摘要

       由于在农场动物中广泛使用抗生素，经常报告多种抗生素抗性基因 (ARG) 在兽医粪便样本中具有很高的流行率。然而，ARGs在细菌间，特别是在不同种类的多重耐药菌（MARB）间的分布和传播特征还没有得到很好的探索。通过应用高通量测序方法，我们的研究在牲畜粪便中发现了一个巨大的 MARB 库。埃希氏菌属、Myroides 属、不动杆菌属、变形杆菌属、Ignatzschineria 属、产碱杆菌属、普罗维登斯氏菌属和肠球菌属是主要的可培养 MARB，组成为 40.6%–85.7%。从鸡粪分离物中选择了 33 个 MARB 用于研究抗生素抗性的分子特征。总共研究了 61 个 ARG 和 18 个移动遗传元件 (MGE)。我们发现 47 个 ARG 广泛分布在 33 个 MARB 分离株中。每个分离株携带 27-36 个基因，负责对临床或兽医环境中常用的八类抗生素产生抗性。所有 33 株 MARB 分离株中都存在除链霉菌素和万古霉素以外的六类抗生素的 ARG，患病率为 80%–100%。总共 12 个 MGEs 广泛分布在 33 个 MARB 中，intI1、IS26、ISaba1 和 ISEcp1 同时存在于 100% 的分离株中。此外，在编码对不同抗生素类别的抗性的 MARB 分离株中检测到整合子和 ISCR1 内的 9 个基因盒。这是第一份揭示鸡粪中不同种类的个体 MARB 分离株中多种 ARG、各种 MGE 和 ARG 盒普遍共存的报告。结果表明，ARGs 通过牲畜粪便传播给人类的风险比我们预期的要高得多。

       Diverse antibiotic-resistance genes (ARGs) are frequently reported to have high prevalence in veterinary manure samples due to extensive use of antibiotics in farm animals. However, the characteristics of the distribution and transmission of ARGs among bacteria, especially among different species of multiple antibiotic-resistant bacteria (MARB), have not been well explored. By applying high-throughput sequencing methods, our study uncovered a vast MARB reservoir in livestock manure. The genera Escherichia, Myroides, Acinetobacter, Proteus, Ignatzschineria, Alcaligenes, Providencia and Enterococcus were the predominant cultivable MARB, with compositions of 40.6%–85.7%. From chicken manure isolates, 33 MARB were selected for investigation of the molecular characteristics of antibiotic resistance. A total of 61 ARGs and 18 mobile genetic elements (MGEs) were investigated. We found that 47 ARGs were widely distributed among the 33 MARB isolates. Each isolate carried 27–36 genes responsible for resistance to eight classes of antibiotics frequently used in clinic or veterinary settings. ARGs to the six classes of antibiotics other than streptogramins and vancomycin were present in all 33 MARB isolates with a prevalence of 80%–100%. A total of 12 MGEs were widely distributed among the 33 MARB, with intI1, IS26, ISaba1, and ISEcp1 simultaneously present in 100% of isolates. In addition, 9 gene cassettes within integrons and ISCR1 were detected among MARB isolates encoding resistance to different antibiotic classes. This is the first report revealing the general co-presence of multiple ARGs, various MGEs and ARG cassettes in different species of individual MARB isolates in chicken manure. The results highlight a much higher risk of ARGs spreading through livestock manure to humans than we expected.

https://www.sciencedirect.com/science/article/abs/pii/S0269749117301963