摘要
      病原体中抗生素耐药性基因的快速传播正在威胁人类健康。整合子允许细菌整合和表达外源基因，促进ARGs在环境中的水平转移。食用生蔬菜是人类接触环境ARGs的一种途径。然而，很少有研究关注生蔬菜内生菌中与整合素相关的ARGs。在此，基于qPCR和克隆文库的方法，我们定量了6种常见生蔬菜内生菌中整合酶基因的丰度，并分析了1类整合子中抗性基因盒的多样性和含量。结果表明，与2类和3类整合子整合酶基因相比，1类整合子的整合酶基因最为普遍（1-2个数量级，P<0.05）。黄瓜内生菌的整合酶绝对丰度高于其他蔬菜，而卷心菜和黄瓜内生真菌的细菌丰度最高。检测到32个独特的抗性基因盒，其中大多数与编码β-内酰胺和氨基糖苷抗性的基因有关。抗生素耐药基因盒占功能注释基因盒的52.5%，blaTEM-157和aadA2是最常检测到的耐药盒。此外，胡萝卜内生菌在1类整合子中具有最高比例的抗生素抗性基因盒。总之，这些结果为生蔬菜内生菌中整合子获得的抗性基因提供了深入的视角，并强调了ARGs通过食物链传播的潜在健康风险。
Abstract
Rapid spread of antibiotic resistance genes (ARGs) in pathogens is threatening human health. Integrons allow bacteria to integrate and express foreign genes, facilitating horizontal transfer of ARGs in environments. Consumption of raw vegetables represents a pathway for human exposure to environmental ARGs. However, few studies have focused on integron-associated ARGs in the endophytes of raw vegetables. Here, based on the approach of qPCR and clone library, we quantified the abundance of integrase genes and analyzed the diversity and contents of resistance gene cassettes in class 1 integrons from the endophytes of six common raw vegetables. The results revealed that integrase genes for class 1 integron were most prevalent compared with class 2 and class 3 integron integrase genes (1–2 order magnitude, P < 0.05). The cucumber endophytes harbored a higher absolute abundance of integrase genes than other vegetables, while the highest bacterial abundance was detected in cabbage and cucumber endophytes. Thirty-two unique resistance gene cassettes were detected, the majority of which were associated with the genes encoding resistance to beta-lactam and aminoglycoside. Antibiotic resistance gene cassettes accounted for 52.5 % of the functionally annotated gene cassettes, and blaTEM-157 and aadA2 were the most frequently detected resistance cassettes. Additionally, carrot endophytes harbored the highest proportion of antibiotic resistance gene cassettes in the class 1 integrons. Collectively, these results provide an in-depth view of acquired resistance genes by integrons in the raw vegetable endophytes and highlight the potential health risk of the transmission of ARGs via the food chain.

https://www.sciencedirect.com/science/article/pii/S0147651322011228