within the livestock production chain, in which the slaughterhouses are the hotspots for cross-contamination of NDM-CRE. Slaughterhouse was proved to play a significant role in the contamination and dissemination of various pathogens including Salmonella [ 33 ], Listeria monocytogenes [ 34 ] and particularly the antimicrobial resistance (AMR) strains [ 35 ]. Here, in this study, although NDM-negative isolates presented in NDM-free chicken and pig farms, the livestock from these NDM-free farms are transported to the slaughterhouses, where the livestock from NDM-positive farms entered and slaughtered as well, cross-contaminated with NDM-CRE in meat processing.…”