Canadian Blood Services, Ottawa, Ontario, Canada.
Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada.
J Med Microbiol. 2013 Jul;62(Pt 7):1051-1059. doi: 10.1099/jmm.0.050500-0. Epub 2013 Apr 4.
Bacterial contamination of platelet concentrates (PCs) poses the greatest infectious risk in modern transfusion medicine despite the implementation of measures such as improved skin disinfection and first aliquot diversion. The majority of PC contaminants are commensal skin flora introduced by venipuncture at the time of blood collection. The predominant organisms are Gram-positive coagulase-negative staphylococci such as Staphylococcus capitis. This bacterium has been implicated in numerous instances of infection and sepsis, likely for its ability to form surface-associated communities of micro-organisms encased in extracellular materials, known as biofilms. In the present study, five strains of S. capitis isolated from contaminated PCs were assessed for their ability to produce extracellular polysaccharide (slime), a canonical indicator of biofilm-formation ability, on Congo red agar plates. Biofilm formation was evaluated in both glucose-enriched trypticase soy broth (TSBg) and in PCs by using a crystal violet staining assay. The chemical nature of the biofilms was evaluated by disruption assays using sodium metaperiodate and proteinase K. In addition, biofilm architecture was observed by scanning electron microscopy. The presence of the biofilm-associated icaR and icaADBC genes was also examined by PCR. While only two out of the five S. capitis strains formed biofilms in TSBg, all strains formed biofilms in PCs. The ability of strains to produce extracellular polysaccharide and their possession of wild-type ica genes were not exclusive predictors of biofilm formation in TSBg or PCs; different profiles of biofilm markers were observed among isolates. This is likely due to the proteinaceous composition of the S. capitis biofilm matrix. Interestingly, an ica-negative, non-slime-producing isolate was capable of biofilm formation in PCs. Together, these data indicate that the platelet storage environment stimulates biofilm formation in S. capitis in the absence of extracellular polysaccharide production and that multiple bacterial factors and regulatory elements are likely involved in biofilm formation in this milieu.
血小板浓缩物 (PC) 的细菌污染尽管采取了改进皮肤消毒和第一份等分转移等措施，但仍是现代输血医学中最大的感染风险。大多数 PC 污染物是在采血时静脉穿刺引入的共生皮肤菌群。主要的生物体是革兰氏阳性凝固酶阴性葡萄球菌，如表皮葡萄球菌。这种细菌在许多感染和败血症的情况下都被牵连在内，可能是因为它能够形成被细胞外物质包裹的微生物表面相关群落，即生物膜。在本研究中，从污染的 PC 中分离出的五株表皮葡萄球菌菌株被评估其在刚果红琼脂平板上产生细胞外多糖 (粘液) 的能力，粘液是生物膜形成能力的典型指标。通过结晶紫染色测定法在富含葡萄糖的胰蛋白酶大豆肉汤 (TSBg) 和 PC 中评估生物膜形成。通过使用偏亚硫酸钠和蛋白酶 K 破坏测定法评估生物膜的化学性质。此外，通过扫描电子显微镜观察生物膜结构。还通过 PCR 检查了与生物膜相关的 icaR 和 icaADBC 基因的存在。虽然五株表皮葡萄球菌菌株中只有两株在 TSBg 中形成生物膜，但所有菌株在 PC 中都形成了生物膜。菌株产生细胞外多糖的能力及其携带野生型 ica 基因并不是在 TSBg 或 PC 中形成生物膜的唯一预测因子；在分离株中观察到不同的生物膜标记物谱。这可能是由于表皮葡萄球菌生物膜基质的蛋白质组成。有趣的是，一种 ica 阴性、不产粘液的分离株能够在 PC 中形成生物膜。这些数据表明，血小板储存环境在不产生细胞外多糖的情况下刺激表皮葡萄球菌生物膜的形成，并且在这种环境中，可能涉及多种细菌因素和调节元件。
