Contribution of Novel Amino Acid Alterations in PmrA or PmrB to Colistin Resistance in mcr-Negative Escherichia coli Clinical Isolates, Including Major Multidrug-Resistant Lineages O25b:H4-ST131-H30Rx and Non-x
Contribution of Novel Amino Acid Alterations in PmrA or PmrB to Colistin Resistance in mcr-Negative Escherichia coli Clinical Isolates, Including Major Multidrug-Resistant Lineages O25b:H4-ST131-H30Rx and Non-x
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DOI：
10.1128/aac.00864-18
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发表时间：
2018-09-01
影响因子：
4.9
通讯作者：
Yokota, Shin-ichi
中科院分区：
文献类型：
--
作者：
Sato, Toyotaka;Shiraishi, Tsukasa;Yokota, Shin-ichi
粘菌素是多重耐药革兰氏阴性菌的最后一线药物。我们先前报告了4株质粒介导的粘菌素耐药（mcr）基因阴性的粘菌素耐药大肠埃希菌临床分离株，包括主要致病性和氟喹诺酮耐药菌株O25 b：H4-ST 131-H30 Rx（分离株SRE 34和SRE 44;粘菌素的MIC = 16 mg/L）、non-x（SME 296; MIC = 8 mg/L）和O 18-ST 416（SME 222; MIC = 4 mg/L）。在这项研究中，我们研究了粘菌素耐药机制，并确定了新的氨基酸取代或删除的PmrAB双组分系统，激活eptA（编码磷酸乙醇胺转移酶）和arnT（编码十一异戊二烯磷酸-α-4-氨基-4-脱氧-L-阿拉伯糖阿拉伯糖转移酶）在所有粘菌素耐药菌株。SRE 34在PmrB中具有缺失Delta 27-45（LISVFWLWHEST EQIQLFE），SRE 44在PmrA中具有取代L105 P，并且SME 222和SME 296在PmrB中均包括取代G206 D。基质辅助激光解吸电离-飞行时间质谱显示，脂质A修饰磷酸乙醇胺在所有四个菌株。pmrAB的缺失将粘菌素MIC降低至0.5 mg/L，并降低了eptA和arnT的表达。在粘菌素敏感的O25 b：H4-ST 131菌株SME 98（粘菌素MIC = 0.5 mg/L）中突变的pmrA或pmrB的染色体置换使粘菌素MIC增加至相应亲本粘菌素抗性分离株的MIC。此外，其中pmrAB被替换为突变的pmrAB的SME 98突变体在细菌生长和竞争培养方面与亲本菌株没有显着差异，除了在PmrA中具有L105 P的突变体，其生长在亲本菌株的存在下被显着抑制。总之，一些O25 b：H4-ST 131菌株似乎通过PmrAB中的氨基酸变化经由脂质A的磷酸乙醇胺修饰获得粘菌素抗性，并且PmrB中的氨基酸变化不影响细菌生长。
Colistin is a last-line drug for multidrug-resistant Gram-negative bacteria. We previously reported four plasmid-mediated colistin resistance (mcr) gene-negative colistin-resistant Escherichia coli clinical isolates, including the major pathogenic and fluoroquinolone-resistant strains O25b:H4-ST131-H30Rx (isolates SRE34 and SRE44; MIC for colistin = 16 mg/liter), non-x (SME296; MIC = 8 mg/liter), and O18-ST416 (SME222; MIC = 4 mg/liter). In this study, we investigated the colistin resistance mechanism and identified novel amino acid substitutions or deletions in the PmrAB two-component system that activates eptA (encoding a phosphoethanolamine transferase) and arnT (encoding an undecaprenyl phosphate-alpha-4-amino-4-deoxy-L-arabinose arabinosyl transferase) in all colistin-resistant isolates. SRE34 possessed deletion Delta 27-45 (LISVFWLWHEST EQIQLFE) in PmrB, SRE44 possessed substitution L105P in PmrA, and both SME222 and SME296 included substitution G206D in PmrB. Matrix-assisted laser desorption ionization-time of flight mass spectrometry revealed that lipid A is modified with phosphoethanolamine in all four isolates. Deletion of pmrAB decreased colistin MICs to 0.5 mg/liter and lowered eptA and arnT expression. Chromosomal replacement of mutated pmrA or pmrB in colistin-susceptible O25b:H4-ST131 strain SME98 (colistin MIC = 0.5 mg/liter) increased the colistin MIC to that of the respective parent colistin-resistant isolate. In addition, SME98 mutants in which pmrAB was replaced with mutated pmrAB showed no significant differences in bacterial growth and competition culture from the parent strain, except for the mutant with L105P in PmrA, whose growth was significantly suppressed in the presence of the parent strain. In conclusion, some O25b:H4-ST131 strains appear to acquire colistin resistance via phosphoethanolamine modification of lipid A through amino acid changes in PmrAB, and the amino acid changes in PmrB do not influence bacterial growth.