title: Phenotypic and genomic analysis of hypervirulent human-associated Bordetella bronchiseptica.
abstract: BACKGROUND
  B. bronchiseptica infections are usually associated with wild or domesticated animals, but infrequently with humans. A recent phylogenetic analysis distinguished two distinct B. bronchiseptica subpopulations, designated complexes I and IV. Complex IV isolates appear to have a bias for infecting humans; however, little is known regarding their epidemiology, virulence properties, or comparative genomics.
  
  
  RESULTS
  Here we report a characterization of the virulence of human-associated complex IV B. bronchiseptica strains. In in vitro cytotoxicity assays, complex IV strains showed increased cytotoxicity in comparison to a panel of complex I strains. Some complex IV isolates were remarkably cytotoxic, resulting in LDH release levels in A549 cells that were 10- to 20-fold greater than complex I strains. In vivo, a subset of complex IV strains was found to be hypervirulent, with an increased ability to cause lethal pulmonary infections in mice. Hypercytotoxicity in vitro and hypervirulence in vivo were both dependent on the activity of the bsc T3SS and the BteA effector. To clarify differences between lineages, representative complex IV isolates were sequenced and their genomes were compared to complex I isolates. Although our analysis showed there were no genomic sequences that can be considered unique to complex IV strains, there were several loci that were predominantly found in complex IV isolates.
  
  
  CONCLUSIONS
  Our observations reveal a T3SS-dependent hypervirulence phenotype in human-associated complex IV isolates, highlighting the need for further studies on the epidemiology and evolutionary dynamics of this B. bronchiseptica lineage.
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California, BSRB 254, 615 Charles E, Young Drive East, Los Angeles, CA 90095-1747, USA.
authors.forename: Umesh
authors.initials: U
authors.lastname: Ahuja
authors.forename: Minghsun
authors.initials: M
authors.lastname: Liu
authors.forename: Shuta
authors.initials: S
authors.lastname: Tomida
authors.forename: Jihye
authors.initials: J
authors.lastname: Park
authors.forename: Puneet
authors.initials: P
authors.lastname: Souda
authors.forename: Julian
authors.initials: J
authors.lastname: Whitelegge
authors.forename: Huiying
authors.initials: H
authors.lastname: Li
authors.forename: Eric T
authors.initials: ET
authors.lastname: Harvill
authors.forename: Julian
authors.initials: J
authors.lastname: Parkhill
authors.forename: Jeff F
authors.initials: JF
authors.lastname: Miller
mesh_terms: D000818:Animals; D058947:Bacterial Secretion Systems / Q000235:genetics; D001885:Bordetella Infections / Q000453:epidemiology* / Q000382:microbiology*; D016950:Bordetella bronchiseptica / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D002460:Cell Line; D002470:Cell Survival; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000382:microbiology / Q000502:physiology; D005260:Female; D016680:Genome, Bacterial; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018410:Pneumonia, Bacterial / Q000382:microbiology / Q000401:mortality / Q000473:pathology; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D026801:Synteny; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D058947:Bacterial Secretion Systems; D037521:Virulence Factors