Variations of the <i>Escherichia coli</i> population in the digestive tract of broilers

We explored the between-group and temporal variations in the intestinal <i>Escherichia coli</i> populations of broilers under experimental conditions, taking both antimicrobial resistance and virulence into consideration. Four replicates of 45 commercial chicks were reared in four animal facilities. On their first day of life (Day 0), they were orally inoculated with two extended-spectrum-cephalosporin-resistant (ESCR) <i>E. coli</i> (2.72 log₁₀ CFU of a <i>bla</i>_CMY-2- and 2.55 log₁₀ CFU of a <i>bla</i>_CTX-M-carrying <i>E. coli</i>). Faecal samples were then collected weekly and caecal samples were obtained from birds sacrificed on Days 21 or 42. The total, ESC-, ciprofloxacin- and gentamicin-resistant <i>E. coli</i> populations were enumerated on MacConkey (MC) and MC-supplemented media, and eight virulence-associated genes (VAGs) (<i>iroN, iutA, iss, ompT, hlyF, vat</i>, <i>frz_orf4</i>, and <i>fyuA</i>) were sought by PCR on isolates obtained on MC agar. The results showed significant between-group differences in the size of the resistant sub-populations and the presence of VAGs. Contrary to <i>bla</i>_CTX-M-positive strains, <i>bla</i>_CMY-positive strains persisted up to Day 42, but represented only a minor fraction of the total <i>E. coli</i> population. The ESC-, gentamicin- and ciprofloxacin-resistant populations decreased over time. Isolates obtained during the first week contained a mean of 5.1 VAGs. The percentages of some VAG profiles differed between faecal isolates on Day 41 and caecal isolates on Day 42. The fluctuations or differences between <i>E. coli</i> isolates according to group, age, and faecal or caecal origin need to be considered when designing experimental protocols and seeking to improve colibacillosis control. <b>RESEARCH HIGHLIGHTS</b>Temporal variations in the intestinal <i>E. coli</i> populations of broilers was studied.The antibiotic-resistant populations decreased over time.Virulence profiles differed between faecal isolates on Day 41 and caecal isolates on Day 42.Strains with the highest numbers of virulence genes were present during the first days. Temporal variations in the intestinal <i>E. coli</i> populations of broilers was studied. The antibiotic-resistant populations decreased over time. Virulence profiles differed between faecal isolates on Day 41 and caecal isolates on Day 42. Strains with the highest numbers of virulence genes were present during the first days.

本研究在实验条件下，探讨了肉鸡肠道大肠埃希菌（Escherichia coli）种群的组间差异与时间动态变化，同时考量了其抗菌耐药性与毒力特征。本研究设置4个重复单元，每单元包含45只商品代肉鸡雏鸡，将其饲养于4个动物实验设施中。雏鸡于出壳当日（第0天）经口接种两株超广谱头孢菌素耐药（extended-spectrum-cephalosporin-resistant, ESCR）大肠埃希菌：一株携带bla_CMY-2，接种量为2.72 log₁₀ CFU；另一株携带bla_CTX-M，接种量为2.55 log₁₀ CFU。随后每周采集粪便样本，并于第21天和第42天处死部分肉鸡，采集其盲肠样本。分别在麦康凯（MacConkey, MC）琼脂及添加抗生素的麦康凯培养基上计数总大肠埃希菌、超广谱头孢菌素耐药、环丙沙星耐药及庆大霉素耐药的大肠埃希菌种群；并通过聚合酶链式反应（PCR）对麦康凯琼脂上分离得到的菌株进行8种毒力相关基因（virulence-associated genes, VAGs）的检测，所涉基因为iroN、iutA、iss、ompT、hlyF、vat、frz_orf4及fyuA。研究结果显示，耐药亚种群的丰度及毒力相关基因的携带情况均存在显著的组间差异。与携带bla_CTX-M的菌株不同，携带bla_CMY的菌株可存活至第42天，但仅占总大肠埃希菌种群的极小比例。超广谱头孢菌素耐药、庆大霉素耐药及环丙沙星耐药的大肠埃希菌种群丰度随时间推移呈下降趋势。首周分离得到的菌株平均携带5.1个毒力相关基因。第41天粪便分离株与第42天盲肠分离株的部分毒力相关基因谱占比存在差异。在设计实验方案及优化鸡大肠杆菌病防控策略时，需考虑大肠埃希菌分离株根据分组、日龄以及粪便/盲肠来源不同所产生的波动或差异。**研究亮点**：肉鸡肠道大肠埃希菌种群的时间动态变化特征得到阐明；耐药性大肠埃希菌种群丰度随时间推移逐渐降低；第41天粪便分离株与第42天盲肠分离株的毒力基因谱存在差异；毒力基因数量最多的菌株于实验初期即可被分离得到。肉鸡肠道大肠埃希菌种群的时间动态变化特征得到阐明；耐药性大肠埃希菌种群丰度随时间推移逐渐降低；第41天粪便分离株与第42天盲肠分离株的毒力基因谱存在差异；毒力基因数量最多的菌株于实验初期即可被分离得到。

搜集汇总

背景与挑战

背景概述

该数据集研究了实验条件下肉鸡肠道中大肠杆菌种群的动态变化，重点关注抗菌素耐药性和毒力因素。研究发现，耐药大肠杆菌亚群随时间推移而减少，且毒力基因谱在粪便和盲肠样本中存在差异，高毒力菌株主要出现在早期阶段，为大肠杆菌病控制提供了实验依据。