摘要

了解抗生素耐药基因( ARGs)的起源和传播对于了解现代环境中的耐药基因至关重要。通过对ARGs在相对原始和人为影响环境中的宏基因组图谱的比较研究，可以揭示ARGs的传播机制。南海深海海底（SCS）被认为基本上没有人为影响，而中国南方的珠江口( PRE)受到了密集人类活动的严重影响。通过化学分析SCS和PRE沉积物，发现PRE沉积物中检出常用抗生素(磺胺甲基嗪、诺氟沙星、氧氟沙星、四环素、红霉素)，但在SCS沉积物中未检出。在相对原始的SCS沉积物中，最普遍和最丰富的ARGs是大环内酯类和多肽抗性相关的ARGs，其主要机制是外排泵。在受污染的沉积物中，典型的ARG谱表明，对人类健康和动物养殖中常用的抗生素(包括磺胺类、氟喹诺酮类和氨基糖苷类)具有普遍的耐药性，基因型和耐药机制的多样性均高于SCS。特别是，抗生素灭活显著地促进了PRE沉积物中氨基糖苷类、β-内酰胺类和大环内酯类的抗性。ARGs是水环境中传播载体，其的丰度水平与可移动遗传元件(包括整合子和质粒)的丰度水平密切相关。当前研究的宏基因组结果支持这样一种观点，即ARGs自然起源于原始环境，而人类活动加速ARGs的传播，从而使微生物能够耐受选择性环境压力以应对人为影响。

Knowledge of the origins and dissemination of antibiotic resistance genes (ARGs) is essential for understanding modern resistomes in the environment. The mechanisms of the dissemination of ARGs can be revealed through comparative studies on the metagenomic profiling of ARGs between relatively pristine and human-impacted environments. The deep ocean bed of the South China Sea (SCS) is considered to be largely devoid of anthropogenic impacts, while the Pearl River Estuary (PRE) in south China has been highly impacted by intensive human activities. Commonly used antibiotics (sulfamethazine, norfloxacin, ofloxacin, tetracycline, and erythromycin) have been detected through chemical analysis in the PRE sediments, but not in the SCS sediments. In the relatively pristine SCS sediments, the most prevalent and abundant ARGs are those related to resistance to macrolides and polypeptides, with efflux pumps as the predominant mechanism. In the contaminated PRE sediments, the typical ARG profiles suggest a prevailing resistance to antibiotics commonly used in human health and animal farming (including sulfonamides, fluoroquinolones, and aminoglycosides), and higher diversity in both genotype and resistance mechanism than those in the SCS. In particular, antibiotic inactivation significantly contributed to the resistance to aminoglycosides, 尾-lactams, and macrolides observed in the PRE sediments. There was a significant correlation in the levels of abundance of ARGs and those of mobile genetic elements (including integrons and plasmids), which serve as carriers in the dissemination of ARGs in the aquatic environment. The metagenomic results from the current study support the view that ARGs naturally originate in pristine environments, while human activities accelerate the dissemination of ARGs so that microbes would be able to tolerate selective environmental stress in response to anthropogenic impacts.

http://pubs.acs.org/doi/abs/10.1021/es403818e