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 … Show more
“…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.…”
To test the hypothesis that actA allelic variation contributes to virulence differences among Listeria monocytogenes strains, cell-to-cell spread and intracellular ActA phosphorylation patterns were characterized for 14 wild-type isolates and selected isogenic mutants. Our data show that (i) while actA allelic variation is not responsible for enhanced cell-to-cell spread observed in epidemic clone I strains, actA allelic variation may contribute to reduced plaque size observed in some isolates, (ii) actA sequence alone determines phosphorylation-dependent ActA banding patterns, and (iii) sequence variation at the positively selected ActA residue 498 does not contribute to ActA phosphorylation patterns or to differences in cell-to-cell spread.
“…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.…”
To test the hypothesis that actA allelic variation contributes to virulence differences among Listeria monocytogenes strains, cell-to-cell spread and intracellular ActA phosphorylation patterns were characterized for 14 wild-type isolates and selected isogenic mutants. Our data show that (i) while actA allelic variation is not responsible for enhanced cell-to-cell spread observed in epidemic clone I strains, actA allelic variation may contribute to reduced plaque size observed in some isolates, (ii) actA sequence alone determines phosphorylation-dependent ActA banding patterns, and (iii) sequence variation at the positively selected ActA residue 498 does not contribute to ActA phosphorylation patterns or to differences in cell-to-cell spread.
“…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.…”
Section: Molecular Methodsmentioning
confidence: 99%
“…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…”
Molecular epidemiology is a relatively new branch of epidemiology that uses molecular biology methods to study health and disease in populations. This article gives an introduction to molecular epidemiologic terminology and methodology and its usefulness in large animal medicine and veterinary public health. Applications in source tracing and vaccine studies and insights into transmission dynamics, host specificity, and niche adaptation of infectious organisms are presented. Examples are drawn from a variety of diseases, organisms, and host species and range from the global level to the individual-animal level.
“…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).…”
Listeria monocytogenes can cause severe disease in animal hosts, but it has no recognized animal host reservoir. We tested the hypothesis that L. monocytogenes retains virulence traits to survive predation by amoebae and that listeriolysin O plays a crucial role in this process. Co-culturing of L. monocytogenes and Acanthamoeba castellanii demonstrated that L. monocytogenes does not actively kill amoebae, but in the presence of amoebae, high bacterial population densities can be maintained over a period of at least 96 h. A gentamicin protection assay demonstrated that there is no significant difference in the ability to survive predation between serovars (4b versus 1/2a and 1/2c; P = 0.08) and between five species of Listeria (P = 0.14). Three of these species do not harbour the hly gene responsible for listeriolysin O production. A hly knockout strain had poorer survival compared with the parental strain (P = 0.04 at 24 h; P = 0.04 at 48 h; P = 0.02 at 72 h) and electron microscopy was consistent with a wild-type strain being able to escape the phagosome whereas the hly knockout strain did not appear to have this ability. Thus, while there is weak evidence that listeriolysin O can contribute to improved survival after ingestion by amoebae, listeriolysin O does not appear to provide a significant selective advantage under the conditions of this study.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.