Related Experiment Video
Updated: Mar 13, 2026
Separating Bacteria by Capsule Amount Using a Discontinuous Density Gradient
Published on: January 7, 2019
Kingella kingae Expresses Four Structurally Distinct Polysaccharide Capsules That Differ in Their Correlation with
Kimberly F Starr1, Eric A Porsch2, Patrick C Seed1
1Department of Pediatrics and Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC.
Insights
Kingella kingae has at least four distinct capsule types (a, b, c, and d), determined by specific gene loci. Invasive strains predominantly express type a or b, suggesting capsule type influences disease potential.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Kingella kingae is a common cause of osteoarticular infections in children.
- Previous research identified the csaA gene involved in type a capsule synthesis.
Purpose of the Study:
- To investigate the genetic basis of capsule diversity in Kingella kingae.
- To determine the role of different gene loci in capsule synthesis and their association with invasive disease.
Main Methods:
- Analysis of invasive and carrier isolates using PCR and sequencing.
- Genetic manipulation by introducing gene loci into a K. kingae mutant strain.
- Characterization of polysaccharide capsule structures.
Main Results:
- Identified three novel gene clusters (csb, csc, csd) in addition to csaA, responsible for distinct capsule types (b, c, and d).
- Demonstrated that these four loci (csa, csb, csc, csd) are solely responsible for K. kingae capsule type determination.
- Found that invasive isolates predominantly express type a or b capsules, while carrier isolates are more likely to express type c or d.
Conclusions:
- There are at least four structurally distinct Kingella kingae capsule types.
- Capsule type is a significant factor in the pathogenesis of invasive Kingella kingae disease.
Abstract:
Kingella kingae is an encapsulated gram-negative organism that is a common cause of osteoarticular infections in young children. In earlier work, we identified a glycosyltransferase gene called csaA that is necessary for synthesis of the [3)-β-GalpNAc-(1→5)-β-Kdop-(2→] polysaccharide capsule (type a) in K. kingae strain 269-492. In the current study, we analyzed a large collection of invasive and carrier isolates from Israel and found that csaA was present in only 47% of the isolates. Further examination of this collection using primers based on the sequence that flanks csaA revealed three additional gene clusters (designated the csb, csc, and csd loci), all encoding predicted glycosyltransferases. The csb locus contains the csbA, csbB, and csbC genes and is associated with a capsule that is a polymer of [6)-α-GlcpNAc-(1→5)-β-(8-OAc)Kdop-(2→] (type b). The csc locus contains the cscA, cscB, and cscC genes and is associated with a capsule that is a polymer of [3)-β-Ribf-(1→2)-β-Ribf-(1→2)-β-Ribf-(1→4)-β-Kdop-(2→] (type c). The csd locus contains the csdA, csdB, and csdC genes and is associated with a capsule that is a polymer of [P-(O→3)[β-Galp-(1→4)]-β-GlcpNAc-(1→3)-α-GlcpNAc-1-] (type d). Introduction of the csa, csb, csc, and csd loci into strain KK01Δcsa, a strain 269-492 derivative that lacks the native csaA gene, was sufficient to produce the type a capsule, type b capsule, type c capsule, and type d capsule, respectively, indicating that these loci are solely responsible for determining capsule type in K. kingae. Further analysis demonstrated that 96% of the invasive isolates express either the type a or type b capsule and that a disproportionate percentage of carrier isolates express the type c or type d capsule. These results establish that there are at least four structurally distinct K. kingae capsule types and suggest that capsule type plays an important role in promoting K. kingae invasive disease.
