Department of Poultry Science, Mississippi State Universitygrid.260120.7, Starkville, Mississippi, USA.
Virginia-Maryland College of Veterinary Medicine, Blacksburg, Virginia, USA.
Microbiol Spectr. 2021 Dec 22;9(3):e0083421. doi: 10.1128/Spectrum.00834-21. Epub 2021 Dec 8.
Avian pathogenic Escherichia coli (APEC) causes significant economic and welfare concerns to the broiler industry. For several decades, prophylactic supplementation of antimicrobial growth promoters was the primary method to control APEC; however, the recent shift to no antibiotics ever (NAE) production has increased colibacillosis incidence. The objectives of this study were to determine the influence of season, flock age, and sample type on the prevalence and virulence of E. coli and to identify the serogroups and antimicrobial susceptibility of virulent and nonvirulent E. coli in NAE broiler farms. Litter, feces, cloacal swabs, and tracheal swabs were collected from 4 NAE farms during spring and summer seasons, and E. coli was isolated and confirmed by PCR. Confirmed E. coli isolates were tested for 5 APEC-virulence-associated genes (VAGs) using quantitative PCR (qPCR). Further, E. coli isolates with all five VAGs (100 isolates) and E. coli isolates without any VAGs (87 isolates) were screened against 11 antimicrobials through Kirby-Bauer disk diffusion assay, and their serogroups were tested using PCR. Data were analyzed using the GLIMMIX procedure of SAS 9.4, and statistical significance was determined at a value of 0.05. Overall, the prevalence of E. coli was not affected by season, flock age, or sample type. However, the prevalence of all tested VAGs decreased from spring to summer (0.002). The frequency of resistance was highest for tetracycline, and serogroups O8 (31%) and O78 (11%) were most frequent in virulent E. coli. In conclusion, there is a high prevalence of virulent E. coli in NAE farms, especially in the spring season. Avian pathogenic Escherichia coli causes one of the most detrimental bacterial diseases to the United States poultry industry, colibacillosis. Colibacillosis leads to decreased performance, early mortality, and subsequent production loss. Previously, colibacillosis was largely mitigated by the use of antimicrobial growth promoters. Due to concerns about antimicrobial resistance, the use of these promoters has been largely removed from the broiler industry. With recent shifts in the poultry industry to NAE broiler production, there is an increase in bacterial disease and mortality. We do not know how this shift to NAE affects APEC prevalence within broiler farms. Therefore, in the current study, we attempted to assess the prevalence and virulence of E. coli within an antibiotic-free broiler environment, assessed antimicrobial susceptibility, and identified the serogroups of virulent and nonvirulent E. coli.
禽流感大肠杆菌 (APEC) 给肉鸡产业带来了重大的经济和福利问题。几十年来，预防性添加抗菌生长促进剂一直是控制 APEC 的主要方法；然而，最近向无抗生素养殖的转变增加了大肠杆菌病的发病率。本研究的目的是确定季节、鸡群年龄和样本类型对大肠杆菌流行率和毒力的影响，并确定无抗生素养殖肉鸡场中毒力和非毒力大肠杆菌的血清群和抗菌药物敏感性。在春季和夏季，从 4 个无抗生素养殖肉鸡场采集垫料、粪便、泄殖腔拭子和气管拭子，并通过 PCR 分离和确认大肠杆菌。使用定量 PCR (qPCR) 检测确认的大肠杆菌分离株中 5 种 APEC 毒力相关基因 (VAGs)。此外，通过 Kirby-Bauer 圆盘扩散试验筛选具有所有 5 种 VAG 的大肠杆菌分离株（100 株）和不具有任何 VAG 的大肠杆菌分离株（87 株），针对 11 种抗菌药物进行筛选，并通过 PCR 测试其血清群。使用 SAS 9.4 的 GLIMMIX 过程分析数据， 并在 0.05 水平上确定统计显著性。总体而言，大肠杆菌的流行率不受季节、鸡群年龄或样本类型的影响。然而，所有测试的 VAG 的流行率从春季到夏季呈下降趋势（0.002）。四环素的耐药率最高，毒力大肠杆菌中血清群 O8（31%）和 O78（11%）最为常见。总之，无抗生素养殖肉鸡场中存在高毒力大肠杆菌的流行率，尤其是在春季。 禽流感大肠杆菌是美国家禽业最具危害性的细菌性疾病之一，大肠杆菌病。大肠杆菌病导致性能下降、早期死亡和随后的生产损失。以前，通过使用抗菌生长促进剂，大肠杆菌病在很大程度上得到了缓解。由于对抗菌药物耐药性的担忧，这些促进剂已在肉鸡行业中大量去除。随着家禽业向无抗生素养殖肉鸡生产的转变，细菌性疾病和死亡率有所增加。我们不知道这种向无抗生素养殖的转变如何影响肉鸡场内 APEC 的流行率。因此，在当前研究中，我们试图评估无抗生素养殖肉鸡环境中 E. coli 的流行率和毒力，评估抗菌药物敏感性，并确定毒力和非毒力 E. coli 的血清群。
