Substitutions in PBP3 confer resistance to both ampicillin and extended‐spectrum cephalosporins in Haemophilus parainfluenzae as revealed by site‐directed mutagenesis and gene recombinants
Substitutions in PBP3 confer resistance to both ampicillin and extended‐spectrum cephalosporins in Haemophilus parainfluenzae as revealed by site‐directed mutagenesis and gene recombinants
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定点诱变和基因重组显示，PBP3 的取代导致副流感嗜血杆菌对氨苄西林和广谱头孢菌素产生耐药性
DOI：
10.1093/jac/dkx157
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发表时间：
2017
影响因子：
5.2
通讯作者：
N. Nørskov
中科院分区：
文献类型：
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作者：
Nanna H Wienholtz;Aynur Barut;N. Nørskov
目的：探讨副流感嗜血杆菌PBP3基因氨基酸替换与-BGR；-内酰胺类药物敏感性的关系。方法：采用定点突变的方法，将385、511和526位氨基酸的单一和多个突变引入副流感嗜血杆菌敏感株PBP3。从编码多个氨基酸替换的临床菌株中也用聚合酶链式反应扩增FTSI产生重组子。用ETEST®测定氨苄西林、头孢呋辛、头孢噻肟和头孢曲松的最低抑菌浓度。结果：用编码PBP3转肽酶区域4个替换的临床分离株的FTSI转化敏感株，可使其对氨苄西林耐药，但对头孢菌素类不耐药。从一株编码8个替换的临床菌株中引入FTSI，使其对氨苄西林、头孢噻肟和头孢曲松产生耐药性。重组子的最低抑菌浓度低于供体菌株。使用定点突变，虽然V511A将头孢呋辛的MIC增加到静脉给药的中间类别，但没有一个单一的替代导致对被测试的&BGR；-内酰胺类抗生素产生耐药性。编码N526K/H/S和V511A的重组子对氨苄西林耐药。如果同时存在V511A，则S385T替代增加了第三代头孢菌素的MIC值。结论：副流感嗜血杆菌PBP3基因的替换足以使其对氨苄西林和第三代头孢菌素产生耐药性。Val-511和Asn-526位置的替换组合使其对氨苄西林产生耐药性。对第三代头孢菌素的耐药性可能需要PBP3中四个以上的替换。
Objectives: To determine the association of amino acid substitutions in PBP3 with &bgr;‐lactam susceptibility in Haemophilus parainfluenzae. Methods: Single and multiple amino acid mutations at positions 385, 511 and 526 were introduced into PBP3 of a &bgr;‐lactam‐susceptible H. parainfluenzae strain using site‐directed mutagenesis. Recombinants were also generated using PCR‐amplified ftsI from clinical strains encoding multiple amino acid substitutions. MICs of ampicillin, cefuroxime, cefotaxime and ceftriaxone were determined using Etest®. Results: Transformation of a susceptible strain with ftsI from clinical strains encoding four substitutions in the transpeptidase region of PBP3 conferred resistance to ampicillin, but not to cephalosporins. Introduction of ftsI from a clinical strain encoding eight substitutions conferred resistance to ampicillin, cefotaxime and ceftriaxone. MICs for recombinants were lower than those for the donor strains. Using site‐directed mutagenesis, no single substitution conferred resistance to the tested &bgr;‐lactams, although V511A increased the MIC of cefuroxime to the intermediate category for intravenous administration. Recombinants encoding N526K/H/S in combination with V511A were resistant to ampicillin. Substitution S385T increased the MICs of third‐generation cephalosporins if V511A was also present. Conclusions: Substitutions in PBP3 are sufficient to confer resistance to both ampicillin and third‐generation cephalosporins in H. parainfluenzae. A combination of substitutions at positions Val‐511 and Asn‐526 confers resistance to ampicillin. Resistance to third‐generation cephalosporins probably requires more than four substitutions in PBP3.