Faculté de Pharmacie, Laboratoire de Bactériologie-Virologie, Université Montpellier 1, 34093 Montpellier Cedex 5, France.
BMC Microbiol. 2009 Dec 18;9:267. doi: 10.1186/1471-2180-9-267.
Ochrobactrum anthropi is a versatile bacterial species with strains living in very diverse habitats. It is increasingly recognized as opportunistic pathogen in hospitalized patients. The population biology of the species particularly with regard to the characteristics of the human isolates is being investigated. To address this issue, we proposed a polyphasic approach consisting in Multi-Locus Sequence Typing (MLST), multi-locus phylogeny, genomic-based fingerprinting by pulsed-field gel electrophoresis (PFGE) and antibiotyping.
We tested a population of 70 O. anthropi clinical (n = 43) and environmental (n = 24) isolates as well as the type strain O. anthropi ATCC49188T and 2 strains of Ochrobactrum lupini and Ochrobactrum cytisi isolated from plant nodules. A Multi-Locus Sequence Typing (MLST) scheme for O. anthropi is proposed here for the first time. It was based on 7 genes (3490 nucleotides) evolving mostly by neutral mutations. The MLST approach suggested an epidemic population structure. A major clonal complex corresponded to a human-associated lineage since it exclusively contained clinical isolates. Genomic fingerprinting separated isolates displaying the same sequence type but it did not detect a population structure that could be related to the origin of the strains. None of the molecular method allowed the definition of particular lineages associated to the host-bacteria relationship (carriage, colonisation or infection). Antibiotyping was the least discriminative method.
The results reveal a human-associated subpopulation in our collection of strains. The emergence of this clonal complex was probably not driven by the antibiotic selective pressure. Therefore, we hypothesise that the versatile species O. anthropi could be considered as a human-specialized opportunistic pathogen.
食酸菌是一种多功能的细菌物种，其菌株生活在非常多样化的栖息地中。它越来越被认为是住院患者的机会性病原体。该物种的种群生物学，特别是关于人类分离株的特征，正在被研究。为了解决这个问题，我们提出了一种多相方法，包括多位点序列分型（MLST）、多位点系统发育、基于脉冲场凝胶电泳（PFGE）的基因组指纹图谱和抗生素型分析。
我们测试了一个由 70 株食酸菌临床（n = 43）和环境（n = 24）分离株以及模式株食酸菌 ATCC49188T 和 2 株从植物根瘤中分离的食黄杆菌和黄杆菌组成的群体。这里首次提出了一种用于食酸菌的多基因序列分型（MLST）方案。它是基于 7 个基因（3490 个核苷酸）的进化，主要通过中性突变。MLST 方法表明存在一种流行的种群结构。一个主要的克隆复合体对应于一个与人类相关的谱系，因为它只包含临床分离株。基因组指纹图谱将表现出相同序列类型的分离株分开，但它没有检测到与菌株来源相关的种群结构。没有任何分子方法可以定义与宿主-细菌关系（携带、定植或感染）相关的特定谱系。抗生素型分析是最具鉴别力的方法。
这些结果揭示了我们收集的菌株中存在一个与人类相关的亚群。这个克隆复合体的出现可能不是由抗生素的选择压力驱动的。因此，我们假设多功能的食酸菌可以被认为是一种人类特化的机会性病原体。
