Comparative assessment of antibiotic susceptibility of coagulase-negative staphylococci in biofilm versus planktonic culture as assessed by bacterial enumeration or rapid XTT colorimetry
Comparative assessment of antibiotic susceptibility of coagulase-negative staphylococci in biofilm versus planktonic culture as assessed by bacterial enumeration or rapid XTT colorimetry
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DOI：
10.1093/jac/dki217
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发表时间：
2005-08-01
影响因子：
5.2
通讯作者：
Azeredo, J
中科院分区：
文献类型：
--
作者：
Cerca, N;Martins, S;Azeredo, J
目的：定量比较凝固酶阴性葡萄球菌(CONS)、表皮葡萄球菌和溶血葡萄球菌所形成的生物膜与浮游细菌的药敏情况。方法：对几株CONS菌株进行浮游培养和生物膜培养，以确定生长方式对不同作用机制的抗生素敏感性的影响。通过与标准细菌计数技术的比较，测试了一种基于四唑盐还原(XTT)的新的快速比色法测量细胞活力的有效性。在双氯西林、头孢唑林、万古霉素、四环素和利福平的血药浓度峰值下进行6h的动力学研究。结果：在浮游细胞中，细胞壁合成的抑制剂在3h内非常有效。生物膜比浮游生物培养物对所有测试的抗生素，特别是细胞壁合成的抑制剂的敏感性要低得多。生物膜表型对蛋白质和RNA合成抑制剂的敏感性影响较小。标准细菌计数技术和XTT方法在生物膜和浮游生物膜检测中都得到了相同的结果。结论：本研究提供了浮游细菌和生物膜细菌对抗生素敏感性的更准确的比较，因为这两种细菌的细胞密度相似，而且我们测量了抑制细菌代谢所需的浓度，而不是根除整个细菌种群所需的浓度。虽然生物膜表型对靶向细胞壁合成的抗生素高度耐药，但对靶向RNA和蛋白质合成的抗生素相当敏感。
Objectives: To quantitatively compare the antibiotic susceptibility of biofilms formed by the coagulase-negative staphylococci (CoNS) Staphylococcus epidermidis and Staphylococcus haemolyticus with the susceptibility of planktonic cultures.Methods: Several CoNS strains were grown planktonically or as biofilms to determine the effect of the mode of growth on the level of susceptibility to antibiotics with different mechanisms of action. The utility of a new, rapid colorimetric method that is based on the reduction of a tetrazolium salt (XTT) to measure cell viability was tested by comparison with standard bacterial enumeration techniques. A 6 h kinetic study was performed using dicloxacillin, cefazolin, vancomycin, tetracycline and rifampicin at the peak serum concentration of each antibiotic.Results: In planktonic cells, inhibitors of cell wall synthesis were highly effective over a 3 h period. Biofilms were much less susceptible than planktonic cultures to all antibiotics tested, particularly inhibitors of cell wall synthesis. The susceptibility to inhibitors of protein and RNA synthesis was affected by the biofilm phenotype to a lesser degree. Standard bacterial enumeration techniques and the XTT method produced equivalent results both in biofilms and planktonic assays.Conclusions: This study provides a more accurate comparison between the antibiotic susceptibilities of planktonic versus biofilm populations, because the cell densities in the two populations were similar and because we measured the concentration required to inhibit bacterial metabolism rather than to eradicate the entire bacterial population. While the biofilm phenotype is highly resistant to antibiotics that target cell wall synthesis, it is fairly susceptible to antibiotics that target RNA and protein synthesis.