Microbiology Institute, Universidad San Francisco de Quito, Quito, Ecuador.
Public Health Institute, Oakland, California.
Microbiologyopen. 2019 Feb;8(2):e00643. doi: 10.1002/mbo3.643. Epub 2018 Jun 12.
Intestinal bacteria carry antimicrobial resistance (AMR) genes in mobile genetic elements which have the potential to spread to bacteria in other animal hosts including humans. In fecal matter, Escherichia coli can continue to multiply for 48 hr after being excreted, and in certain environments, E. coli survive long periods of time. It is unclear the extent to which AMR in E. coli changes in the environment outside of its host. In this study, we analyzed changes in the population structure, plasmid content, and AMR patterns of 30 E. coli isolates isolated from 6 chickens (cloacal swabs), and 30 E. coli isolates from fecal samples (from the same 6 chickens) after 24 hr of incubation. Clonality of isolates was screened using the fumC gene sequence and confirmed in a subset of isolates (n = 14) by multi-locus sequence typing. Major shifts in the population structure (i.e., sequence types) and antibiotic resistance patterns were observed among the numerically dominant E. coli isolates after 24 hr. Four E. coli clones isolated from the cloaca swabs and the corresponding fecal samples (after 24 hr incubation) showed different antibiotic resistance patterns. Our study reveals that fecal matter in the environment is an intermediate habitat where rapid and striking changes occur in E. coli populations and antibiotic resistance patterns.
肠道细菌在可移动的遗传因子中携带抗生素耐药性（AMR）基因，这些基因有可能传播到包括人类在内的其他动物宿主中的细菌。在粪便中，大肠杆菌在排出后 48 小时内可以继续繁殖，并且在某些环境中，大肠杆菌可以存活很长时间。目前尚不清楚大肠杆菌在宿主外的环境中 AMR 变化的程度。在这项研究中，我们分析了 30 株从 6 只鸡（泄殖腔拭子）中分离的大肠杆菌和 30 株从相同 6 只鸡的粪便样本中分离的大肠杆菌在 24 小时孵育后的种群结构、质粒含量和 AMR 模式的变化。使用 fumC 基因序列筛选分离株的克隆性，并在一部分分离株（n=14）中通过多位点序列分型进行确认。在 24 小时后，数量上占优势的大肠杆菌分离株的种群结构（即序列类型）和抗生素耐药模式发生了重大变化。从泄殖腔拭子和相应的粪便样本（孵育 24 小时后）中分离出的 4 株大肠杆菌克隆株显示出不同的抗生素耐药模式。我们的研究表明，环境中的粪便是一个中间栖息地，其中大肠杆菌种群和抗生素耐药模式会发生快速而显著的变化。
