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Updated: Mar 14, 2026
In vitro Biofilm Formation in an 8-well Chamber Slide
Published on: January 20, 2011
In vitro characterization of biofilms formed by Kingella kingae
J B Kaplan1, V Sampathkumar2, M Bendaoud2
1Department of Biology, American University, Washington, DC, USA.
Insights
Nearly half of Kingella kingae clinical isolates form biofilms, crucial for colonization and infection. Biofilm formation depends on pili and extracellular DNA, impacting bacterial pathogenesis and gene transfer.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Kingella kingae is a Gram-negative bacterium found in the oropharynx of young children.
- It can cause serious skeletal infections like septic arthritis and osteomyelitis, as well as infective endocarditis.
- Biofilm formation is linked to bacterial colonization and infection but had not been studied in K. kingae.
Purpose of the Study:
- To investigate the prevalence and characteristics of biofilm formation in clinical isolates of Kingella kingae.
- To identify factors contributing to biofilm development in K. kingae.
Main Methods:
- A crystal violet binding assay was used to measure biofilm formation in 79 K. kingae clinical isolates.
- The role of pili and extracellular components was assessed using a pilus gene cluster mutant and treatment with proteinase K and DNase I.
- Extracellular matrix composition was analyzed.
Main Results:
- 47% (37/79) of K. kingae isolates formed biofilms, characterized by corroding colonies on agar.
- Biofilm formation was inhibited by proteinase K and DNase I; DNase I also detached pre-formed biofilms.
- A pilus mutant (pilA1pilA2fimB) failed to form biofilms, autoaggregate, or produce corroding colonies.
- Biofilm-forming strains showed higher pilA1 expression.
- Extracellular biofilm components were rich in protein and DNA.
Conclusions:
- Biofilm formation is common in K. kingae clinical isolates.
- Biofilm development is dependent on proteinaceous pili and extracellular DNA.
- These findings suggest biofilm formation plays a role in K. kingae colonization, transmission, and pathogenesis.
- Extracellular DNA may also facilitate horizontal gene transfer in the oral microbiome.
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-2 of protein, 0.68 μg cm-2 of DNA, and 0.4 μg cm-2 of 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.
