Ribotypes and virulence gene polymorphisms suggest three distinct Listeria monocytogenes lineages with differences in pathogenic potential

Abstract

A total of 133 Listeria monocytogenes isolates were characterized by ribotyping and allelic analysis of the virulence genes hly, actA, and inlA to uncover linkages between independent phylogenetic and specific virulence markers. PCR-restriction fragment length polymorphisms revealed 8 hly, 11 inlA, and 2 actA alleles. The combination of these virulence gene alleles and ribotype patterns separated L. monocytogenes into three distinct lineages. While distinct hly and inlA alleles were generally found to cluster into these three lineages, actA alleles segregated independently. These three phylogenetic lineages were confirmed when 22 partial actA DNA sequences were analyzed. The clinical history of the L. monocytogenes strains showed evidence for differences in pathogenic potential among the three lineages. Lineage I contains all strains isolated during epidemic outbreaks of listeriosis, while no human isolates were found in lineage III. Animal isolates were found in all three lineages. We found evidence that isolates from lineages I and III have a higher plaquing efficiency than lineage II strains in a cell culture assay. Strains from lineage III also seem to form larger plaques than strains from lineage II. A distinctive ribotype fragment and unique 16S rRNA gene sequences furthermore suggest that lineage III might represent a L. monocytogenes subspecies. None of the 20 human isolates available but 11% of our animal isolates were grouped in this lineage, indicating that strains in this lineage might have reduced virulence for humans.

Allelic exchange and site-directed mutagenesis probe the contribution of ActA amino-acid variability to phosphorylation and virulence-associated phenotypes amongListeria monocytogenesstrains

“…1). While previous studies have shown that isolates with three and four PRR are predominant in L. monocytogenes lineages I and II, respectively (Wiedmann et al, 1997), there were no significant associations between genetic lineage and number of PRRs among the isolates included in this study, supporting that this isolate set allows for comparisons of plaque size among isolates with three vs. four PRRs without lineage as a confounding factor. We thus conclude that the number of ActA PRRs is not associated with differences in plaque size among natural isolates, if isolates with three and four PRRs are equally represented within each lineage.…”

Use of Molecular Epidemiology in Veterinary Practice

“…Restriction methods can be combined with PCR methods. PCR can be the first step, followed by restriction of the amplified product, as in hemolysin typing of Listeria monocytogenes [35] or PCR-RFLP of Cryptosporidium parvum [36]. Alternatively, restriction can be followed by PCR, as in amplified fragment length polymorphism typing.…”

“…Staphylococcus aureus in veterinary teaching hospitals [120] Identification of genetic determinants of disease and disease transmission Lineage-specific pathogenicity of Listeria monocytogenes in humans and ruminants [35] Confirmation of epidemiologically suspected transmission Transmission of Staphylococcus aureus mastitis by flies [121] Detection of epidemiologically unsuspected outbreaks…”

Interactions between the environmental pathogen Listeria monocytogenes and a free‐living protozoan (Acanthamoeba castellanii)

“…As a species, L. monocytogenes is comprised of 13 serovars and at least two distinct genetic lineages (Piffaretti et al, 1989;Bibb et al, 1990;Ericsson et al, 2000;Call et al, 2003;Zhou et al, 2005). Serovars from one lineage (Division I; serovars 1/2b and 4b) have a greater predilection for causing disease in humans compared with serovars from the other lineage (Division II; serovars 1/2a and 1/2c) (Wiedmann et al, 1997).…”