Molecular Tests That Target the RTX Locus Do Not Distinguish between Kingella kingae and the Recently Described Kingella negevensis Species

Abstract

is an important invasive pathogen in early childhood. The organism elaborates an RTX toxin presumably restricted to this species. Consequently, real-time quantitative PCR (qPCR) assays targeting the RTX locus have been developed in recent years and are gaining increasing use for the molecular diagnosis of infections. However, the present study shows that, a species newly identified in young children, harbors an identical RTX locus, raising the question of whether can be misidentified as by clinical microbiology laboratories. comparison of sp. RTX and genes and studies provided evidence that targeting the and genes could not differentiate between strains of and, whereas targeting the gene could. This prompted the design of a highly specific and sensitive qPCR assay targeting (). Ninety-nine culture-negative osteoarticular specimens from 99 children younger than 4 years of age were tested with a conventional 16S rRNA gene-based broad-range PCR assay and -specific, -specific (), and qPCR assays. Forty-two specimens were positive, including 41 that were also positive and 1 (the remaining one) that was positive. Thus, this study discloses an invasive infection caused by in humans and demonstrates that targeting the RTX locus cannot be used for the formal diagnosis of infections. These findings stress the need for further studies on the epidemiology of asymptomatic carriage and invasive infections caused by in humans.

Prevalence of Kingella kingae oropharyngeal carriage and predominance of type a and type b polysaccharide capsules among French young children

“…To reliably define a K. kingae carriage, we first identified the positive rtxA samples, and then we needed a negative groEL PCR (highly specific of Kingella negevensis) [5], to discriminate K. kingae (rtxAþ/groELe) from K. negevensis (rtxAþ/groELþ). No rtxAþ/ groEL þ samples were found, which excluded the possibility of a mixed colonization.…”

Real-Time PCR Assay for Detection of Kingella kingae in Children

“…39 Recent reports also suggest that K. negevensis sp. nov., like K. kingae, can colonize the oropharynx of children; 24,38 given this and that it has the same RTX gene locus, 39,40 it is possible that K. negevensis sp. nov. may be a cause of OAI in children, but further studies on this subject are required.…”

“…nov., 24,38 as expected based on the performance of other assays targeting the RTX gene locus. 39 rtxB has been used as a PCR target by other investigators, 14 as has rtxA. 14,21 Others have used the housekeeping gene cpn60.…”

Detection of Respiratory Colonization by Kingella kingae and the Novel Kingella negevensis Species in Children: Uses and Methodology

“…nov. (2). The organism has also been detected in France, Switzerland, and the United States (25,26), indicating a wide geographical distribution, although it has not been isolated yet from patients with invasive infection. Kingella negevensis exhibits genomic heterogeneity, and a few clones, defined by distinct PFGE and sequencing profiles of the 16S rRNA and groEL genes, predominated in a healthy carrier population (2).…”