Abstract
Background Kingella kingae, a normal component of the upper respiratory flora, is being increasingly recognized as an important invasive pathogen in young children. Genetic diversity of this species has not been studied.MethodsWe analyzed 103 strains from different countries and clinical origins by a new multilocus sequence-typing (MLST) schema. Putative virulence gene rtxA, encoding an RTX toxin, was also sequenced, and experimental virulence of representative strains was assessed in a juvenile-rat model.ResultsThirty-six sequence-types (ST) and nine ST-complexes (STc) were detected. The main STc 6, 14 and 23 comprised 23, 17 and 20 strains respectively, and were internationally distributed. rtxA sequencing results were mostly congruent with MLST, and showed horizontal transfer events. Of interest, all members of the distantly related ST-6 (n = 22) and ST-5 (n = 4) harboured a 33 bp duplication or triplication in their rtxA sequence, suggesting that this genetic trait arose through selective advantage. The animal model revealed significant differences in virulence among strains of the species.ConclusionMLST analysis reveals international spread of ST-complexes and will help to decipher acquisition and evolution of virulence traits and diversity of pathogenicity among K. kingae strains, for which an experimental animal model is now available.
Highlights
Increasing use of improved culture methods and sensitive nucleic acid amplification assays in recent years has resulted in the recognition of Kingella kingae as a common etiology of skeletal system infections and bacteremia below the age of 3 years [1,2,3,4,5,6,7,8,9,10,11]
Genotyping of 240 strains derived from healthy carriers by pulsed-field gel electrophoresis (PFGE) demonstrated 40 distinct clones of which a few were undistinguishable from those detected among isolates from patients with invasive infections [20]
In the present study we studied the genetic diversity of 103 K. kingae isolates from different countries and different clinical sources by use of a new multi-locus sequence-typing (MLST) scheme
Summary
Increasing use of improved culture methods and sensitive nucleic acid amplification assays in recent years has resulted in the recognition of Kingella kingae as a common etiology of skeletal system infections and bacteremia below the age of 3 years [1,2,3,4,5,6,7,8,9,10,11]. Genotyping of 240 strains derived from healthy carriers by pulsed-field gel electrophoresis (PFGE) demonstrated 40 distinct clones of which a few were undistinguishable from those detected among isolates from patients with invasive infections [20]. These preliminary results indicate that K. kingae exhibits genetic heterogeneity, development of a highly reproducible genotyping method is necessary to decipher the genetic organization of the species and determine whether certain genotypes are associated with either carriage or disease. A normal component of the upper respiratory flora, is being increasingly recognized as an important invasive pathogen in young children Genetic diversity of this species has not been studied
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