Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, Singapore 117576, Singapore.
Water Res. 2011 May;45(10):3098-106. doi: 10.1016/j.watres.2011.03.025. Epub 2011 Mar 21.
A variety of antibiotics and their metabolites at sub-inhibitory level concentrations are suspected to expand resistance genes in the environment. However, knowledge is limited on the causal correlation of trace antibiotics or their metabolites with resistance proliferation. In this study, erythromycin (ERY) resistance genes were screened on microbial consortia of sequencing batch reactors (SBRs) after one year acclimation to ERY (100 μg/L) or dehydrated erythromycin (ERY-H(2)O, 50 μg/L). The identified esterase gene ereA explains that ERY could be degraded to six products by microbes acclimated to ERY (100 μg/L). However, ERY could not be degraded by microbes acclimated to ERY-H(2)O (50 μg/L), which may be due to the less proliferated ereA gene. Biodegradation of ERY required the presence of exogenous carbon source (e.g., glucose) and nutrients (e.g., nitrogen, phosphorus) for assimilation, but overdosed ammonium-N (>40 mg/L) inhibited degradation of ERY. Zoogloea, a kind of biofilm formation bacteria, became predominant in the ERY degradation consortia, suggesting that the input of ERY could induce biofilm resistance to antibiotics. Our study highlights that lower μg/L level of ERY or ERY-H(2)O in the environment encourages expansion of resistance genes in microbes.
各种抗生素及其亚抑制浓度的代谢物被怀疑会在环境中扩大耐药基因。然而，关于痕量抗生素或其代谢物与耐药性增殖之间的因果关系的知识有限。在这项研究中，在经过一年的红霉素（ERY）（100μg/L）或脱水红霉素（ERY-H₂O，50μg/L）驯化后，在序批式反应器（SBR）微生物群落中筛选红霉素抗性基因。鉴定的酯酶基因 ereA 表明，微生物驯化后的 ERY（100μg/L）可将 ERY 降解为六种产物。然而，微生物驯化后的 ERY-H₂O（50μg/L）不能降解 ERY，这可能是因为 ereA 基因增殖较少。ERY 的生物降解需要外源性碳源（如葡萄糖）和同化所需的营养物质（如氮、磷），但过量的铵-N（>40mg/L）抑制了 ERY 的降解。动胶菌，一种生物膜形成细菌，在 ERY 降解菌群中占优势，表明 ERY 的投入会诱导抗生素的生物膜耐药性。我们的研究强调，环境中较低μg/L 水平的 ERY 或 ERY-H₂O 会鼓励微生物中耐药基因的扩张。
