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Lancet Infect Dis:发现导致莱姆病的新菌种

  1. 莱姆病
  2. Borrelia mayonii
  3. 伯氏疏螺旋体
  4. Borrelia burgdorferi

来源:生物谷 2016-02-13 11:20

在一项新的研究中,美国研究人员发现一种新的导致人们患上莱姆病的细菌,这种新的细菌暂时被命名为Borrelia mayonii。

2016年2月11日/生物谷BIOON/--在一项新的研究中,美国梅约诊所与美国疾病控制与防御中心(CDC)、来自明尼苏达州、北达科他州和威斯康星州的卫生官员合作,发现一种新的导致人们患上莱姆病(Lyme disease)的细菌。这种新的细菌暂时被命名为Borrelia mayonii。在此之前,在北美洲被认为导致莱姆病的唯一细菌是伯氏疏螺旋体(Borrelia burgdorferi)。相关研究结果于2016年2月5日在线发表在The Lancet Infectious Diseases期刊上,论文标题为“Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study”。

在这项研究中,梅约诊所研究人员利用聚合酶链式反应(PCR)方法对2003~2014年的美国病人样品进行测试来寻找莱姆病的病因。从2012~2014年,他们从来自明尼苏达州、北达科他州和威斯康星州的9000例样品中的6例样品中观察到不同寻常的测试结果。

论文第一作者、梅约诊所临床寄生虫学实验室主任Bobbi Pritt博士说,“利用一种被称作熔点温度分析的方法在实验室中进行测试,我们检测到6例样品的PCR测试结果明显不同于伯氏疏螺旋体。作为梅约诊所的标准实验室,梅约医学实验室过去年十多年来已测试了来自美国全部50个州的10万例以上的病人样品,但是我们最近只检测到B. mayonii存在的证据。”

基于这些发现,研究人员认为这种有机体可能只是最近出现在美国上中西部地区。Pritt博士补充道,“这种细菌可能已存在了更长的时间,但是水平如此之低以至于它未被检测出来。”

正如伯氏疏螺旋体一样,研究人员认为B. mayonii也是通过一种被感染的黑腿壁虱(有时也被称作鹿蜱)的叮咬而被传播到人体中。莱姆病的典型症状包括发热、头疼、湿疹、脖子疼以及后期出现的关节炎。然而,不同于伯氏疏螺旋体的是,B. mayonii导致的疾病似乎与困乏、呕吐、弥漫性皮疹,以及血液中更高水平的细菌相关联。

利用当前可购买的美国食品药品管理局(FDA)批准的莱姆病测试方法,B. mayonii感染病人的测试结果也是阳性的。在某些情形下,B. mayonii细菌也可能在血液涂片中观察到。Pritt博士注意到,“利用梅约诊所开发的检测莱姆病细菌DNA的PCR测试方法,就能够特异性地鉴别出这种有机体。”

在本项研究中,为了治疗由B. mayonii导致的这种疾病,病人服用经常用来治疗伯氏疏螺旋体导致的莱姆病的抗生素后,也完全康复了。美国CDC建议正在治疗B. mayonii感染病人的医疗护理机构也应当遵守美国传染性协会制定的抗生素使用指南。

Pritt博士补充道,“目前,还没有证据证实B. mayonii也存在于美国上中西部地区之外的地方。然而,鉴于莱姆病和其他蜱携带疾病也在美国东北部广泛存在,公众应当继续对蜱叮咬采取推荐的预防措施。”(生物谷 Bioon.com)

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doi:10.1016/S1473-3099(15)00464-8

Identification of a novel pathogenic Borrelia species causing Lyme borreliosis with unusually high spirochaetaemia: a descriptive study

Bobbi S PrittxBobbi S Pritt et el.

Background
Lyme borreliosis is the most common tick-borne disease in the northern hemisphere. It is a multisystem disease caused by Borrelia burgdorferi sensu lato genospecies and characterised by tissue localisation and low spirochaetaemia. In this study we aimed to describe a novel Borrelia species causing Lyme borreliosis in the USA.

Methods
At the Mayo clinic, from 2003 to 2014, we tested routine clinical diagnostic specimens from patients in the USA with PCR targeting the oppA1 gene of B burgdorferi sensu lato. We identified positive specimens with an atypical PCR result (melting temperature outside of the expected range) by sequencing, microscopy, or culture. We collected Ixodes scapularis ticks from regions of suspected patient tick exposure and tested them by oppA1 PCR.

Findings
100 545 specimens were submitted by physicians for routine PCR from Jan 1, 2003 to Sept 30, 2014. From these samples, six clinical specimens (five blood, one synovial fluid) yielded an atypical oppA1 PCR product, but no atypical results were detected before 2012. Five of the six patients with atypical PCR results had presented with fever, four had diffuse or focal rash, three had symptoms suggestive of neurological inclusion, and two were admitted to hospital. The sixth patient presented with knee pain and swelling. Motile spirochaetes were seen in blood samples from one patient and cultured from blood samples from two patients. Among the five blood specimens, the median oppA1 copy number was 180 times higher than that in 13 specimens that tested positive for B burgdorferi sensu stricto during the same time period. Multigene sequencing identified the spirochaete as a novel B burgdorferi sensu lato genospecies. This same genospecies was detected in ticks collected at a probable patient exposure site.

Interpretation
We describe a new pathogenic Borrelia burgdorferi sensu lato genospecies (candidatus Borrelia mayonii) in the upper midwestern USA, which causes Lyme borreliosis with unusually high spirochaetaemia. Clinicians should be aware of this new B burgdorferi sensu lato genospecies, its distinct clinical features, and the usefulness of oppA1 PCR for diagnosis.

Funding
US Centers for Disease Control and Prevention Epidemiology and Laboratory Capacity for Infectious Diseases (ELC) Cooperative Agreement and Mayo Clinic Small Grant programme.

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