Center for Research in Health Technologies and Information Systems, Faculty of Medicine, University of Porto, Portugal.
School D. Maria II, Rua da Alegria, V.N. Famalicão, Portugal.
J Med Microbiol. 2014 Sep;63(Pt 9):1167-1173. doi: 10.1099/jmm.0.069609-0. Epub 2014 Jun 9.
Biofilms are commonly involved in medical device-related infections. The purpose of this study was to determine the antimicrobial and anti-biofilm activity of polyethyleneimine (PEI) and PEI-based nanoparticles (nanoPEI) against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii and Candida albicans (clinical and ATCC strains), and to evaluate their effect upon biofilm formation on polyurethane (PUR)-like catheters. MICs and minimal lethal concentrations of PEI and nanoPEI were determined according to CLSI microdilution reference protocols. For PEI, the MIC value was 195.31 mg l(-1) for all the bacteria and 48.83 mg l(-1) for the yeast strains. For nanoPEI, the MIC value was 1250 mg l(-1) for all the strains except A. baumannii, for which it was 2500 mg l(-1). Biofilm formation was assessed with PUR-like catheter segments and biofilm metabolic activity was quantified by colorimetry with a tetrazolium reduction assay. Plasma membrane integrity and membrane potential were assessed by flow cytometry after staining microbial cells with a membrane-impermeable dye, propidium iodide, and a membrane-potential marker, DiBAC4(3). PEI inhibited growth of all microbial species; higher concentrations of nanoPEI were needed to inhibit growth of all species. Biofilm formation in the presence of anti-bacterial PEI activity was dose-dependent (except for S. epidermidis) and species-related. NanoPEI at 0.5×MIC and MIC significantly reduced the metabolic activity of biofilms of S. aureus, S. epidermidis and A. baumannii, whereas 2×MIC was required in order to inhibit biofilm metabolic activity.
生物膜通常与医疗器械相关感染有关。本研究旨在确定聚乙烯亚胺（PEI）和基于聚乙烯亚胺的纳米粒子（nanoPEI）对金黄色葡萄球菌、表皮葡萄球菌、鲍曼不动杆菌和白色念珠菌（临床和 ATCC 株）的抗菌和抗生物膜活性，并评估它们对聚氨酯（PUR）样导管上生物膜形成的影响。根据 CLSI 微量稀释参考方案确定 PEI 和 nanoPEI 的 MIC 和最小致死浓度。对于 PEI，所有细菌的 MIC 值为 195.31 mg l(-1)，酵母菌株的 MIC 值为 48.83 mg l(-1)。对于 nanoPEI，除鲍曼不动杆菌外，所有菌株的 MIC 值均为 1250 mg l(-1)，而鲍曼不动杆菌的 MIC 值为 2500 mg l(-1)。使用 PUR 样导管段评估生物膜形成，并用四唑还原测定比色法定量生物膜代谢活性。用膜不可渗透染料碘化丙啶和膜电位标记物 DiBAC4(3)染色微生物细胞后，通过流式细胞术评估质膜完整性和膜电位。PEI 抑制所有微生物物种的生长；需要更高浓度的 nanoPEI 来抑制所有物种的生长。在具有抗细菌 PEI 活性的存在下，生物膜形成呈剂量依赖性（表皮葡萄球菌除外）并且与物种有关。nanoPEI 在 0.5×MIC 和 MIC 时显著降低金黄色葡萄球菌、表皮葡萄球菌和鲍曼不动杆菌生物膜的代谢活性，而要抑制生物膜代谢活性则需要 2×MIC。
