Listeria monocytogenes exists in at least three evolutionary lines: evidence from flagellin, invasive associated protein and listeriolysin O genes

Abstract

Regions of the genes encoding flagellin (flaA), the invasive associated protein (iap), listeriolysin 0 (My) and 235 rRNA were sequenced for a range of Listeris monocytogenes isolates of different origin and serotypes. Several nucleotide sequence variations were found in the flaA, iap and hly genes. No differences were found for the rRNA genes, but our approach does not exclude the existence of differences between single copies of these genes. Based on the sequence differences, the L. monocytogenes strains can be divided into three distinct sequence types. Further, the presence of only a small number of sequence differences within each group indicates a strong degree of conservation within the groups. There was a complete correspondence among the groups of strains formed according to the analysis of the flaA, iap and hly genes, and the grouping correlates with serotype, pulsed field gel electrophoretic and multiloeus enzyme electrophoretic data. Analysis of the region encoding the threonine-asparagine repeat units in the iap gene revealed some striking features. Sequence type 1 strains were found to have 16-17 repeats, sequence type 2 strains had 16-20 repeats whereas the two sequence type 3 strains analysed had only 11 repeats. Furthermore, within a 19 bp segment there was a 37% difference between the sequences of type 1 and 2 strains and that segment was absent in type 3 strains. Within the threonine-asparagine repeat region the nucleotide differences gave rise to four amino acid changes; however, all were changes among the three amino acids present in the repeat structure indicating a strong selective pressure on the composition of this region.

Isolation of Listeria monocytogenes from the Skin of Slaughtered Beef Cattle

“…Although there was also a difference in the numbers of repeated sequences between 1E1 and 2E1, which were serotype 1/2b strains isolated in August and November, respectively, there were only two nucleotide substitutions between these strains. Taken together, comparison of the sequences among the same serotype isolates showed that the differences were mostly limited to the numbers of repeated sequences; this has previously been reported in detail as the polymorphic region of iap [10]. The obtained genetic similarity likely persistent contamination of L. monocytogenes around the area investigated in this study.…”

Characterization of virulent and avirulent Listeria monocytogenes strains by PCR amplification of putative transcriptional regulator and internalin genes

“…PCR detection of known L. monocytogenes virulence genes, such as inlA, inlB, actA, hlyA, plcA and plcB, has not proven suitable for differentiation of virulent and avirulent isolates (Nishibori et al, 1995), as these genes are consistently found in L. monocytogenes (Jaradat et al, 2002). Genetic lineage analysis has some predictive value for L. monocytogenes pathogenicity; however, the correlation between genetic lineages and pathogenicity is not consistent for all strains (Piffaretti et al, 1989;Rasmussen et al, 1995;Wiedmann et al, 1997). …”

Genetic and phenotypic characterization of Listeria monocytogenes lineage III

“…Two phylogenetic lineages were identified initially by multilocus enzyme electrophoresis (Piffaretti et al, 1989), and the existence of these lineages was subsequently confirmed by partial DNA sequencing of a virulence gene (Rasmussen et al, 1991), PFGE (Brosch et al, 1994) and ribotyping (Graves et al, 1994). Rasmussen et al (1995) provided the first evidence of a third L. monocytogenes phylogenetic lineage, lineage III, based on analyses of partial DNA sequences for flaA, iap and hly. Ribotyping and PCR-RFLP analyses of L. monocytogenes virulence genes, as well as comparative genomics and DNA sequencing studies, further confirmed the existence of at least three phylogenetic lineages in L. monocytogenes (Doumith et al, 2004;Ward et al, 2004;Wiedmann et al, 1997).…”