Pseudomonas aeruginosa reveals high intrinsic resistance to penem antibiotics:: Penem resistance mechanisms and their interplay
Pseudomonas aeruginosa reveals high intrinsic resistance to penem antibiotics:: Penem resistance mechanisms and their interplay
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DOI：
10.1128/aac.45.7.1964-1971.2001
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发表时间：
2001-07-01
影响因子：
4.9
通讯作者：
Nishino, T
中科院分区：
文献类型：
--
作者：
Okamoto, K;Gotoh, N;Nishino, T
铜绿假单胞菌对法罗培南、利提培南、AMA3176、苏洛培南、Sch29482和Sch34343等培南类抗生素具有较高的内在耐药性。为了研究培南耐药的机制，我们利用实验室菌株PAO1构建了一系列多药外排系统MexAB-OprM和/或染色体AmpC β -内酰胺酶受损的等基因突变体。通过诱导大肠杆菌主孔蛋白OmpF的表达，部分消除了PAO1的外膜屏障。利用突变体和OmpF表达质粒进行的药敏试验表明，MexAB-OprM和外膜屏障，而不是AmpC β -内酰胺酶，是PAO1高内在素耐药的主要机制。然而，将PAO1的高内禀培南耐药降低到与大肠杆菌等对培南敏感的革兰氏阴性菌相同的水平，需要同时丢失MexAB-OprM和AmpC β -内酰胺酶，或者同时丢失MexAB-OprM和外膜屏障。对青霉素结合蛋白（PBPs）的竞争实验表明，PBP 1b和PBP 2对法罗培南的亲和力分别比对亚胺培南的亲和力低1.8和1.5倍。与AmpC缺失的PAO1突变体相比，缺乏外膜屏障、MexAB和AmpC β -内酰胺酶增加了PAO1对亚胺培南的敏感性，因此，我们认为铜绿假单胞菌的高内源性培南耐药性是由外膜屏障、主动外排系统和AmpC β -内酰胺酶相互作用产生的，而不是由于PBPs对培南的亲和力较低。
Pseudomonas aeruginosa exhibits high intrinsic resistance to penem antibiotics such as faropenem, ritipenem, AMA3176, sulopenem, Sch29482, and Sch34343. To investigate the mechanisms contributing to penem resistance, we used the laboratory strain PAO1 to construct a series of isogenic mutants with an impaired multidrug efflux system MexAB-OprM and/or impaired chromosomal AmpC beta -lactamase. The outer membrane barrier of PAO1 was partially eliminated by inducing the expression of the plasmid encoded Escherichia coli major porin OmpF. Susceptibility tests using the mutants and the OmpF expression plasmid showed that MexAB-OprM and the outer membrane barrier, but not AmpC beta -lactamase, are the main mechanisms involved in the high intrinsic penem resistance of PAO1. However, reducing the high intrinsic penem resistance of PAO1 to the same level as that of penem-susceptible gram-negative bacteria such as E. coli required the loss of either both MexAB-OprM and AmpC beta -lactamase or both MexAB-OprM and the outer membrane barrier. Competition experiments for penicillin-binding proteins (PBPs) revealed that the affinity of PBP 1b and PBP 2 for faropenem were about 1.8- and 1.5-fold lower, than the respective affinity for imipenem. Loss of the outer membrane barrier, MexAB, and AmpC beta -lactamase increased the susceptibility of PAO1 to almost all penems tested compared to the susceptibility of the AmpC-deficient PAO1 mutants to imipenem, Thus, it is suggested that the high intrinsic penem resistance of P. aeruginosa is generated from the interplay among the outer membrane barrier, the active efflux system, and AmpC beta -lactamase but not from the lower affinity of PBPs for penems.