Molecular Tests That Target the RTX Locus Do Not Distinguish between Kingella kingae and the Recently Described Kingella negevensis Species
Molecular Tests That Target the RTX Locus Do Not Distinguish between Kingella kingae and the Recently Described Kingella negevensis Species
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DOI：
10.1128/jcm.00736-17
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发表时间：
2017-10-01
影响因子：
9.4
通讯作者：
Fournier, Pierre-Edouard
中科院分区：
文献类型：
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作者：
El Houmami, Nawal;Bzdrenga, Janek;Fournier, Pierre-Edouard
Kingella kingae是一种重要的儿童早期侵袭性病原体。这种有机体产生一种RTX毒素，推测仅限于该物种。因此，针对rtx基因座的实时定量聚合酶链式反应(QPCR)技术近年来得到发展，并越来越多地用于国王克雷伯氏菌感染的分子诊断。然而，本研究表明，在儿童中新发现的金格拉属物种具有相同的金格拉RTX基因座，这引发了临床微生物学实验室是否可以将金格拉金格氏菌误认为国王克雷伯氏菌的问题。金龟子属(Kingella sp.)Rtx和groEL基因以及体外研究提供的证据表明，靶向rtxA和rtxB基因不能区分国王克雷伯氏菌和革兰氏克雷伯氏菌，而靶向GroEL基因则可以。这促使人们设计了一种针对克雷伯氏菌GroEL(KngroEL)的高度特异和敏感的定量聚合酶链式反应方法。对99名4岁以下儿童的99份培养阴性的骨关节标本进行了常规的基于16SRRNA基因的广谱聚合酶链式反应(16SRRNA)、金革兰特异性rtxB、金黄色葡萄球菌特异性GroEL(KkgroEL)和KngroEL qPCR检测。RtxB阳性42例，其中kkgroEL阳性41例，kgroEL阳性1例。因此，本研究揭示了一种由革兰氏克雷伯氏菌在人类中引起的侵袭性感染，并证明靶向RTX基因座不能用于国王克雷伯菌感染的正式诊断。这些发现强调了进一步研究无症状携带者和由克雷伯氏菌引起的人类侵袭性感染的流行病学的必要性。
Kingella kingae 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 K. kingae infections. However, the present study shows that Kingella negevensis, a Kingella species newly identified in young children, harbors an identical Kingella RTX locus, raising the question of whether K. negevensis can be misidentified as K. kingae by clinical microbiology laboratories. In silico comparison of Kingella sp. RTX and groEL genes and in vitro studies provided evidence that targeting the rtxA and rtxB genes could not differentiate between strains of K. kingae and K. negevensis, whereas targeting the groEL gene could. This prompted the design of a highly specific and sensitive qPCR assay targeting K. negevensis groEL (kngroEL). 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 Kingella-specific rtxB, K. kingae-specific groEL (kkgroEL), and kngroEL qPCR assays. Forty-two specimens were rtxB positive, including 41 that were also kkgroEL positive and 1 (the remaining one) that was kngroEL positive. Thus, this study discloses an invasive infection caused by K. negevensis in humans and demonstrates that targeting the RTX locus cannot be used for the formal diagnosis of K. kingae infections. These findings stress the need for further studies on the epidemiology of asymptomatic carriage and invasive infections caused by K. negevensis in humans.