摘要

腹泻病原体艰难梭菌至少由六种不同的进化谱系组成。 RT017谱系是异常的，因为菌株仅表达毒素B，与来自产生毒素A和B的其他谱系的菌株以及偶尔的二元毒素相比。历史上，RT017最初是在亚洲报道的，但现在已在全球报道。我们使用全基因组测序和系统发育分析，调查了来自六大洲的动物和人类来源的277个RT017分离株的全球播散和群体结构模式，这些模式在1990年至2013年间分离出来。我们揭示了两种不同的均匀分裂的亚系（SL1和SL2）含有多个独立克隆扩展的艰难梭菌RT017。所有24种动物分离株都包含在SL1以及人分离株中，表明动物和人之间有潜在的传播。遗传分析揭示了抗生素抗性基因的过量表达。系统地理学分析显示了RT017的北美起源，正如最近出现的流行病RT027谱系所发现的。尽管只有一种毒素，RT017菌株已经从至少两个独立的来源平行进化，并且可以在各大洲之间轻松传播。

The diarrheal pathogen Clostridium difficile consists of at least six distinct evolutionary lineages. The RT017 lineage is anomalous, as strains only express toxin B, compared to strains from other lineages that produce toxins A and B and, occasionally, binary toxin. Historically, RT017 initially was reported in Asia but now has been reported worldwide. We used whole-genome sequencing and phylogenetic analysis to investigate the patterns of global spread and population structure of 277 RT017 isolates from animal and human origins from six continents, isolated between 1990 and 2013. We reveal two distinct evenly split sublineages (SL1 and SL2) of C. difficile RT017 that contain multiple independent clonal expansions. All 24 animal isolates were contained within SL1 along with human isolates, suggesting potential transmission between animals and humans. Genetic analyses revealed an overrepresentation of antibiotic resistance genes. Phylogeographic analyses show a North American origin for RT017, as has been found for the recently emerged epidemic RT027 lineage. Despite having only one toxin, RT017 strains have evolved in parallel from at least two independent sources and can readily transmit between continents.

http://jcm.asm.org/content/55/3/865.short