title: In vitro characterization of biofilms formed by Kingella kingae.
abstract: The Gram-negative bacterium Kingella kingae is part of the normal oropharyngeal mucosal flora of children <4 years old. K. kingae can enter the submucosa and cause infections of the skeletal system in children, including septic arthritis and osteomyelitis. The organism is also associated with infective endocarditis in children and adults. Although biofilm formation has been coupled with pharyngeal colonization, osteoarticular infections, and infective endocarditis, no studies have investigated biofilm formation in K. kingae. In this study we measured biofilm formation by 79 K. kingae clinical isolates using a 96-well microtiter plate crystal violet binding assay. We found that 37 of 79 strains (47%) formed biofilms. All strains that formed biofilms produced corroding colonies on agar. Biofilm formation was inhibited by proteinase K and DNase I. DNase I also caused the detachment of pre-formed K. kingae biofilm colonies. A mutant strain carrying a deletion of the pilus gene cluster pilA1pilA2fimB did not produce corroding colonies on agar, autoaggregate in broth, or form biofilms. Biofilm forming strains have higher levels of pilA1 expression. The extracellular components of biofilms contained 490 μg cm-2of protein, 0.68 μg cm-2of DNA, and 0.4 μg cm-2of total carbohydrates. We concluded that biofilm formation is common among K. kingae clinical isolates, and that biofilm formation is dependent on the production of proteinaceous pili and extracellular DNA. Biofilm development may have relevance to the colonization, transmission, and pathogenesis of this bacterium. Extracellular DNA production by K. kingae may facilitate horizontal gene transfer within the oral microbial community.
authors.affiliation: Department of Biology, American University, Washington, DC, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Kaplan
authors.affiliation: Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA.
authors.forename: V
authors.initials: V
authors.lastname: Sampathkumar
authors.affiliation: Department of Oral Biology, Rutgers School of Dental Medicine, Rutgers University, Newark, NJ, USA.
authors.forename: M
authors.initials: M
authors.lastname: Bendaoud
authors.affiliation: Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Giannakakis
authors.affiliation: Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: E T
authors.initials: ET
authors.lastname: Lally
authors.affiliation: Department of Pathology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: N V
authors.initials: NV
authors.lastname: Balashova
mesh_terms: D018441:Biofilms / Q000187:drug effects / Q000254:growth & development*; D002648:Child; D002675:Child, Preschool; D003850:Deoxyribonuclease I / Q000494:pharmacology; D019286:Endopeptidase K / Q000494:pharmacology; D036781:Fimbriae Proteins / Q000172:deficiency / Q000235:genetics; D010861:Fimbriae, Bacterial / Q000378:metabolism; D022761:Gene Transfer, Horizontal; D006801:Humans; D017882:Kingella kingae / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D016870:Neisseriaceae Infections / Q000382:microbiology / Q000635:transmission; D010019:Osteomyelitis / Q000382:microbiology
chemical_list: D036781:Fimbriae Proteins; D003850:Deoxyribonuclease I; D019286:Endopeptidase K
keywords: 
  Kingella kingae
  ; biofilms; oral microbiology