Journal
MICROORGANISMS
Volume 9, Issue 2, Pages -Publisher
MDPI
DOI: 10.3390/microorganisms9020376
Keywords
Listeria monocytogenes; persistent clusters; biofilm; environmental stresses resistance; QAC-resistance; hypo-virulent clones; hyper-virulent clones; WGS; bioinformatics analysis
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Funding
- Italian Ministry of Health (Progetto di Ricerca Corrente) [IZSUM RC 006/2017]
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A study was conducted on 66 Listeria monocytogenes (Lm) strains isolated from a small-scale meat processing plant and a dairy facility in Central Italy from 2013 to 2018. Whole Genome Sequencing and bioinformatics analysis revealed genetic relationships between the strains, persistence, and virulence abilities. The study found that CC9 and CC121 strains in the meat processing plant were more adapted to the environment and showed higher biofilm production, while the CC2 strains in the dairy facility persisted for a longer period of time.
A total of 66 Listeria monocytogenes (Lm) isolated from 2013 to 2018 in a small-scale meat processing plant and a dairy facility of Central Italy were studied. Whole Genome Sequencing and bioinformatics analysis were used to assess the genetic relationships between the strains and investigate persistence and virulence abilities. The biofilm forming-ability was assessed in vitro. Cluster analysis grouped the Lm from the meat plant into three main clusters: two of them, both belonging to CC9, persisted for years in the plant and one (CC121) was isolated in the last year of sampling. In the dairy facility, all the strains grouped in a CC2 four-year persistent cluster. All the studied strains carried multidrug efflux-pumps genetic determinants (sugE, mdrl, lde, norM, mepA). CC121 also harbored the Tn6188 specific for tolerance to Benzalkonium Chloride. Only CC9 and CC121 carried a Stress Survival Islet and presented high-level cadmium resistance genes (cadA1C1) carried by different plasmids. They showed a greater biofilm production when compared with CC2. All the CC2 carried a full-length inlA while CC9 and CC121 presented a Premature Stop Codon mutation correlated with less virulence. The hypo-virulent clones CC9 and CC121 appeared the most adapted to food-processing environments; however, even the hyper-virulent clone CC2 warningly persisted for a long time. The identification of the main mechanisms promoting Lm persistence in a specific food processing plant is important to provide recommendations to Food Business Operators (FBOs) in order to remove or reduce resident Lm.
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