title: Reproducible and quantitative model of infection of Dermacentor variabilis with the live vaccine strain of Francisella tularensis.
abstract: Pathogen life cycles in mammalian hosts have been studied extensively, but studies with arthropod vectors represent considerable challenges. In part this is due to the difficulty of delivering a reproducible dose of bacteria to follow arthropod-associated replication. We have established reproducible techniques to introduce known numbers of Francisella tularensis strain LVS from mice into Dermacentor variabilis nymphs. Using this model infection system, we performed dose-response infection experiments and followed bacterial replication through the molt to adults and at later time points. During development to adults, bacteria replicate to high numbers and can be found associated with the gut tissues, salivary glands, and hemolymph of adult ticks. Further, we can transmit a mutant of LVS (LVS ΔpurMCD) that cannot replicate in macrophages in vitro or in mice to nymphs. Our data show that the LVS ΔpurMCD mutant cannot be transstadially transmitted from nymphs to adult ticks. We then show that a plasmid-complemented strain of this mutant is recoverable in adult ticks and necessary for bacterial replication during the molt. In a mixed-infection assay (ΔpurMCD mutant versus ΔpurMCD complement), 98% of the recovered bacteria retained the plasmid marker. These data suggest that the ΔpurMCD mutation cannot be rescued by the presence a complemented strain in a mixed infection. Importantly, our infection model provides a platform to test specific mutants for their replication in ticks, perform competition studies, and use other genetic techniques to identify F. tularensis genes that are expressed or required in this unique environment.
authors.affiliation: Department of Medicine, Division of Infectious Diseases, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Jenifer
authors.initials: J
authors.lastname: Coburn
authors.affiliation: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Tamara
authors.initials: T
authors.lastname: Maier
authors.affiliation: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Monika
authors.initials: M
authors.lastname: Casey
authors.affiliation: Department of Medicine, Division of Infectious Diseases, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Lavinia
authors.initials: L
authors.lastname: Padmore
authors.affiliation: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Sato
authors.affiliation: Department of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA Center for Infectious Disease Research, Medical College of Wisconsin, Milwaukee, Wisconsin, USA frankd@mcw.edu.
authors.forename: Dara W
authors.initials: DW
authors.lastname: Frank
mesh_terms: D000825:Animal Structures / Q000382:microbiology; D000818:Animals; D001428:Bacterial Vaccines; D003870:Dermacentor / Q000382:microbiology*; D004195:Disease Models, Animal; D018562:Disease Transmission, Infectious; D004199:Disease Vectors; D005604:Francisella tularensis / Q000254:growth & development*; D051379:Mice; D015203:Reproducibility of Results; D014406:Tularemia / Q000382:microbiology* / Q000635:transmission; D014613:Vaccines, Attenuated
chemical_list: D001428:Bacterial Vaccines; D014613:Vaccines, Attenuated