Selection of specific target genes of Kingella kingae and investigation of carrier rate in healthy people

ObjectiveTo analyze the specificity of target genes used in specific PCR detection of Kingella kingae and select suitable assay for the K. kingae carriage investigation in healthy population in China.

MethodsBy comparing the relationship of 16S rDNA, groEL and rtxA genes with other closely related gene sequences published in National Center for Biotechnology Information (NCBI) database, the conservation of three target genes in K. kingae was analyzed. The specificity, sensitivity and stability of the selected real-time PCR were verified. By using the established assay, 513 pharyngeal swabs were detected.

ResultsPhylogenetic tree based on rtxA gene showed high homology among different strains of K. kingae, and the similarity of rtxA gene with Moraxella bovis was 72%. rtxA gene was more conservative and specific than 16S rDNA and groEL genes, which is more suitable for the detection of K. kingae. The real-time quantitative PCR assay for K. kingae was proved to be rapid, specific, sensitive and reproducible, the detection sensitivity was 1copies/μl．For 513 pharynx swabs, 107 were detected positive (20.86%).

ConclusionrtxA gene is highly conserved in K. kingae and can be used as a target gene for nucleic acid detection. Real-time PCR based on rtxA showed that K. kingae had a high carriage rate in healthy population with certain age distribution characteritics in China.