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Stress survival islet 1 contributes to serotype‐specific differences in biofilm formation in Listeria monocytogenes

Keeney, K., Trmcic, A., Zhu, Z., Delaquis, P., Wang, S.
Letters in applied microbiology 2018 v.67 no.6 pp. 530-536
Listeria monocytogenes, biofilm, equipment, food industry, food processing, genetic factors, genetic markers, genotype, plasmids, sequence analysis, serotypes
Listeria monocytogenes has a significant impact on the food industry by forming biofilms on food‐processing equipment. Tandem analysis of whole‐genome sequencing data with biofilm data from 166 environmental and food‐related L. monocytogenes isolates has revealed serotypic and genetic factors that strongly correlate with adherence and biofilm formation, such as lineage, plasmid harbourage, a three‐codon deletion in inlA and the presence of the stress survival islet 1 (SSI‐1). Strains from serotype 1/2b, the majority of which contained SSI‐1, formed the strongest biofilms, while serotype 4b strains, the majority of which did not contain SSI‐1, formed the weakest biofilms. When serotype 1/2a was separated by its SSI‐1 genotype, SSI‐1‐positive 1/2a strains demonstrated significantly higher capacity for biofilm formation after 3 days of growth at 30°C (P < 0·0001). Together, these findings indicate that SSI‐1 may contribute to serotype‐associated differences in the biofilm‐forming capacity in L. monocytogenes. SIGNIFICANCE AND IMPACT OF THE STUDY: Parallel analysis of whole‐genome sequences and serotype‐specific data was performed to identify genetic markers that correlate with increased adherence and biofilm formation in L. monocytogenes. The analyses revealed the hitherto unrecognized role of SSI‐1 in biofilm formation, contributing to deeper understanding of genetic factors that influence behaviour of the species in the food processing environment..