Department of Biology, Point Loma Nazarene University, San Diego, California 92106, USA.
Environ Sci Technol. 2011 Jan 15;45(2):447-54. doi: 10.1021/es1029206. Epub 2010 Dec 8.
Contamination of soil and water with antibiotic-resistant bacteria may create reservoirs of antibiotic resistance genes that have the potential to negatively impact future public health through horizontal gene transfer. The plasmid-mediated quinolone resistance genes qnrA, qnrB, qnrS, qepA, and aac(6')-Ib-cr were detected by PCR amplification of metagenomic DNA from surface sediments of the Tijuana River Estuary, a sewage-impacted coastal wetland along the U.S.-Mexico border; sediments of Famosa Slough, a nearby urban wetland that is largely unaffected by sewage, contained only qnrB, qnrS, and qepA. The number of PCR-positive sites and replicates increased in both wetlands after rainfall. Real-time quantitative PCR revealed a significant increase (p < 0.0005) in qnrA abundance (copies per gram sediment or per 16S rDNA copy) in Tijuana River Estuary sediments immediately following rainfall, but no significant change was measured at Famosa Slough (p > 0.1). Nucleotide sequences of cloned qnrA amplicons were all affiliated with qnrA genes found on plasmids of clinical isolates with one exception that was most similar to the chromosomal qnrA gene found in Shewanella algae. Our results suggest that urban wetlands may become reservoirs of antibiotic resistance genes, particularly where wastewater is improperly managed.
土壤和水中的抗生素耐药菌的污染可能会产生抗生素耐药基因库，这些基因库有可能通过水平基因转移对未来的公共健康产生负面影响。本研究采用聚合酶链反应（PCR）扩增法，从美墨边境受污水影响的沿海湿地——蒂华纳河口的表层沉积物中检测到了质粒介导的喹诺酮耐药基因 qnrA、qnrB、qnrS、qepA 和 aac(6')-Ib-cr；而在附近基本不受污水影响的城市湿地——法莫萨泻湖的沉积物中，仅检测到了 qnrB、qnrS 和 qepA。雨后，两个湿地中的 PCR 阳性位点和重复次数均有所增加。实时定量 PCR 显示，雨后蒂华纳河口沉积物中 qnrA 的丰度（每克沉积物或每 16S rDNA 拷贝的拷贝数）显著增加（p < 0.0005），而法莫萨泻湖则没有显著变化（p > 0.1）。克隆 qnrA 扩增子的核苷酸序列均与临床分离株质粒上的 qnrA 基因有关，只有一个例外，与在 Shewanella algae 中发现的染色体 qnrA 基因最为相似。我们的研究结果表明，城市湿地可能成为抗生素耐药基因的库，特别是在废水处理不当的情况下。
