J Environ Qual. 2013 Jan-Feb;42(1):173-8. doi: 10.2134/jeq2012.0162.
The World Health Organization has identified antibiotic resistance as one of the top three threats to global health. There is concern that the use of antibiotics as growth promoting agents in livestock production contributes to the increasingly problematic development of antibiotic resistance. Many antibiotics are excreted at high rates, and the land application of animal manures represents a significant source of environmental exposure to these agents. To evaluate the long-term effects of antibiotic exposure on soil microbial populations, a series of field plots were established in 1999 that have since received annual applications of a mixture of sulfamethazine (SMZ), tylosin (TYL), and chlortetracycline (CTC). During the first 6 yr (1999-2004) soils were treated at concentrations of 0, 0.01 0.1, and 1.0 mg kg soil, in subsequent years at concentrations of 0, 0.1, 1.0, and 10 mg kg soil. The lower end of this concentration range is within that which would result from an annual application of manure from medicated swine. Following ten annual applications, the fate of the drugs in the soil was evaluated. Residues of SMZ and TYL, but not CTC were removed much more rapidly in soil with a history of exposure to 10 mg/kg drugs than in untreated control soil. Residues of C-SMZ were rapidly and thoroughly mineralized to CO in the historically treated soils, but not in the untreated soil. A SMZ-degrading sp. was isolated from the treated soil. Overall, these results indicate that soil bacteria adapt to long-term exposure to some veterinary antibiotics resulting in sharply reduced persistence. Accelerated biodegradation of antibiotics in matrices exposed to agricultural, wastewater, or pharmaceutical manufacturing effluents would attenuate environmental exposure to antibiotics, and merits investigation in the context of assessing potential risks of antibiotic resistance development in environmental matrices.
世界卫生组织已将抗生素耐药性列为对全球健康的三大威胁之一。人们担心，在畜牧业生产中使用抗生素作为生长促进剂会导致抗生素耐药性日益严重的问题。许多抗生素被大量排泄，而动物粪便的土地应用是这些抗生素在环境中暴露的一个重要来源。为了评估抗生素暴露对土壤微生物种群的长期影响，1999 年建立了一系列田间试验小区，此后每年都施用磺胺甲恶唑（SMZ）、泰乐菌素（TYL）和金霉素（CTC）混合物。在最初的 6 年（1999-2004 年）中，土壤的处理浓度分别为 0、0.01、0.1 和 1.0mg/kg 土壤，随后几年的浓度分别为 0、0.1、1.0 和 10mg/kg 土壤。该浓度范围的低端处于每年应用含药猪粪的结果范围内。在进行了十次年度施药后，评估了土壤中药物的命运。在暴露于 10mg/kg 药物的土壤中，SMZ 和 TYL 的残留量比未处理对照土壤中更快地被去除，但 CTC 的残留量则不然。在历史上接受过处理的土壤中，C-SMZ 迅速而彻底地矿化为 CO，但在未处理的土壤中则不然。从处理过的土壤中分离出了一种能够降解 SMZ 的细菌。总的来说，这些结果表明，土壤细菌适应于长期暴露于某些兽医抗生素，从而导致抗生素的持久性大大降低。在暴露于农业、废水或制药生产废水的基质中，抗生素的加速生物降解将减轻环境中对抗生素的暴露，这值得在评估环境基质中抗生素耐药性发展的潜在风险的背景下进行研究。
