Institute of Pathology, University of Bern, Bern, Switzerland.
Adv Exp Med Biol. 2019;1197:97-105. doi: 10.1007/978-3-030-28524-1_8.
The colonization of body surfaces, notably of the intestine, by a complex microbiota is generally highly mutualistic, where vital functions are provided by the commensal microbiota to the host, including the synthesis of vitamins, the degradation of complex polysaccharides into small chain fatty acids (which are essential for the maintenance of the intestinal epithelial barrier), and, finally, the outcompetition of pathogens that accidentally gain access to the body ("colonization resistance") (Chow et al. 2011; Backhed 2005). However, under certain conditions, such as changes of environmental factors in a genetically predisposed host, some of these normally symbiotic bacteria may act as pathogens and induce pathologies. Hence, the term "pathobionts" was coined for these bacterial species with ambiguous biological properties (Round et al. 2009).
人体表面（尤其是肠道）被复杂的微生物群落定植通常是高度互利的，共生微生物群落为宿主提供了重要功能，包括合成维生素、将复杂多糖降解为短链脂肪酸（这对于维持肠道上皮屏障至关重要），以及最终竞争定植于机体的病原体（“定植抗力”）（Chow 等人，2011 年；Backhed，2005 年）。然而，在某些情况下，例如遗传易感性宿主的环境因素发生变化，这些正常共生的细菌中的一些可能会充当病原体并引发疾病。因此，对于这些具有模糊生物学特性的细菌物种，术语“条件致病菌”被创造出来（Round 等人，2009 年）。
