This analysis revealed three major branches (Figure 1) probably corresponding to the lineages I, II and IV described by Ward et al. by a SNP analysis [12]. In their study lineages I and III isolates formed, indeed, a sister group to lineage II strains, while the lineage IV represented a divergent sister clade. However, the small number of lineage IV strains did not allow us to conclude in this distribution. Nonetheless, as observed by Ward et al., lineage I included strains of serotype 1/2b, 4b, 4d, 4e, 3b and 7, whereas lineage II included strains of serotype 1/2a, 1/2c and 3a. Lineage III and IV included strains Daporinad nmr of serotype 4a, 4b and 4c. PFGE typing of the 92 isolates resulted in 69 different
patterns, most of them click here grouped into 16 clusters with a similarity percentage above 85%. All strains gave interpretable PFGE patterns after restriction by AscI enzyme, whereas three virulent strains of lineage III/IV (serotype 4a and 4c) gave no profiles after ApaI restriction, possibly due to the methylation of restriction sites [13, 14]. Figure 1 Dendrogram constructed for PFGE analysis using the UPGMA method with BioNumerics v.4.6 software showing the genetic relationships between 92 L. monocytogenes strains. The low-virulence strains are in red. Green lines indicate the division into clusters of strains having 85% similarity. Phenotypic groups were based on results
of cellular entry, plaque formation, and the two phospholipase C activities. Genotypic Groups were defined as follows: ACP-196 cost Group-Ib included the strains with PrfAK220T. Group-Ia included the strains with PrfAΔ174-237. Group-IIIa had the same mutations in the plcA, inlA and inlB genes. Group-Ic showed the K130Q mutation. No clear correlation could be made between the PFGE clusters and the virulence levels of the strains and even though seven clusters included only virulent strains, 5-FU purchase the low-virulence
strains were distributed in 9 clusters out of 16 (indicated by green lines in Figure 1), often mixed with virulent strains. Within the same lineage, the low-virulence strains were clustered according to their serotype. This observation is supported by the fact that strain NP26 belongs to the phenotypic Group-I which was grouped in lineage I with serotype 4b strains, whereas all the other strains of the phenotypic Group-I were grouped in lineage II with serotype 1/2a strains. In the lineage II, the low-virulence strains were grouped according to their genotyping Groups, but were sometimes clustered with virulent strains. Only strains of the genotypic Group-Ia formed one specific cluster. All strains of the genotypic Group-IIIa were grouped together, but on the same branch as strain A23 (similarity percentage >80%). This clustering can be explained by the demonstration that the A23 strain had the same genotypic mutations as the Group-IIIa strains, but exhibited some virulence in our in vivo and in vitro virulence tests [15].