Abstract
Kingella kingae is an encapsulated Gram-negative bacterium and an important etiology of osteoarticular infections in young children. A recent study examining a diverse collection of carrier and invasive K.kingae isolates from Israel revealed four distinct polysaccharide capsule types. In this study, to obtain a global view of K.kingae capsule type diversity, we examined an international collection of isolates using a multiplex PCR approach. The collection contained all four previously identified capsule types and no new capsule types. Over 95% of invasive isolates in the collection were type a or type b, similar to the findings in Israel. These results suggest that the type a and type b polysaccharide capsules may have enhanced pathogenic properties or may mark clonal groups of strains with specific virulence genes. In addition, they raise the possibility that a vaccine containing the type a and type b capsules might be an effective approach to preventing K.kingae disease. IMPORTANCEKingella kingae has emerged as a significant cause of septic arthritis, osteomyelitis, and bacteremia in young children. A recent study examining a diverse collection of K.kingae isolates from Israel revealed four different polysaccharide capsule types in this species, designated types a to d. To determine the global distribution of K.kingae capsule types, we assembled and capsule typed an international collection of K.kingae isolates. The findings reported here show that the type a and type b capsules represent >95% of the invasive isolates, similar to the Israeli isolate collection, suggesting that a polysaccharide-based vaccine targeting these two capsules could be an attractive approach to prevent K.kingae disease.
Highlights
The use of improved culture techniques and PCR-based diagnostics in recent years has revealed that the Gram-negative bacterium Kingella kingae is a significant etiology of osteoarticular infections in children 6 to 48 months of age in countries where these sensitive detection methods are routinely employed (1)
Recognizing that the use of species-specific nucleic acid amplification improves the detection of K. kingae by 500% compared to its detection by culture, the true incidence of K. kingae invasive disease in the Israeli population is likely comparable to the incidence of invasive Haemophilus influenzae type b disease before the introduction of H. influenzae type b conjugate vaccines (Hib conjugate vaccines) (i.e., Ͼ50 per 100,000) (10)
We found that four distinct polysaccharide capsule structures were present in this collection and that Ͼ95% of invasive disease isolates expressed the type a or type b capsule
Summary
The use of improved culture techniques and PCR-based diagnostics in recent years has revealed that the Gram-negative bacterium Kingella kingae is a significant etiology of osteoarticular infections in children 6 to 48 months of age in countries where these sensitive detection methods are routinely employed (1). KEYWORDS Kingella kingae, PCR, capsule typing, clinical isolates, polysaccharide capsule Recent studies have shown that isolates of K. kingae elaborate a polysaccharide capsule (11–13).
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