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Comparative Genomic Analysis of Two Serotype 1/2b Listeria monocytogenes Isolates from Analogous Environmental Niches Demonstrates the Influence of Hypervariable Hotspots in Defining Pathogenesis
Casey, Aidan Jordan, Kieran Coffey, Aidan Fox, Edward M. McAuliffe, Olivia
Casey, Aidan
Jordan, Kieran
Coffey, Aidan
Fox, Edward M.
McAuliffe, Olivia
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2016-12-21
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Casey A, Jordan K, Coffey A, Fox EM and McAuliffe O (2016) Comparative Genomic Analysis of Two Serotype 1/2b Listeria monocytogenes Isolates from Analogous Environmental Niches Demonstrates the Influence of Hypervariable Hotspots in Defining Pathogenesis. Front. Nutr. 3:54. doi: 10.3389/fnut.2016.00054
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.