Bennion R S, Williams R A, Wilson S E
Surgery. 1984 Jan;95(1):22-6.
The current technique for investigating the response of vascular prosthetic material to infection is by challenge with a sublethal dose of bacteria, usually an intravenous infusion of 10(8) organisms in an animal model. This large bacterial inoculum, however, obscures any difference in the infectibility of prostheses that may be inherent in the material, its incorporation into host tissues, or its modification by antibiotic impregnation, all of which are clinically important in resistance to infection. We have developed a sensitive method for determination of the susceptibility to infection of vascular prostheses based on calculation of the number of bacteria required to infect a specific prosthesis in 50% of trials (ID50). Following implantation of the prosthesis to be tested in the canine infrarenal aorta, a dose-response curve was calculated by the intravenous infusion of known inocula of S. aureus (at log intervals from 10(2) to 10(8) bacteria). At 6 weeks, the prosthesis was harvested and cultured to document infection with S. aureus. A characteristic sigmoid curve Kesulted, from which the ID50 was determined. To test this method, a comparison was made between commercial human umbilical vein graft (HUVG), HUVG impregnated with silver sulfadiazine, and double-velour Dacron in 60 dogs. Although all prostheses were infected by the standard 10(8) inoculum, an approximately tenfold increase in the resistance to infection between treated and untreated HUVG (less than 10(2) to 10(2.8) and a fourfold increase in resistance between treated HUVG and double-velour Dacron (10(2.8) to 10(3.2] was demonstrated in the dose-response curves. Since the number of bacteria in postimplant bacteremia rarely exceeds 10(2) organisms/ml, such differences in infectibility can be clinically significant. ID50 determination provides a sensitive, reproducibleble method for quantitating resistance to infection in vascular prostheses.
目前研究血管修复材料对感染反应的技术是用亚致死剂量的细菌进行攻击，通常是在动物模型中静脉注射10⁸个生物体。然而，这种大量的细菌接种掩盖了修复材料本身可能固有的、其与宿主组织结合或经抗生素浸渍改性后在感染性方面的任何差异，而所有这些在抗感染方面在临床上都很重要。我们已经开发出一种灵敏的方法，用于根据在50%的试验中感染特定修复体所需的细菌数量（半数感染剂量，ID50）来测定血管修复体对感染的易感性。在将待测试的修复体植入犬肾下腹主动脉后，通过静脉注射已知接种量的金黄色葡萄球菌（从10²到10⁸个细菌，以对数间隔）来计算剂量反应曲线。6周后，取出修复体并进行培养，以记录金黄色葡萄球菌感染情况。得到了一条特征性的S形曲线，据此确定ID50。为了测试该方法，在60只狗身上对商用人类脐静脉移植物（HUVG）、浸渍磺胺嘧啶银的HUVG和双绒涤纶进行了比较。尽管所有修复体都被标准的10⁸接种量感染，但在剂量反应曲线中显示，处理过的和未处理的HUVG之间的抗感染能力增加了约10倍（从少于10²到10².⁸），处理过的HUVG和双绒涤纶之间的抗感染能力增加了4倍（从10².⁸到10³.²）。由于植入后菌血症中的细菌数量很少超过10²个生物体/毫升，这种感染性的差异在临床上可能具有重要意义。ID50测定为定量评估血管修复体的抗感染能力提供了一种灵敏、可重复的方法。
