Molecular Genetics Laboratory, Centre for Human Microbial Ecology, Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, PO Box #04, Faridabad, Haryana, 121001, India.
Division of Infectious Diseases, Department of Medicine, All India Institute of Medical Sciences, New Delhi, India.
Microb Ecol. 2019 Feb;77(2):546-557. doi: 10.1007/s00248-018-1228-7. Epub 2018 Jul 16.
Antimicrobial resistance (AMR) among bacterial species that resides in complex ecosystems is a natural phenomenon. Indiscriminate use of antimicrobials in healthcare, livestock, and agriculture provides an evolutionary advantage to the resistant variants to dominate the ecosystem. Ascendency of resistant variants threatens the efficacy of most, if not all, of the antimicrobial drugs commonly used to prevent and/or cure microbial infections. Resistant phenotype is very common in enteric bacteria. The most common mechanisms of AMR are enzymatic modifications to the antimicrobials or their target molecules. In enteric bacteria, most of the resistance traits are acquired by horizontal gene transfer from closely or distantly related bacterial population. AMR traits are generally linked with mobile genetic elements (MGEs) and could rapidly disseminate to the bacterial species through horizontal gene transfer (HGT) from a pool of resistance genes. Although prevalence of AMR genes among pathogenic bacteria is widely studied in the interest of infectious disease management, the resistance profile and the genetic traits that encode resistance to the commensal microbiota residing in the gut of healthy humans are not well-studied. In the present study, we have characterized AMR phenotypes and genotypes of five dominant commensal enteric bacteria isolated from the gut of healthy Indians. Our study revealed that like pathogenic bacteria, enteric commensals are also multidrug-resistant. The genes encoding antibiotic resistance are physically linked with MGEs and could disseminate vertically to the progeny and laterally to the distantly related microbial species. Consequently, the AMR genes present in the chromosome of commensal gut bacteria could be a potential source of resistance functions for other enteric pathogens.
在存在于复杂生态系统中的细菌物种中，抗生素耐药性（AMR）是一种自然现象。在医疗保健、畜牧业和农业中不加区分地使用抗生素，为耐药变体在生态系统中占据主导地位提供了进化优势。耐药变体的优势威胁到了大多数（如果不是全部）用于预防和/或治疗微生物感染的常用抗生素药物的疗效。耐药表型在肠细菌中非常常见。AMR 的最常见机制是对抗生素或其靶分子进行酶修饰。在肠细菌中，大多数耐药特性是通过来自密切或远缘细菌种群的水平基因转移获得的。AMR 特性通常与可移动遗传元件（MGE）相关联，并可通过来自抗性基因库的水平基因转移（HGT）迅速传播到细菌物种。虽然在传染病管理的利益相关下，广泛研究了致病细菌中 AMR 基因的流行情况，但对居住在健康人类肠道中的共生微生物群落的耐药谱和编码耐药性的遗传特征的研究还不够充分。在本研究中，我们对从健康印度人体内肠道分离出的五种主要共生肠细菌的 AMR 表型和基因型进行了表征。我们的研究表明，与致病细菌一样，肠共生菌也是多药耐药的。编码抗生素耐药性的基因与 MGE 物理相连，并可垂直传播给后代，也可横向传播给远缘微生物物种。因此，共生肠道细菌染色体中存在的 AMR 基因可能是其他肠病原体耐药功能的潜在来源。
