title: Listeria monocytogenes strains encoding premature stop codons in inlA invade mice and guinea pig fetuses in orally dosed dams.
abstract: Listeria monocytogenes is an important food-borne bacterial pathogen and listeriosis can result in abortions in pregnant women. The bacterium can colonize food-processing environments, where specific molecular subtypes can persist for years. The purpose of this study was to determine the virulence potential of a group of food-processing persistent L. monocytogenes strains encoding a premature stop codon in inlA (encoding internalin A) by using two orally dosed models, pregnant mice and pregnant guinea pigs. A food-processing persistent strain of L. monocytogenes invaded placentas (n = 58; 10 % positive) and fetuses (3 % positive) of pregnant mice (n = 9 animals per strain), similar to a genetically manipulated murinized strain, EGD-e InlA(m*) (n = 61; 3 and 2 %, respectively). In pregnant guinea pigs (n = 9 animals per bacterial strain), a maternofetal strain (from a human fetal clinical fatal case) was isolated from 34 % of placenta samples (n = 50), whereas both food-processing persistent strains were found in 5 % of placenta samples (n = 36 or 37). One of the food-processing persistent strains, N53-1, was found in up to 8 % of guinea pig fetal liver and brain samples, whereas the maternofetal control was found in 6 % of fetal tissue samples. As the food-processing persistent strains carry a premature stop codon in inlA but are invasive in orally dosed pregnant mice and guinea pigs, we hypothesize that listerial crossing of the placental barrier can occur by a mechanism that is independent of an interaction between E-cadherin and InlA.
authors.affiliation: National Food Institute, Technical University of Denmark, Søltofts Plads, Bldg 221, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Anne
authors.initials: A
authors.lastname: Holch
authors.affiliation: Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark.
authors.forename: Hanne
authors.initials: H
authors.lastname: Ingmer
authors.affiliation: National Food Institute, Technical University of Denmark, Mørkhøj Bygade 19, DK-2860 Søborg, Denmark.
authors.forename: Tine Rask
authors.initials: TR
authors.lastname: Licht
authors.affiliation: Department of Systems Biology, Technical University of Denmark, Søltofts Plads, Bldg 221, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Lone
authors.initials: L
authors.lastname: Gram
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D001921:Brain / Q000382:microbiology; D018389:Codon, Nonsense / Q000235:genetics*; D005260:Female; D005333:Fetus / Q000382:microbiology*; D005516:Food Microbiology; D005525:Food-Processing Industry; D006168:Guinea Pigs; D008089:Listeria monocytogenes / Q000235:genetics*; D008088:Listeriosis / Q000235:genetics / Q000382:microbiology; D008099:Liver / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D011247:Pregnancy; D014774:Virulence / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D018389:Codon, Nonsense; C069761:internalin protein, Bacteria