Induction of Efflux-Mediated Macrolide Resistance in Streptococcus pneumoniae
Induction of Efflux-Mediated Macrolide Resistance in Streptococcus pneumoniae
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DOI：
10.1128/aac.00060-11
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发表时间：
2011-07-01
影响因子：
4.9
通讯作者：
Stephens, David S.
中科院分区：
文献类型：
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作者：
Chancey, Scott T.;Zhou, Xiaoliu;Stephens, David S.
肺炎链球菌和其它革兰氏阳性菌中由移动的遗传元件MEGA上的操纵子mef（E）-mel编码的抗菌外排系统可被大环内酯类抗生素和抗菌肽诱导。诱导可能会影响大环内酯类药物的临床反应。我们开发了mef（E）报告基因构建体和纸片扩散诱导和抗性测定以确定mef（E）-mel诱导的动力学和基础。诱导发生迅速，在暴露于亚抑制浓度的红霉素的1小时内转录增加>15倍。一系列环境条件，包括感受态和具有不同细胞靶点的非大环内酯类抗生素，均未诱导mef（E）。使用16种不同结构的大环内酯，诱导与连接到大环内酯内酯环C-5的氨基糖相关，而不是与大小相关（e.例如，在一个实施例中，14-、15-或16-元）或在C-3处存在中性糖克拉定糖。已知具有连接到C-5的单糖的大环内酯类在掺入多达八个氨基酸后可以阻止新生肽从核糖体中退出，从而诱导mef（E）表达。含有C-5二糖的大环内酯类药物（可将大环内酯类药物延伸至核糖体出口通道，破坏肽基转移酶活性）不会诱导mef（E）的产生，但大环内酯类药物对核糖体的亲和力决定了mef（E）的产生和肺炎球菌的易感性。通过诱导大环内酯类诱导mef（E）-mel表达似乎是基于大环内酯C-5糖与核糖体的特异性相互作用，其减轻mef（E）-mel的转录衰减。
The antimicrobial efflux system encoded by the operon mef(E)-mel on the mobile genetic element MEGA in Streptococcus pneumoniae and other Gram-positive bacteria is inducible by macrolide antibiotics and antimicrobial peptides. Induction may affect the clinical response to the use of macrolides. We developed mef(E) reporter constructs and a disk diffusion induction and resistance assay to determine the kinetics and basis of mef(E)-mel induction. Induction occurred rapidly, with a >15-fold increase in transcription within 1 h of exposure to subinhibitory concentrations of erythromycin. A spectrum of environmental conditions, including competence and nonmacrolide antibiotics with distinct cellular targets, did not induce mef(E). Using 16 different structurally defined macrolides, induction was correlated with the amino sugar attached to C-5 of the macrolide lactone ring, not with the size (e. g., 14-, 15- or 16-member) of the ring or with the presence of the neutral sugar cladinose at C-3. Macrolides with a monosaccharide attached to C-5, known to block exit of the nascent peptide from the ribosome after the incorporation of up to eight amino acids, induced mef(E) expression. Macrolides with a C-5 disaccharide, which extends the macrolide into the ribosomal exit tunnel, disrupting peptidyl transferase activity, did not induce it. The induction of mef(E) did not require macrolide efflux, but the affinity of macrolides for the ribosome determined the availability for efflux and pneumococcal susceptibility. The induction of mef(E)-mel expression by inducing macrolides appears to be based on specific interactions of the macrolide C-5 saccharide with the ribosome that alleviate transcriptional attenuation of mef(E)-mel.