Myers G S A, Mathews S A, Eppinger M, Mitchell C, O'Brien K K, White O R, Benahmed F, Brunham R C, Read T D, Ravel J, Bavoil P M, Timms P
Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
J Bacteriol. 2009 Dec;191(23):7225-33. doi: 10.1128/JB.00746-09. Epub 2009 Sep 11.
Zoonotic infections are a growing threat to global health. Chlamydia pneumoniae is a major human pathogen that is widespread in human populations, causing acute respiratory disease, and has been associated with chronic disease. C. pneumoniae was first identified solely in human populations; however, its host range now includes other mammals, marsupials, amphibians, and reptiles. Australian koalas (Phascolarctos cinereus) are widely infected with two species of Chlamydia, C. pecorum and C. pneumoniae. Transmission of C. pneumoniae between animals and humans has not been reported; however, two other chlamydial species, C. psittaci and C. abortus, are known zoonotic pathogens. We have sequenced the 1,241,024-bp chromosome and a 7.5-kb cryptic chlamydial plasmid of the koala strain of C. pneumoniae (LPCoLN) using the whole-genome shotgun method. Comparative genomic analysis, including pseudogene and single-nucleotide polymorphism (SNP) distribution, and phylogenetic analysis of conserved genes and SNPs against the human isolates of C. pneumoniae show that the LPCoLN isolate is basal to human isolates. Thus, we propose based on compelling genomic and phylogenetic evidence that humans were originally infected zoonotically by an animal isolate(s) of C. pneumoniae which adapted to humans primarily through the processes of gene decay and plasmid loss, to the point where the animal reservoir is no longer required for transmission.
人畜共患感染对全球健康构成的威胁日益增大。肺炎衣原体是一种主要的人类病原体，在人群中广泛传播，可引发急性呼吸道疾病，还与慢性病有关。肺炎衣原体最初仅在人类群体中被发现；然而，其宿主范围现已包括其他哺乳动物、有袋动物、两栖动物和爬行动物。澳大利亚树袋熊（Phascolarctos cinereus）广泛感染了两种衣原体，即考拉衣原体和肺炎衣原体。尚未有肺炎衣原体在动物与人类之间传播的报道；然而，另外两种衣原体，即鹦鹉热衣原体和流产衣原体，是已知的人畜共患病原体。我们使用全基因组鸟枪法对考拉肺炎衣原体菌株（LPCoLN）的1,241,024碱基对染色体和一个7.5千碱基对的隐蔽衣原体质粒进行了测序。包括假基因和单核苷酸多态性（SNP）分布的比较基因组分析，以及针对人类肺炎衣原体分离株的保守基因和SNP的系统发育分析表明，LPCoLN分离株位于人类分离株的基部。因此，基于令人信服的基因组和系统发育证据，我们提出人类最初是通过人畜共患途径被肺炎衣原体的动物分离株感染的，该分离株主要通过基因衰变和质粒丢失过程适应了人类，以至于传播不再需要动物宿主。
