Prevalence and Genetic Diversity of Listeria monocytogenes Isolated From Retail Pork in Wuhan, China

Abstract

Listeria monocytogenes is a ubiquitous bacteria and causative agent of zoonotic listeriosis with high mortality. The consumption of contaminated animal-derived foods has been linked with both epidemic and sporadic listeriosis. In this work, a total of 64 L. monocytogenes isolates from 259 pork samples sold in 11 supermarket chains were identified and characterized by comparative whole-genome analysis. All isolates were delineated into eight clonal complexes (CCs), namely CC2, CC8, CC9, CC11, CC155, CC121, CC204, and CC619, spanning two lineages (I and II) and carrying 3–5 antibiotic-resistant genes (fosX, lnu, mprF, tetM, and dhfR). It is noted that Listeria pathogenicity island (LIPI)-1, LIPI-3, and LIPI-4 were distributed in all ST619 isolates from two supermarket chains that were closely related with clinical isolates (<40 SNP). Some of the isolates from different supermarket chains with 0 SNP difference indicated a common pork supply source. Notably, 57.81% of the strains carried types IB, IIA, or IIIB CRISPR-Cas system, CC121 isolates carried both types IB and IIA CRISPR-Cas systems, Cas proteins of CC155 isolates located between two CRISPR loci, each CC has unique organization of Cas proteins as well as CRISPR loci. CRISPR-Cas system-based subtyping improved discrimination of pork-derived L. monocytogenes isolates. Comparisons at the genome level contributed to understand the genetic diversities and variations among the isolates and provided insights into the genetic makeup and relatedness of these pathogens.

Genetic Diversity and Relationships of Listeria monocytogenes Serogroup IIa Isolated in Poland

“…The remaining seven strains, mainly recovered from RTE food, were grouped into three CCs, with single isolates in each (Figure 1). L. monocytogenes of the CCs identified in the present study were also previously detected among 100 strains of IIa serogroup recovered from food but were also often isolated from humans with listeriosis [12,14,18,[44][45][46][47]. Further analysis of WGS sequences revealed that all 100 current isolates were classified into eight sequence types, with the most prevalent ST155 (33; 33.0%), ST121 (30; 30.0%), and ST8 (28; 28.0%) (Figure 2).…”

“…Three STs (ST8, ST121, and ST155) were identified in L. monocytogenes isolated from all three sources analyzed (Table 1). The results of other authors also showed that ST155 and ST121 were often identified among L. monocytogenes of food origin [14,15,21]. It seems that such isolates may have a molecular background that allows them to survive in food and food production environments in different areas for a long time [11,15].…”

“…Several studies have indicated strains divergence regarding their ability to persist in the environment as well as their virulence potential [ 10 ]. It has been shown that among isolates classified into the evolutionary line II, there are L. monocytogenes of serogroup IIa, which are often over-represented in food and food processing environments; such isolates are usually characterized by a high prevalence of various virulence marker genes and are often identified in humans with listeriosis [ 11 , 12 , 13 , 14 ].…”

Genomic Characterization of Clinical Listeria monocytogenes Isolates in Beijing, China

“…Clinical ST619 isolates were especially specific to China (Wang et al, 2018;Zhang et al, 2019), and harbored the most virulence genes. ST619 isolates carried many virulence genes, including llsX and ptsA that were also found in various food products in China (Wang et al, 2018(Wang et al, , 2021Chen et al, 2019aChen et al, ,b, 2020. However, to date, little information is available on the pathogenicity of ST619 strains, which should be focused on in future studies.…”

Distribution and Characteristics of Listeria spp. in Pigs and Pork Production Chains in Germany

“…in pigs in German slaughterhouses was described by Oswaldi et al [ 18 ]. L. monocytogenes is frequently found in pork products worldwide [ 19 , 20 ], especially in products intended to be eaten raw (ready-to-eat products); this poses a threat to public health [ 21 ]. Some studies have confirmed living pigs as the origin of L. monocytogenes found in pork [ 17 , 22 ]; others identified the slaughter and processing environment as the source of pork contamination [ 23 , 24 ].…”