title: RTX toxin plays a key role in Kingella kingae virulence in an infant rat model.
abstract: Kingella kingae is a human oral bacterium that can cause diseases of the skeletal system in children and infective endocarditis in children and adults. K. kingae produces a toxin of the RTX group, RtxA. To investigate the role of RtxA in disease pathogenesis in vivo, K. kingae strain PYKK081 and its isogenic RtxA-deficient strain KKNB100 were tested for their virulence and pathological consequences upon intraperitoneal injections in 7-day-postnatal (PN 7) rats. At the doses above 8.0 × 10(6) cells/animal, PYKK081 was able to cause a fatal illness, resulting in rapid weight loss, bacteremia, and abdominal necrotic lesion formation. Significant histopathology was observed in thymus, spleen, and bone marrow. Strain KKNB100 was less toxic to animals. Neither weight loss, bacteremia, nor histopathological changes were evident. Animals injected with KKNB100 exhibited a significantly elevated circulating white blood cell (WBC) count, whereas animals injected with PYKK081 had a WBC count that resembled that of the uninfected control. This observation parallels the subtleties associated with clinical presentation of K. kingae disease in humans and suggests that the toxin contributes to WBC depletion. Thus, our results demonstrate that RtxA is a key K. kingae virulence factor. Furthermore, our findings suggest that the PN 7 rat can serve as a useful model for understanding disease caused by K. kingae and for elucidating diagnostic parameters in human patients.
authors.affiliation: Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, New Jersey, USA.
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Chang
authors.forename: Yoav A
authors.initials: YA
authors.lastname: Nudell
authors.forename: Jenny
authors.initials: J
authors.lastname: Lau
authors.forename: Eleonora
authors.initials: E
authors.lastname: Zakharian
authors.forename: Nataliya V
authors.initials: NV
authors.lastname: Balashova
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D017882:Kingella kingae / Q000472:pathogenicity*; D007958:Leukocyte Count; D016870:Neisseriaceae Infections / Q000382:microbiology* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014774:Virulence / Q000502:physiology*
chemical_list: D001427:Bacterial Toxins