High rates of homologous recombination in the mite endosymbiont and opportunistic human pathogen Orientia tsutsugamushi.
High rates of homologous recombination in the mite endosymbiont and opportunistic human pathogen Orientia tsutsugamushi.
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DOI：
10.1371/journal.pntd.0000752
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发表时间：
2010-07-20
影响因子：
3.8
通讯作者：
Day NP
中科院分区：
文献类型：
--
作者：
Sonthayanon P;Peacock SJ;Chierakul W;Wuthiekanun V;Blacksell SD;Holden MT;Bentley SD;Feil EJ;Day NP
恙虫病东方体（Orientia tsugamushi）是恙螨体内的一种胞内α-变形杆菌，是东亚地区恙虫病的病原体。该物种的基因组序列揭示了前所未有数量的重复序列，最值得注意的是编码IV型分泌系统（T4 SS）的接合特性的基因。尽管这一观察结果与频繁的基因组内重组一致，但该物种的同源重组（基因转换）程度尚不清楚。为了解决这个问题，并提供一个协议的流行病学监测这一重要的病原体，我们已经开发了一个多位点序列分型（MLST）计划的基础上7管家基因（gpsA，mdh，nrdB，nuoF，ppdK，sucD，sucB）。我们将此方案应用于两个已发表的基因组，并从84名泰国恙虫病患者的血液中提取的DNA，从20个培养的泰国患者分离株，1个澳大利亚患者样本，并从3个培养的典型菌株。这些数据表明，O.恙虫病种群具有高度多样性[Simpson指数（95%CI）= 0.95（0.92-0.98）]和高度重组性。 考虑到该物种的细胞内生活方式，这些结果令人惊讶，但与Wolbachia获得的结果大致一致，Wolbachia是节肢动物的α-变形菌生殖寄生虫。我们还将MLST数据与ompA序列数据进行了比较，并注意到MLST的一致性水平较低，区分度高得多。最后，在这项研究中，25%的患者同时感染了多种序列类型，这表明多重感染是由多个螨叮咬或多个菌株共存于单个螨中引起的。恙虫病是由专性细胞内细菌恙虫病东方体引起的立克次体传染病，是亚太地区的地方病。该细菌通过恙螨（“恙螨”;纤恙螨属）幼虫阶段的叮咬传播，它们通常以小型啮齿动物为食临床特征包括发烧、头痛、肌痛、淋巴结病和咬伤部位的焦痂。尽管这种病原体的重要性，很少有人知道的人口多样性或同源重组的作用，在驱动该物种的微进化。在这里，我们描述了一个多位点序列分型（MLST）计划，可以直接应用于血液样本的发展和应用，并适用于108 O。恙虫病分离株。我们发现这种生物表现出很高的同源重组率，这是一个令人惊讶的发现，考虑到这种物种的细胞内生活方式。我们还发现，在我们的研究中，25%的患者同时感染了多种序列类型，这表明多重感染是由多个螨叮咬或多个菌株共存于单个螨中引起的。
Orientia tsutsugamushi is an intracellular α-proteobacterium which resides in trombiculid mites, and is the causative agent of scrub typhus in East Asia. The genome sequence of this species has revealed an unprecedented number of repeat sequences, most notably of the genes encoding the conjugative properties of a type IV secretion system (T4SS). Although this observation is consistent with frequent intragenomic recombination, the extent of homologous recombination (gene conversion) in this species is unknown. To address this question, and to provide a protocol for the epidemiological surveillance of this important pathogen, we have developed a multilocus sequence typing (MLST) scheme based on 7 housekeeping genes (gpsA, mdh, nrdB, nuoF, ppdK, sucD, sucB). We applied this scheme to the two published genomes, and to DNA extracted from blood taken from 84 Thai scrub typhus patients, from 20 cultured Thai patient isolates, 1 Australian patient sample, and from 3 cultured type strains. These data demonstrated that the O. tsutsugamushi population was both highly diverse [Simpson's index (95% CI) = 0.95 (0.92–0.98)], and highly recombinogenic. These results are surprising given the intracellular life-style of this species, but are broadly consistent with results obtained for Wolbachia, which is an α-proteobacterial reproductive parasite of arthropods. We also compared the MLST data with ompA sequence data and noted low levels of consistency and much higher discrimination by MLST. Finally, twenty-five percent of patients in this study were simultaneously infected with multiple sequence types, suggesting multiple infection caused by either multiple mite bites, or multiple strains co-existing within individual mites. Scrub typhus, the rickettsial infectious disease caused by the obligate intracellular bacterium Orientia tsutsugamushi, is endemic across the Asia Pacific region. The bacterium is transmitted by the bite of larval stages of trombiculid mites (“chiggers”; Leptotrombidium spp.), which more typically feed on small rodents. Clinical features include fever, headache, myalgia, lymphadenopathy and an eschar at the site of the bite. Despite the importance of this pathogen, little is known of the population diversity or the role of homologous recombination in driving the microevolution of this species. Here, we describe the development and application of a multilocus sequence typing (MLST) scheme that can be applied directly to blood samples, and that was applied to 108 O. tsutsugamushi isolates. We found that this organism demonstrated a high rate of homologous recombination, a surprising finding given the intracellular life-style of this species. We also found that 25% of patients in our study were simultaneously infected with multiple sequence types, suggesting multiple infection caused by either multiple mite bites, or multiple strains co-existing within individual mites.
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影响因子：
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作者：
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