title: Temporal analysis of pathogenic events in virulent and avirulent Brucella melitensis infections.
abstract: Despite progress in mouse models of brucellosis, much remains unknown regarding Brucella dissemination and tissue localization. Here, we report the dynamics of Brucella infection in individual mice using bioluminescent Brucella melitensis. Bioluminescent imaging of infected interferon regulatory factor-1 knockout (IRF-1(-/-)) mice identified acute infection in many tissues. Brucella was found to replicate in the salivary glands of IRF-1(-/-) and wild-type C57BL/6 mice suggesting a previously unknown tissue preference. Establishing a niche in this region may have relevance in humans where infection can result from ingestion of few bacteria. Sublethal infection of IRF-1(-/-) mice resulted in chronic Brucella localization in tail joints, an infection parallel to osteoarticular brucellosis in humans. Importantly, bioluminescent imaging rapidly identified attenuated EZ::TN/lux mutants in infected mice and revealed differences in dissemination, thereby defining the contribution of Brucella genes to virulence and tissue localization. Surprisingly, a virB mutant, though defective in persistence, disseminated similarly to virulent Brucella, suggesting bacterial spread is independent of VirB proteins that are important for intracellular survival. Together, our results reveal kinetics of acute and chronic Brucella infection in individual mice that parallels human infection as well as readily identified attenuated bacteria. Our approach facilitates identifying virulence determinants that may control tissue specific replication and may help develop therapeutics to overcome Brucella-induced chronic debilitating conditions.
authors.affiliation: Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, 53706, USA.
authors.forename: Gireesh
authors.initials: G
authors.lastname: Rajashekara
authors.forename: David A
authors.initials: DA
authors.lastname: Glover
authors.forename: Michael
authors.initials: M
authors.lastname: Krepps
authors.forename: Gary A
authors.initials: GA
authors.lastname: Splitter
mesh_terms: D000818:Animals; D017347:Brucella melitensis / Q000472:pathogenicity*; D002006:Brucellosis / Q000382:microbiology* / Q000473:pathology*; D015169:Colony Count, Microbial; D004195:Disease Models, Animal; D005798:Genes, Bacterial; D050856:Interferon Regulatory Factor-1 / Q000235:genetics; D007596:Joints / Q000382:microbiology; D008164:Luminescent Proteins / Q000032:analysis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D012469:Salivary Glands / Q000382:microbiology; D013194:Staining and Labeling; D013997:Time Factors; D014774:Virulence / Q000235:genetics
chemical_list: D050856:Interferon Regulatory Factor-1; C494258:Irf1 protein, mouse; D008164:Luminescent Proteins