摘要

由于在农场动物中广泛使用抗生素，经常报道多种抗生素抗性基因（ARG）在兽医粪便样品中具有高发病率。然而，ARGs在细菌中的分布和传播特点，特别是不同种类的多种抗生素耐药细菌（MARB），尚未得到很好的研究。通过应用高通量测序方法，我们的研究发现了牲畜粪便中的大量MARB库。埃希氏菌属，Myroides属，不动杆菌属，变形杆菌属，Ignatzschineria属，产碱菌属，普罗威登斯菌属和肠球菌属为主要的可培养MARB菌株，成分含量为40.6％-85.7％。从鸡粪分离物中选择33个MARB用于研究抗生素抗性的分子特征。共调查了61个ARG和18个移动遗传因子（MGE）。我们发现47个ARG在33个MARB分离株中广泛分布。每个分离物携带27-36个基因，负责对在临床或兽医环境中经常使用的八类抗生素的抗性。在所有33种MARB分离株中存在除链链霉素和万古霉素外的六类抗生素的ARG，发病率为80％-100％。在33个MARB中共有12个MGEs广泛分布，intI1，IS26，ISaba1和ISEcp1同时存在于100％的分离株中。另外，整合子内的9个基因盒和ISCR1在编码对不同抗生素类别的抗性的MARB分离株中检测到。这是第一份报告，揭示了多种ARGs，各种MGEs和ARG盒在鸡粪中不同种类的MARB分离物中的共同存在。结果显示，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/pii/S0269749117301963