PNAS一项研究提出，中国动物养殖厂不加监管地使用抗生素可能促进多种耐抗生素基因的大量出现并释放到环境中去。中国是全世界最大的抗生素制造者和消费者；然而，在中国使用抗生素治疗牲畜疾病和促进动物生长的做法并没有得到监管。Yong-Guan Zhu、James M. Tiedje及其同事确定了中国的3个大型商业养猪场的动物粪便、堆肥和土壤中的超过100种抗生素耐药基因的不同类型和浓度。这组作者报告说，每个养殖场的动物粪便都含有能够带来对所有主要类型的抗生素耐药的基因，这也涉及到那些没有在这个具体地点使用过的药物。该研究确定了149个独特的抗生素耐药性基因——其中一些的表达水平是对照样本的192到2.8万倍。另外，这些发现还提示抗生素和砷、铜等金属同时存在可能会增加抗生素耐药性的自然选择。这组作者说，含有抗生素耐药细菌的动物粪便、堆肥或土壤如果流入河流、渗透到地下水中、以灰尘的形式分散或者堆肥以有机肥料的形式分销，这些都可能妨碍到人类抗生素疗法的有效性。
doi:10.1073/pnas.1222743110
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Diverse and abundant antibiotic resistance genes in Chinese swine farms
Yong-Guan Zhua,b,1,2, Timothy A. Johnsonc,d,1, Jian-Qiang Sua, Min Qiaob, Guang-Xia Guob, Robert D. Stedtfeldc,e, Syed A. Hashshamc,e, and James M. Tiedjec,d,2
Antibiotic resistance genes (ARGs) are emerging contaminants posing a potential worldwide human health risk. Intensive animal husbandry is believed to be a major contributor to the increased environmental burden of ARGs. Despite the volume of antibiotics used in China, little information is available regarding the corresponding ARGs associated with animal farms. We assessed type and concentrations of ARGs at three stages of manure processing to land disposal at three large-scale (10,000 animals per year) commercial swine farms in China. In-feed or therapeutic antibiotics used on these farms include all major classes of antibiotics except vancomycins. High-capacity quantitative PCR arrays detected 149 unique resistance genes among all of the farm samples, the top 63 ARGs being enriched 192-fold (median) up to 28,000-fold (maximum) compared with their respective antibiotic-free manure or soil controls. Antibiotics and heavy metals used as feed supplements were elevated in the manures, suggesting the potential for coselection of resistance traits. The potential for horizontal transfer of ARGs because of transposon-specific ARGs is implicated by the enrichment of transposases—the top six alleles being enriched 189-fold (median) up to 90,000-fold in manure—as well as the high correlation (r2 = 0.96) between ARG and transposase abundance. In addition, abundance of ARGs correlated directly with antibiotic and metal concentrations, indicating their importance in selection of resistance genes. Diverse, abundant, and potentially mobile ARGs in farm samples suggest that unmonitored use of antibiotics and metals is causing the emergence and release of ARGs to the environment.
