贫营养和痕量抗生素对质粒抗生素抗性适应度代价的影响

本文针对饮用水系统中营养和抗生素水平对质粒抗生素抗性的适应度代价进行了研究.选取了p ACYC184、RP4和PBR322这3种不同的抗性质粒,发现在不同的营养水平下,抗性质粒的适应度代价具有普遍性.而且,营养水平越低,其适应度代价表现得越明显.另外,痕量浓度的抗生素也会影响抗性质粒的适应度代价.本研究中,小于50%MIC的抗生素浓度对野生菌的损伤或抑制作用不足以抗衡抗性质粒的适应度代价,质粒难以维持.因而,推断在饮用水系统(贫营养和ng·L-1水平的抗生素)中,质粒抗生素抗性的适应度代价较大,质粒不易维持,在饮用水系统中传播和扩散的风险较小.

Effects of Low-level Nutrition and Trace Antibiotics on the Fitness Cost of Plasmids Bearing Antibiotic Resistance

The effects of nutrition and antibiotic level on fitness costs of plasmid containing antibiotic resistance in drinking water system were investigated in this study. Three plasmids harboring different antibiotic resistances, i.e. pACYC184, RP4, and PBR322, were selected. It was found that the antibiotic resistance imposed cost on the fitness of all plasmids at different nutrition levels, which was universal. Moreover, the fitness costs were larger at lower nutrition levels. Besides, the fitness costs of plasmid bearing antibiotic resistance were also affected by trace antibiotics. In this study, when exposed to antibiotics (lower than 50% MIC), the fitness costs of plasmid imposed to the bacteria were more apparent than the injury or inhibition effect by antibiotics. The plasmids were unstable. Therefore, it was inferred that the plasmid containing antibiotic resistance imposed large fitness costs on bacteria in drinking water system (with low-level nutrition and ng·L^-1 level antibiotic), and it was not stable. Thus, the risk of plasmid bearing antibiotic resistance transmission and spread in drinking water system was low.