摘要
      肠道菌群是抗生素耐药性发展的最重要环境之一，因为其细菌种类繁多。选择一种优秀的医学模式生物热带爪蟾，研究抗生素耐药性基因（ARGs）在罗红霉素（ROX）和土霉素（OTC）单次或联合暴露的肠道细菌群落中的传播。在热带爪蟾的肠道中检测到17个抗性基因（tetA、tetB、tetE、tetM、tet0、tetS、tetX、ermF、msrA、mefA、ereA、ereB、mphA、mphB、intI1、intI2、intI3），这些基因生活在三个试验罐（ROX罐、OTC罐、ROX+OTC罐）和一个空白罐中20天。结果表明，总ARGs的相对丰度在单一胁迫下明显增加，但在复合胁迫下降低，其中编码大环内酯类抗生素外排泵（msrA）、磷酸酶（mphB）和整合素（intI2，intI3）的基因最为敏感。在AFM扫描的帮助下，发现DNA在空白中呈短链分散，在单一抗生素的应力作用下伸长或卷曲，然后被压实，在联合应力下被压实，然后被碎片化，这可能是ARGs丰度随应力变化的原因。ROX和OTC增加了与疾病相关的厚壁菌门/拟杆菌门的比例。intI2和intI3与tetS之间非常显著的相关性（p≤0.001）暗示了ARG在肠道中传播的高风险。总之，我们的研究结果表明，在暴露于环境浓度的抗生素后，肠道ARG的相对丰度可能会根据肠道微生物组和DNA结构而改变。
Abstract
The intestinal flora is one of the most important environments for antibiotic resistance development, owing to its diverse mix of bacteria. An excellent medicine model organism, Xenopus tropicalis, was selected to investigate the spread of antibiotic resistance genes (ARGs) in the intestinal bacterial community with single or combined exposure to roxithromycin (ROX) and oxytetracycline (OTC). Seventeen resistance genes (tetA, tetB, tetE, tetM, tetO, tetS, tetX, ermF, msrA, mefA, ereA, ereB, mphA, mphB, intI1, intI2, intI3) were detected in the intestines of Xenopus tropicalis living in three testing tanks (ROX tanks, OTC tanks, ROX + OTC tanks) and a blank tank for 20 days. The results showed that the relative abundance of total ARGs increased obviously in the tank with single stress but decreased in the tank with combined stress, and the genes encoding the macrolide antibiotic efflux pump (msrA), phosphatase (mphB) and integron (intI2, intI3) were the most sensitive. With the aid of AFM scanning, DNA was found to be scattered short chain in the blank, became extended or curled and then compacted with the stress from a single antibiotic, and was compacted and then fragmented with combined stress, which might be the reason for the variation of the abundance of ARGs with stress. The ratio of Firmicutes/Bacteroides related to diseases was increased by ROX and OTC. The very significant correlation between intI2 and intI3 with tetS (p ≤ 0.001) hinted at a high risk of ARG transmission in the intestines. Collectively, our results suggested that the relative abundance of intestinal ARGs could be changed depending on the intestinal microbiome and DNA structures upon exposure to antibiotics at environmental concentrations.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722002662