Multilocus sequence typing and rtxA toxin gene sequencing analysis of Kingella kingae isolates demonstrates genetic diversity and international clones.
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.


CONCLUSIONS
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.
Univ Paris Diderot, Sorbonne Paris Cité, EA 3105, Paris, France.
Romain
R
Basmaci
Pablo
P
Yagupsky
Brice
B
Ilharreborde
Kathleen
K
Guyot
Nurith
N
Porat
Marilyn
M
Chomton
Jean-Michel
JM
Thiberge
Keyvan
K
Mazda
Edouard
E
Bingen
Stéphane
S
Bonacorsi
Philippe
P
Bidet
D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics*; D001483:Base Sequence; D002999:Clone Cells / Q000378:metabolism; D020043:Genes, Essential / Q000235:genetics; D014644:Genetic Variation; D006801:Humans; D038622:Internationality; D017882:Kingella kingae / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010802:Phylogeny; D011110:Polymorphism, Genetic; D051381:Rats
D001427:Bacterial Toxins