摘要

       抗生素耐药基因（ARGs）在环境中的转移对人类和动物的健康都是一种威胁。然而，噬菌体通过转导途径对耐药基因的传播所起的作用却鲜有研究。在本研究中，我们从中国三个商业农场的猪粪中筛选出32种临床相关的精氨酸类型，以评估精氨酸在细菌和噬菌体中的存在，并进一步评估噬菌体对抗生素耐药性传播的贡献。我们发现噬菌体DNA中含有35.5%的目的ARG类型，100%的噬菌体DNA中含有sul1、blaTEM和ermB。细菌种群中最丰富的基因是ermB和fexA，而ermB是噬菌体中最丰富的基因。相比之下，两个种群的精氨酸含量均以floR最低。同时，本研究首次将噬菌体中ARGs的丰度与细菌的丰度比值作为噬菌体传递ARGs能力的评价指标。qnrA的比例最大（约为10-1），不同于最丰富的噬菌体ARG-ermB。此外，fexA的比值最低（约10-6），而不是floR。这些结果表明，单独使用ARGs丰度和检出率可能不适合综合判断噬菌体对抗生素耐药性传播的贡献。应用噬菌体发生率、绝对丰度和比值三个指标作为噬菌体环境ARG评价的预警和监测工具，是一个较为合适的模型。

       The transfer of antibiotic resistance genes (ARGs) in the environment is a threat to both human and animal health. However, the contribution of bacteriophages to the dissemination of resistance genes via transduction is rarely explored. In this study, we screened pig feces from three commercial farms in China for 32 clinically relevant ARG types to assess the presence of the ARG population in bacteria and bacteriophage and further to estimate the contribution of bacteriophages to the dissemination of antibiotic resistance. We found that bacteriophage DNA contained 35.5% of the target ARG types and sul1, bla_TEM and ermB were found in 100% of the phage DNA samples. The most abundant genes in the bacterial population were ermB and fexA whereas ermB was the most abundant in bacteriophage. In contrast, floR was the least abundant ARG in both populations. Also, the ratio index of the abundance of ARGs in bacteriophage and bacteria was firstly used in this study as an estimator of bacteriophage ability to transmit ARGs. The ratio for qnrA was the greatest (about 10^-1) and differed from the most abundant bacteriophage ARG ermB. In addition, fexA had the lowest ratio value (about 10^-6) and not floR. These results illustrate that ARGs abundance and detection rates used alone probably be not suitable for comprehensively judging the contribution of bacteriophage to the dissemination of antibiotic resistance. A more suitable model is the application of three indices; occurrence rate, absolute abundance in bacteriophage and the ratio value as warning and monitoring tools for environmental ARG assessments in bacteriophages.

        https://linkinghub.elsevier.com/retrieve/pii/S0269-7491(17)34918-7