McCashion R N, Lynch W H
Department of Biology, University of New Brunswick, Fredericton, Canada.
Antimicrob Agents Chemother. 1987 Sep;31(9):1414-9. doi: 10.1128/AAC.31.9.1414.
In contrast to polymyxin B-susceptible gram-negative bacteria of human origin, the fish pathogen Aeromonas salmonicida was resistant to sensitization by polymyxin B nonapeptide (PMBN) to hydrophobic antibiotics. Similarly, sensitization of A. salmonicida strains by PMBN to the bactericidal action of brook trout (Salvelinus fontinalis) serum complement was less pronounced than the similar effect of PMBN against other gram-negative bacteria in certain mammalian sera. The surface array protein (A layer), overlying the outer membrane of virulent A. salmonicida strains, did not appear to cause resistance to PMBN sensitization since an A-layer-deficient mutant showed similar responses to PMBN as its parent strain. Electron micrographs of PMBN-treated A. salmonicida cells revealed very little visible outer membrane disruption when compared with the extensive blebbing on the outer membrane surface caused by PMBN in certain enteric bacteria, including Escherichia coli K-37. However, small extracellular vesiclelike components, which may have been derived from the outer membrane, were numerous around PMBN-treated A. salmonicida cells. In this connection, PMBN caused disruption of the A layer in the form of bulges, breaks, and detached fragments which appeared to be associated with the accumulation of these vesicles underneath the A layer of wild-type A. salmonicida strains.
与源自人类的对多粘菌素B敏感的革兰氏阴性菌不同，鱼类病原体杀鲑气单胞菌对多粘菌素B九肽（PMBN）介导的对疏水性抗生素的致敏具有抗性。同样，PMBN对杀鲑气单胞菌菌株对溪鳟（Salvelinus fontinalis）血清补体杀菌作用的致敏作用，不如PMBN对某些哺乳动物血清中其他革兰氏阴性菌的类似作用明显。在有毒力的杀鲑气单胞菌菌株外膜上覆盖的表面阵列蛋白（A层）似乎并未导致对PMBN致敏产生抗性，因为一个缺乏A层的突变体对PMBN的反应与其亲本菌株相似。与PMBN处理的某些肠道细菌（包括大肠杆菌K-37）外膜表面出现的广泛气泡相比，PMBN处理的杀鲑气单胞菌细胞的电子显微镜照片显示外膜几乎没有可见的破坏。然而，在PMBN处理的杀鲑气单胞菌细胞周围有许多可能源自外膜的小细胞外囊泡样成分。就此而言，PMBN导致A层以凸起、断裂和分离片段的形式破坏，这些似乎与野生型杀鲑气单胞菌菌株A层下方这些囊泡的积累有关。
