Comprehensive Analysis of Antimicrobial, Heavy Metal, and Pesticide Residues in Commercial Organic Fertilizers and Their Correlation with Tigecycline-Resistant tet(X)-Variant Genes.
Comprehensive Analysis of Antimicrobial, Heavy Metal, and Pesticide Residues in Commercial Organic Fertilizers and Their Correlation with Tigecycline-Resistant tet(X)-Variant Genes.
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DOI：
10.1128/spectrum.04251-22
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发表时间：
2023-03-14
影响因子：
3.7
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中科院分区：
文献类型：
--
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随着中国畜牧业饲料中抗生素添加剂禁令的发布，确定新发现的抗替格列汀泰特（X）变异基因传播的潜在驱动因素非常重要。在这里，我们调查了来自中国9个省的94个商业有机肥料样品中重金属、抗菌剂和农药残留与泰特（X）变异基因相对丰度之间的相关性。共检测出5种重金属（汞、铅、砷、铬和镉）、10种抗菌剂和18种农药。在39例（41.5%）样本中检测到泰特（X）变异基因，包括泰特（X）/（X2）、泰特（X3）、泰特（X4）、泰特（X5）和泰特（X6）。尽管未从这些样品中分离到携带泰特（X）变体的细菌，但携带泰特（X4）的质粒可被外源性大肠杆菌捕获。相关分析表明，除抗菌剂外，重金属与泰特（X）变异基因的相对丰度呈显著正相关，尤其是泰特（X3）和泰特（X4）（R = 0.346 ~ 0.389，P < 0.001）。这种相关性归因于泰特（X3）/泰特（X4）基因在同一质粒上的共选择性以及重金属亚抑制浓度对携带泰特（X3）/泰特（X4）质粒的接合促进作用。重金属增加了细菌外膜的通透性，上调了携带泰特（X）变体质粒上的IV型分泌系统（T4 SS）编码基因的转录，从而提高了细菌接合率。综上所述，我们的研究结果表明，重金属可能在动物粪便相关环境中传播泰特（X）变异基因方面发挥重要作用。抗菌素耐药基因（ARG）被认为是一种新的环境污染物。我国大部分动物粪便通常被制成商品有机肥料，如果将携带有临床意义的抗菌素耐药（AMR）基因的肥料应用于农田，将对农田土壤和农产品构成威胁。本研究表明，重金属可能在可转移的替加环素耐药基因[泰特（X3）和泰特（X4）]的传递中发挥重要作用。其机制是重金属对同一质粒上的泰特（X3）/泰特（X4）基因产生共选择效应，可以提高携带泰特（X3）/泰特（X4）的质粒的接合能力。重金属的结合促进浓度均低于国家肥料标准中规定的最大限值，表明泰特（X3）/泰特（X4）基因在畜禽粪便相关环境中具有较高的传播风险。本研究结果将为今后制定有效措施减少AMR传播提供科学依据。
With the issue of the antimicrobial additive ban in feed in Chinese animal husbandry, it is important to determine the potential drivers of the spread of the newly discovered tigecycline-resistant tet(X)-variant genes. Here, we investigated the correlations between residues of heavy metals, antimicrobials, and pesticides and the relative abundance of tet(X)-variant genes in 94 commercial organic-fertilizer samples collected from 9 Chinese provinces. A total of 5 heavy metals (mercury, lead, arsenic, chromium, and cadmium), 10 antimicrobials, and 18 pesticides were detected. The tet(X)-variant genes, including tet(X)/(X2), tet(X3), tet(X4), tet(X5), and tet(X6) were detected in 39 (41.5%) samples. Although tet(X)-variant-carrying bacteria were not isolated from these samples, the tet(X4)-carrying plasmids could be captured by exogenous Escherichia coli. Correlation analysis revealed that heavy metals, other than antimicrobials, showed a significant positive association with the relative abundance of the tet(X)-variant genes, especially tet(X3) and tet(X4) (R = 0.346 to 0.389, P < 0.001). The correlation was attributed to the coselection of the tet(X3)/tet(X4) gene on the same plasmid and the conjugation-promoting effect of tet(X3)/tet(X4)-carrying plasmids by subinhibitory concentrations of heavy metals. The heavy metals increased the permeability of the bacterial outer membrane and upregulated the transcription of type IV secretion system (T4SS)-encoding genes on tet(X)-variant-carrying plasmids, therefore enhancing the bacterial conjugation rates. Taken together, our findings have indicated that heavy metals may play an important role in spreading tet(X)-variant genes within the animal manure-related environment. IMPORTANCE An antimicrobial resistance gene (ARG) is considered a novel contaminant for the environment. Most animal feces are usually made into commercial organic fertilizers in China and will pose a threat to the farmland soil and agricultural product if fertilizers harboring clinically significant antimicrobial-resistant (AMR) genes are applied on farmland. This study has indicated that heavy metals may play an important role in the transmission of transferable tigecycline resistance genes [tet(X3) and tet(X4)]. The mechanism was that heavy metals posed a coselection effect of the tet(X3)/tet(X4) gene on the same plasmid and could increase the conjugation ability of tet(X3)/tet(X4)-carrying plasmids. The conjugation-promoting concentrations of heavy metals are lower than the maximal limits defined in the national standard for fertilizers, indicating a high transmission risk of tet(X3)/tet(X4) genes within the animal manure-related environment. The findings in this study will provide scientific evidence for the future development of effective measures to reduce AMR dissemination.
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影响因子：
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作者：
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影响因子：
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