Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany.
Appl Environ Microbiol. 2013 Mar;79(5):1704-11. doi: 10.1128/AEM.03172-12. Epub 2013 Jan 11.
Spreading manure containing antibiotics in agriculture is assumed to stimulate the dissemination of antibiotic resistance in soil bacterial populations. Plant roots influencing the soil environment and its microflora by exudation of growth substrates might considerably increase this effect. In this study, the effects of manure from pigs treated with sulfadiazine (SDZ), here called SDZ manure, on the abundance and transferability of sulfonamide resistance genes sul1 and sul2 in the rhizosphere of maize and grass were compared to the effects in bulk soil in a field experiment. In plots that repeatedly received SDZ manure, a significantly higher abundance of both sul genes was detected compared to that in plots where manure from untreated pigs was applied. Significantly lower abundances of sul genes relative to bacterial ribosomal genes were encountered in the rhizosphere than in bulk soil. However, in contrast to results for bulk soil, the sul gene abundance in the SDZ manure-treated rhizosphere constantly deviated from control treatments over a period of 6 weeks after manuring, suggesting ongoing antibiotic selection over this period. Transferability of sulfonamide resistance was analyzed by capturing resistance plasmids from soil communities into Escherichia coli. Increased rates of plasmid capture were observed in samples from SDZ manure-treated bulk soil and the rhizosphere of maize and grass. More than 97% of the captured plasmids belonged to the LowGC type (having low G+C content), giving further evidence for their important contribution to the environmental spread of antibiotic resistance. In conclusion, differences between bulk soil and rhizosphere need to be considered when assessing the risks associated with the spreading of antibiotic resistance.
在农业中散布含有抗生素的粪便被认为会刺激土壤细菌种群中抗生素耐药性的传播。植物根系通过分泌生长基质来影响土壤环境及其微生物群落，这可能会极大地增加这种影响。在这项研究中，我们将磺胺嘧啶（SDZ）处理过的猪粪（称为 SDZ 粪肥）对玉米和草根际中磺胺类耐药基因 sul1 和 sul2 的丰度和可转移性的影响与田间试验中 bulk soil 的影响进行了比较。在重复施 SDZ 粪肥的地块中，与施未处理猪粪的地块相比，发现两个 sul 基因的丰度显著增加。与 bulk soil 相比，根际中 sul 基因的丰度相对于细菌核糖体基因显著降低。然而，与 bulk soil 的结果相反，在施肥后 6 周内，SDZ 粪肥处理的根际中 sul 基因的丰度持续偏离对照处理，表明在此期间持续存在抗生素选择。通过从土壤群落中捕获抗性质粒到大肠杆菌中，分析了磺胺类耐药性的可转移性。在施 SDZ 粪肥的 bulk soil 和玉米、草根际的样品中，观察到质粒捕获率增加。捕获的质粒中超过 97%属于低 GC 型（GC 含量低），这进一步证明了它们对环境中抗生素耐药性传播的重要贡献。总之，在评估与抗生素耐药性传播相关的风险时，需要考虑 bulk soil 和根际之间的差异。
