Sequence Duplication Within pmrB Gene Contribute to High-Level Colistin Resistance in Avian Pathogenic Escherichia coli
Sequence Duplication Within pmrB Gene Contribute to High-Level Colistin Resistance in Avian Pathogenic Escherichia coli
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pmrB 基因内的序列重复导致禽致病性大肠杆菌的高水平粘菌素耐药性
DOI：
10.1089/mdr.2019.0290
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发表时间：
2019-11-26
影响因子：
2.6
通讯作者：
Wang, Liping
中科院分区：
文献类型：
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作者：
Huang, Jinhu;Dai, Xingyang;Wang, Liping
除了质粒编码机制的出现之外，pmrAB基因的突变仍然是大肠杆菌中主要的粘菌素耐药机制之一。然而，高水平粘菌素耐药（HLCR）的机制尚未阐明。在这项研究中，我们评估了5株对粘菌素敏感的禽致病性大肠杆菌（APEC）暴露于粘菌素后的HLCR机制。检测到3个PmrB突变（G19R、L167P、V88E）和2个PmrB序列重复（PmrB-sd）突变（68-77dup和94-156dup）。染色体替换和缺失突变表明，这两种PmrB-sd突变有助于APEC菌株的HLCR，但不是完全负责。定量逆转录/聚合酶链反应（qRT-PCR）显示PmrB-sd诱导突变体pmrAB转录水平升高，而PmrB-sd逆转突变体pmrAB表达降低。所有五种诱导突变体对氟苯尼考和四环素的最低抑制浓度均降低。此外，4个突变体（G19R、L167P、V88E和94-156dup）和2个突变体（68-77dup和94-156dup）对头孢替福和庆大霉素的敏感性也分别增加。诱导突变体的Zeta电位测定结果表明，在不含粘菌素的情况下，细胞表面的负电荷比亲本菌株少。诱导突变体的滞后时间增加，适应度降低。总之，鉴定导致HLCR的新型PmrB-sd突变有助于拓宽对粘菌素耐药的认识。应注意使用粘菌素治疗由APEC菌株引起的感染。
Beyond the emergence of plasmid-encoded mechanisms, mutation within the pmrAB genes remains one of the primary colistin resistance mechanisms in Escherichia coli. However, the mechanisms of high-level colistin resistance (HLCR) have not been elucidated. In this study, we evaluated the HLCR mechanisms in five colistin-susceptible Avian pathogenic Escherichia coli (APEC) isolates after colistin exposure. Three PmrB substitutions (G19R, L167P, V88E) and two PmrB sequence duplication (PmrB-sd) mutations (68-77dup and 94-156dup) were detected. Chromosomal replacement and deletion mutagenesis revealed the two PmrB-sd mutations contribute to, but are not fully responsible for, HLCR in APEC strains. Quantitative reverse transcription/polymerase chain reaction (qRT-PCR) revealed that the PmrB-sd induction mutants showed an increased pmrAB transcript level and the PmrB-sd reversion mutants exhibited a reduction of pmrAB expression. All five induction mutants exhibited decreased minimum inhibitory concentrations to florfenicol and tetracycline. In addition, four mutants (G19R, L167P, V88E, and 94-156dup) and two mutants (68-77dup and 94-156dup) also displayed increased sensitivity to ceftiofur and gentamicin, respectively. Zeta potential measurement of the induction mutants showed that there was less negative charge on the cell surface compared with its parental strains in the absence of colistin. The induction mutants also showed an increase of lag time and decrease of fitness. In summary, the identification of novel PmrB-sd mutations contributing to HLCR is helpful to broaden the knowledge of colistin resistance. Attention should be paid to the use of colistin for the treatment of infections caused by APEC strains.