Knapp Charles W, Engemann Christina A, Hanson Mark L, Keen Patricia L, Hall Kenneth J, Graham David W
Department of Civil, Environmental and Architectural Engineering, University of Kansas, Lawrence, Kansas 66045, USA.
Environ Sci Technol. 2008 Jul 15;42(14):5348-53. doi: 10.1021/es703199g.
Subinhibitory levels of antibiotics can promote the development of antibiotic resistance in bacteria. However, it is unclear whether antibiotic concentrations released into aquatic systems exert adequate pressure to select populations with resistance traits. To examine this issue, 15 mesocosms containing pristine surface water were treated with oxytetracycline (OTC) for 56 days at five levels (0, 5, 20, 50, and 250 microg L(-1)), and six tetracycline-resistance genes (tet(B), tet(L), tet(M), ted(O), tet(Q), and tet(W)), the sum of those genes (tet(R)), "total" 16S-rRNA genes, and transposons (Tn916 and Tn 1545) were monitored using real-time PCR. Absolute water-column resistance-gene abundances did not change at any OTC exposure. However, an increase was observed in the ratio of tet(R) to 16S-rRNA genes in the 250 microg L(-1) OTC units, and an increase in the selection rate of Tc(r) genes (relative to 16S-rRNA genes) was seen when OTC levels were at 20 microg L(-1). Furthermore, tet(M) and Tn916/1545 gene abundances correlated among all treatments (r2 = 0.701, p = 0.05), and there were similar selection patterns of tetR and Tn916/1545 genes relative to the OTC level, suggesting a possible mechanism for retention of specific resistance genes within the systems.
抗生素的亚抑制水平可促进细菌耐药性的发展。然而，尚不清楚释放到水生系统中的抗生素浓度是否会对具有耐药性状的菌群施加足够的选择压力。为研究此问题，用土霉素（OTC）对15个装有原始地表水的中型生态系统进行了56天的处理，设置了五个浓度水平（0、5、20、50和250微克/升），并使用实时荧光定量PCR监测了六种四环素抗性基因（tet(B)、tet(L)、tet(M)、tet(O)、tet(Q)和tet(W)）、这些基因的总和（tet(R)）、“总”16S核糖体RNA基因以及转座子（Tn916和Tn1545）。在任何OTC暴露水平下，水柱中抗性基因的绝对丰度均未发生变化。然而，在250微克/升OTC处理组中，观察到tet(R)与16S核糖体RNA基因的比例有所增加，当OTC浓度为20微克/升时，Tc(r)基因（相对于16S核糖体RNA基因）的选择率有所增加。此外，在所有处理组中，tet(M)和Tn916/1545基因的丰度具有相关性（r2 = 0.701，p = 0.05），并且tetR和Tn916/1545基因相对于OTC水平具有相似的选择模式，这表明系统内特定抗性基因的保留可能存在一种机制。
