Comparative Genomic Analysis of Two Serotype 1/2b Listeria monocytogenes Isolates from Analogous Environmental Niches Demonstrates the Influence of Hypervariable Hotspots in Defining Pathogenesis

Abstract

The vast majority of clinical human listeriosis cases are caused by serotype 1/2a, 1/2b, 1/2c, and 4b isolates of Listeria monocytogenes. The ability of L. monocytogenes to establish a systemic listeriosis infection within a host organism relies on a combination of genes that are involved in cell recognition, internalization, evasion of host defenses, and in vitro survival and growth. Recently, whole genome sequencing and comparative genomic analysis have proven to be powerful tools for the identification of these virulence-associated genes in L. monocytogenes. In this study, two serotype 1/2b strains of L. monocytogenes with analogous isolation sources, but differing infection abilities, were subjected to comparative genomic analysis. The results from this comparison highlight the importance of accessory genes (genes that are not part of the conserved core genome) in L. monocytogenes pathogenesis. In addition, a number of factors, which may account for the perceived inability of one of the strains to establish a systemic infection within its host, have been identified. These factors include the notable absence of the Listeria pathogenicity island 3 and the stress survival islet, of which the latter has been demonstrated to enhance the survival ability of L. monocytogenes during its passage through the host intestinal tract, leading to a higher infection rate. The findings from this research demonstrate the influence of hypervariable hotspots in defining the physiological characteristics of a L. monocytogenes strain and indicate that the emergence of a non-pathogenic isolate of L. monocytogenes may result from a cumulative loss of functionality rather than by a single isolated genetic event.

Antimicrobial susceptibility patterns of Listeria monocytogenes isolated from fresh produce in KwaZulu-Natal Province, South Africa

“…This finding supports previous studies that identified the presence of internalin genes in L. monocytogenes isolates from irrigation water and agricultural soil in South Africa's Eastern Cape Province (Iwu et al, 2022). Moreover, the inlA gene has long been known to be conserved in L. monocytogenes (Poyart et al, 1996), and has been implicated in the establishment of listeriosis (Chatterjee, 2006;Ingeborg, 2011;Casey et al, 2016). The surface internalin A (inlA) protein, a product of the inlA gene, plays an important role in the invasion of L. monocytogenes into mammalian cells (Werbrouck et al, 2006;Phelps et al, 2018).…”

Assessment of multidrug-resistant Listeria monocytogenes in milk and milk product and One Health perspective

“…Listeriosis outbreak involving serotype 1/2b from cheese has also been reported [ 53 ]. Also, serotype 1/2b has been found in cases of bovine mastitis [ 54 ]. The presence of these serotypes in dairy samples suggest that they could constitute a potential health threat to consumers.…”

Validation of Predicted Virulence Factors in Listeria monocytogenes Identified Using Comparative Genomics

“…Comparative genomic analyses of L. monocytogenes strain EGD-e with nonpathogenic L. innocua strain CLIP1182 revealed potential genetic differences responsible for pathogenicity [23]. Since then, several virulence factors were identified in L. monocytogenes by comparative genomics [12,24]. In the current study, we assessed the contribution to virulence of five L. monocytogenes genes identified solely by comparative genomics.…”