Abstract
Listeria species may colonize and persist in food processing facilities for prolonged periods of time, despite hygiene interventions in place. To understand the genetic factors contributing to persistence of Listeria strains, this study undertook a comparative analysis of seven persistent and six presumed non-persistent strains, isolated from a single food processing environment, to identify genetic markers correlating to promoting persistence of Listeria strains, through whole genome sequence analysis. A diverse pool of genetic markers relevant to hygiene tolerance was identified, including disinfectant resistance markers qacH, emrC and the efflux cassette bcrABC. Both persistent and presumed non-persistent cohorts encoded a range of stress resistance markers, including heavy metal resistance, oxidative and pH stress, although trends were associated with each cohort (e.g., qacH and cadA1C resistance was more frequently found in persistent isolates). Persistent isolates were more likely to contain mutations associated with attenuated virulence, including a truncated InlA. Plasmids and transposons were widespread between cohorts. Results suggest that no single genetic marker identified was universally responsible for a strain's ability to persist. Persistent strains were more likely to harbour mutation associated with hypovirulence. This study provides additional insights into the distribution of genetic elements relevant to persistence across Listeria species, as well as strain virulence potential.
Highlights
Listeria species comprise an expanding genus of bacteria, which to date includes 21 recorded species, many of which are relatively recently described (Leclercq et al 2019; Quereda et al 2020)
Listeria monocytogenes is of primary concern to public health, Listeria ivanovii is an important pathogen of animals (Orsi and Wiedmann 2016)
Listeria monocytogenes shared a greater number of genes exclusively with L. innocua (n = 477), relative to genes exclusive with L. welshimeri (n = 178); this is supported by the likelihood of these species being closer in evolutionary terms (Orsi and Wiedmann 2016)
Summary
Listeria species comprise an expanding genus of bacteria, which to date includes 21 recorded species, many of which are relatively recently described (Leclercq et al 2019; Quereda et al 2020) Of these species, Listeria monocytogenes is of primary concern to public health, Listeria ivanovii is an important pathogen of animals (Orsi and Wiedmann 2016). Listeria monocytogenes is of primary concern to public health, Listeria ivanovii is an important pathogen of animals (Orsi and Wiedmann 2016) These bacteria can be found ubiquitously in the environment and may contaminate foods including ready-to-eat foods, vegetable, seafood, meat, eggs and dairy products; incidence of disease is mainly linked to infections via foodborne transmission (Fugett et al 2007; Scallan et al 2011; McAuley et al 2014). This includes the use of antimicrobial agents such as quaternary ammonium compounds (QACs), as well as other antimicrobial formulations
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