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Infectious Diseases - Microbiology - Pediatrics and Child Health - Public Health and Epidemiology


Multilocus Sequence Typing and rtxA Toxin Gene Sequencing Analysis of Kingella kingae Isolates Demonstrates Genetic Diversity and International Clones
Published: Thursday, May 31, 2012
Author: Romain Basmaci et al.

by Romain Basmaci, Pablo Yagupsky, Brice Ilharreborde, Kathleen Guyot, Nurith Porat, Marilyn Chomton, Jean-Michel Thiberge, Keyvan Mazda, Edouard Bingen, St├ęphane Bonacorsi, Philippe Bidet

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.

Methods

We 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.

Results

Thirty-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.

Conclusion

MLST 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.

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