School of Life Sciences, Technical University of Munich, Freising, Germany.
Institute for Infectious Diseases and Zoonoses, LMU Munich, Munich, Germany.
J Appl Microbiol. 2022 Oct;133(4):2457-2465. doi: 10.1111/jam.15717. Epub 2022 Jul 26.
Antibiotic-resistant bacteria affect human and animal health. Hence, their environmental spread represents a potential hazard for mankind. Livestock farming is suspected to be a key factor for spreading antibiotic resistance; consumers expect organic farming to imply less environmental health risk. This study aimed to assess the role of manure from organic and conventional farms for spreading antimicrobial resistance (AMR) genes.
AMR-genes-namely tet(A), tet(B), tet(M), sul2 and qacE/qacEΔ1 (potentially associated with multiresistance) were quantified by qPCR. Antimicrobial use during the study period was qualitatively assessed from official records in a binary mode (yes/no). Median concentrations were between 6.44 log copy-equivalents/g for tet(A) and 7.85 for tet(M) in organic liquid manure, and between 7.48 for tet(A) and 8.3 for sul2 in organic farmyard manure. In conventional manure, median concentrations were 6.67 log copy-equivalents/g for sul2, 6.89 for tet(A), 6.77 for tet(B) and 8.36 for tet(M). Integron-associated qac-genes reached median concentrations of 7.06 log copy-equivalents/g in organic liquid manure, 7.13 in conventional manure and 8.18 in organic farmyard manure. The use of tetracyclines or sulfonamides increased concentrations of tet(A) and tet(M), or of sul2, respectively. Comparing farms that did not apply tetracyclines during the study, the relative abundance of tet(A) and tet(M) was still higher for conventional piggeries than for organic ones.
Relative abundances of AMR genes were higher in conventional farms, compared to organic ones. Antibiotic use was linked to the relative abundance of AMR-genes. However, due to the bacterial load, absolute concentrations of AMR-genes were comparable between fertilizers of organic and conventional farms.
To our knowledge, this is the first absolute quantification of AMR-genes in manure from organic farms. Our study underlines the importance of long-term reduction in the use of antimicrobial agents in order to minimize antibiotic resistance.
抗生素耐药细菌影响人类和动物健康。因此，它们在环境中的传播对人类构成潜在威胁。畜牧业被怀疑是传播抗生素耐药性的关键因素；消费者期望有机农业的环境健康风险较小。本研究旨在评估来自有机和常规农场的粪便在传播抗微生物药物耐药性（AMR）基因方面的作用。
通过 qPCR 定量测定 AMR 基因 - 即 tet(A)、tet(B)、tet(M)、sul2 和 qacE/qacEΔ1（可能与多药耐药性相关）。在二元模式（是/否）下，从官方记录中定性评估研究期间的抗菌药物使用情况。有机液体粪便中 tet(A)的中位数浓度在 6.44 log 拷贝等价物/g 之间，而有机粪肥中 tet(M)的中位数浓度在 7.85 之间。在常规粪便中，sul2 的中位数浓度为 6.67 log 拷贝等价物/g，tet(A)为 6.89，tet(B)为 6.77，tet(M)为 8.36。整合子相关的 qac 基因在有机液体粪便中的中位数浓度为 7.06 log 拷贝等价物/g，在常规粪便中的中位数浓度为 7.13，在有机粪肥中的中位数浓度为 8.18。四环素或磺胺类药物的使用增加了 tet(A)和 tet(M)或 sul2 的浓度。比较研究期间未使用四环素的农场，常规养猪场的 tet(A)和 tet(M)相对丰度仍高于有机养猪场。
与有机农场相比，常规农场的 AMR 基因相对丰度更高。抗生素的使用与 AMR 基因的相对丰度有关。然而，由于细菌负荷，有机和常规农场肥料中 AMR 基因的绝对浓度相当。
据我们所知，这是首次对有机农场粪便中的 AMR 基因进行绝对定量。我们的研究强调了长期减少抗菌药物使用以最小化抗生素耐药性的重要性。
