Blodkamp Stefanie, Kadlec Kristina, Gutsmann Thomas, Quiblier Chantal, Naim Hassan Y, Schwarz Stefan, von Köckritz-Blickwede Maren
Department of Physiological Chemistry, University of Veterinary Medicine, Hannover, Germany; Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Neustadt-Mariensee, Germany.
Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, Neustadt-Mariensee, Germany.
Vet Microbiol. 2017 Feb;200:52-58. doi: 10.1016/j.vetmic.2016.03.021. Epub 2016 Mar 31.
Antimicrobial peptides (AMPs) represent an important part of the innate host immune system. Although they are active against a broad range of pathogens, bacteria have evolved different resistance mechanisms to avoid killing by AMPs. Since not much is known about the impact of efflux pumps on the susceptibility of Gram-positive bacteria to AMPs, especially to the cathelicidins, the aim of this study was to analyze whether Staphylococcus aureus can use efflux pumps to resist the antimicrobial effects of cathelicidins derived from different animal species (human, mouse, rabbit or cattle). For this purpose the minimal inhibitory concentrations (MICs) of S. aureus field isolates for the cathelicidins LL-37, mCRAMP, CAP18, BMAP-27 and BMAP-28 in the presence and absence of different efflux pump inhibitors were determined. Furthermore, the MICs of mutants lacking SecDF, a member of the RND efflux pump family, were determined and compared to the MICs of their respective wildtype and complemented strains. The data demonstrated that after blocking RND-type efflux pumps with 1-(1-naphthylmethyl)-piperazine, the MICs for CAP18, but not those for the other cathelicidins tested, were significantly decreased. In good correlation with these data, significantly decreased MICs for CAP18 and also BMAP-27 have been observed for SecDF knockout mutants as compared to their isogenic wildtype strains. In addition, the MIC values increased again after re-introducing a cloned secDF via plasmid complementation. These results indicated an involvement of SecDF in a reduced efficacy of species-specific cathelicidins against S. aureus.
抗菌肽（AMPs）是宿主固有免疫系统的重要组成部分。尽管它们对多种病原体具有活性，但细菌已进化出不同的耐药机制以避免被AMPs杀死。由于关于外排泵对革兰氏阳性菌对AMPs敏感性的影响，尤其是对cathelicidins的影响了解不多，本研究的目的是分析金黄色葡萄球菌是否可以利用外排泵来抵抗源自不同动物物种（人、小鼠、兔或牛）的cathelicidins的抗菌作用。为此，测定了在存在和不存在不同外排泵抑制剂的情况下，金黄色葡萄球菌临床分离株对cathelicidins LL-37、mCRAMP、CAP18、BMAP-27和BMAP-28的最低抑菌浓度（MICs）。此外，还测定了缺乏RND外排泵家族成员SecDF的突变体的MICs，并将其与各自野生型和互补菌株的MICs进行比较。数据表明，用1-(1-萘甲基)-哌嗪阻断RND型外排泵后，CAP18的MICs显著降低，但其他测试的cathelicidins的MICs没有降低。与这些数据高度相关的是，与同基因野生型菌株相比，SecDF基因敲除突变体的CAP18以及BMAP-27的MICs显著降低。此外，通过质粒互补重新引入克隆的secDF后，MIC值再次升高。这些结果表明SecDF参与了物种特异性cathelicidins对金黄色葡萄球菌的疗效降低。
