Positive Correlation Between the Expression of inlA and inlB Genes of Listeria monocytogenes and Its Attachment Strength on Glass Surface

Abstract

Previous research involving internalin A (inlA) and internalin B (inlB) single- and double-knockout mutants of Listeria monocytogenes has suggested the involvement of two surface proteins, InlA and InlB, in the adherence of the cells to a glass surface. This phenomenon was further investigated with a larger number (n = 27) of L. monocytogenes wild-type strains that were isolated from catfish processing plants and catfish fillets, in addition to internal controls, one ATCC 7644 strain, and L. monocytogenes EGDe strain. Of the wild-type strains, three were shown to produce truncated forms of InlA protein. A blot succession method was used to measure the ease of detachment of sessile L. monocytogenes from a glass surface after attachment at 4 °C for 8 h. Real-time reverse transcriptase polymerase chain reaction was used to quantitate mRNA levels of inlA and inlB in L. monocytogenes strains after the cells were incubated at 4 °C for 8 h. An inverse relationship between the ease of cell removal from glass surface and the relative inlA and inlB mRNA levels with R2 value of 0.664 and 0.431, respectively, was observed. This suggests that the attachment strength of L. monocytogenes on glass surface is positively correlated with inlA and inlB expression. There were no differences (p > 0.05) in attachment strength among serotypes. These results suggest that L. monocytogenes InlA and InlB proteins play a role in adherence to a glass surface at low temperature, and the attachment ability is independent of serotype.