Chuard C, Vaudaux P, Waldvogel F A, Lew D P
Division of Infectious Diseases, University Hospital, Geneva, Switzerland.
Antimicrob Agents Chemother. 1993 Apr;37(4):625-32. doi: 10.1128/AAC.37.4.625.
Several recent studies have shown that bacteria either grown in vitro as adherent biofilms or recovered from infected prosthetic devices have decreased susceptibilities to antimicrobial killing. To further study the microbial and environmental factors responsible for this decreased antibiotic susceptibility, we developed an in vitro model of surface-adherent Staphylococcus aureus growing on polymethylmethacrylate coverslips coated with pure fibronectin. After exponential growth for 4 h, the population of fibronectin-attached S. aureus remained constant for a further 48-h period, as evaluated by CFU counts of organisms quantitatively removed from the coverslips. At selected time points, surface-bound organisms were exposed to bactericidal concentrations of either oxacillin, vancomycin, fleroxacin, or gentamicin in short-term (0.5 to 2 h) or long-term (24 h) killing assays. Whereas at 2 h surface-growing organisms were still optimally killed by all antimicrobial agents, at 4 and 24 h attached bacteria expressed markedly altered susceptibilities to these agents. The decrease in susceptibility was moderate for fleroxacin, more important for oxacillin and vancomycin, and extensive for gentamicin. When surface-attached S. aureus was compared with bacteria grown in a fluid phase, both populations showed a parallel time-dependent decrease in their susceptibilities to either oxacillin, vancomycin, or fleroxacin. In contrast, attached organisms became considerably more resistance to gentamicin than suspended bacteria did. Subpopulations of organisms spontaneously released from coverslips during antibiotic exposure also showed markedly reduced susceptibilities to antimicrobial killing. This simple model of S. aureus colonization of in vitro fibronectin-coated surfaces might represent a useful approach to the study of the physiological and biochemical changes that underlie the decreased antibiotic susceptibilities of biomaterial-attached organisms.
最近的几项研究表明，无论是在体外作为附着生物膜生长的细菌，还是从感染的假体装置中分离出的细菌，对抗菌杀灭的敏感性都有所降低。为了进一步研究导致这种抗生素敏感性降低的微生物和环境因素，我们建立了一种体外模型，即金黄色葡萄球菌在涂有纯纤连蛋白的聚甲基丙烯酸甲酯盖玻片上形成表面附着生长。通过对从盖玻片上定量去除的生物体进行CFU计数评估，在指数生长4小时后，附着在纤连蛋白上的金黄色葡萄球菌数量在接下来的48小时内保持恒定。在选定的时间点，将表面结合的生物体在短期（0.5至2小时）或长期（24小时）杀灭试验中暴露于杀菌浓度的苯唑西林、万古霉素、氟罗沙星或庆大霉素。虽然在2小时时，表面生长的生物体仍能被所有抗菌剂最佳杀灭，但在4小时和24小时时，附着的细菌对这些药物的敏感性明显改变。氟罗沙星的敏感性降低程度适中，苯唑西林和万古霉素更为明显，庆大霉素则非常显著。当将表面附着的金黄色葡萄球菌与在液相中生长的细菌进行比较时，两个群体对苯唑西林、万古霉素或氟罗沙星的敏感性均呈现出平行的时间依赖性下降。相比之下，附着的生物体对庆大霉素的耐药性比悬浮细菌显著增强。在抗生素暴露期间从盖玻片上自发释放的生物体亚群对抗菌杀灭的敏感性也明显降低。这种金黄色葡萄球菌在体外纤连蛋白包被表面定殖的简单模型可能是研究生物材料附着生物体抗生素敏感性降低背后的生理和生化变化的有用方法。
