Lira Felipe, Berg Gabriele, Martínez José L
Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas, Madrid, Spain.
Institute of Environmental Biotechnology, Graz University of Technology, Graz, Austria.
Front Microbiol. 2017 Nov 9;8:2190. doi: 10.3389/fmicb.2017.02190. eCollection 2017.
Most studies on bacterial virulence focus on the pathogen itself. However, it is important to recall that the in-host behavior and the virulence of bacterial pathogens constitute a complex situation that depends on both the microorganisms and the infected host. While healthy people (the community) is infected by classical pathogenic microorganisms, able to cope with the anti-infection defenses of the host, in the case of people with basal diseases, debilitated or immunodepressed, the range of pathogens able to cause infection is wider and includes the so-named opportunistic pathogens, which lack the inherent ability to cause disease in healthy hosts and rarely produce infections in the community. Some of the most relevant opportunistic pathogens, as , have an environmental origin and, in occasions, present interesting biotechnological properties. Consequently, it is important knowing whether isolates recovered from infections constitute a specific phylogenetic branch that has evolved toward acquiring a virulent phenotype as it happens in the case of classical pathogens or rather, any member of this bacterial species is capable of producing infection and its pathogenic behavior is mainly a consequence of the host situation. To address this question, we analyzed a set of environmental and clinical strains. Our results indicate that this opportunistic pathogen presents a large core genome and that the distribution of genes in general, and of known virulence determinants in particular, is similar among environmental and clinical isolates. The majority of genes not belonging to the core genome are present in just one or two of the analyzed strains. This indicates that, more than speciation into different lineages (virulent and environmental), the evolution of is based in the strain-specific acquisition of genes, likely involved in the adaptation of this bacterial species to different microniches. In addition, both environmental and clinical isolates present low susceptibility to several antimicrobials. Altogether our results support that does not present a specific evolutionary branch toward virulence and most likely infection is mainly the consequence of the impaired anti-infective response of the infected patients.
大多数关于细菌毒力的研究都集中在病原体本身。然而，必须记住的是，细菌病原体在宿主体内的行为及其毒力构成了一种复杂的情况，这既取决于微生物，也取决于受感染的宿主。当健康人群（社区）被能够应对宿主抗感染防御的经典致病微生物感染时，对于患有基础疾病、身体虚弱或免疫抑制的人来说，能够引起感染的病原体范围更广，包括所谓的机会性病原体，这些病原体在健康宿主中缺乏引起疾病的内在能力，在社区中很少引起感染。一些最相关的机会性病原体，如 ，起源于环境，有时还具有有趣的生物技术特性。因此，了解从感染中分离出的 菌株是否构成一个特定的系统发育分支，该分支已朝着获得毒力表型进化，就像经典病原体那样，或者该细菌物种的任何成员是否都能够引起感染，其致病行为主要是否是宿主状况的结果，这一点很重要。为了解决这个问题，我们分析了一组环境和临床 菌株。我们的结果表明，这种机会性病原体具有一个大的核心基因组，并且一般基因的分布，特别是已知毒力决定因素的分布，在环境和临床分离株中相似。大多数不属于 核心基因组的基因仅存在于一两个分析菌株中。这表明， 的进化并非形成不同的谱系（有毒力的和环境的），而是基于菌株特异性的基因获取，这些基因可能参与了该细菌物种对不同微生态位的适应。此外，环境和临床分离株对几种抗菌药物的敏感性都较低。我们的结果总体上支持 不存在朝着毒力发展的特定进化分支，感染很可能主要是受感染患者抗感染反应受损的结果。
