Department of Microbiology, Facultad de Ciencias Biológicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León CP 66450, Mexico.
Department of Infectious Diseases, Hospital Universitario "Dr. José E. González" y Facultad de Medicina, Universidad Autónoma de Nuevo León, Mitras Centro, Monterrey, Nuevo León CP 64460, Mexico.
J Microbiol Methods. 2022 Jul;198:106493. doi: 10.1016/j.mimet.2022.106493. Epub 2022 May 25.
Coagulase-negative Staphylococcus hominis causes bloodstream infections and often can form biofilms on medical devices. This study aimed to improve the current methodology for antimicrobial susceptibility testing (AST) in biofilm-growing S. hominis isolates. Biofilm production of S. hominis was assessed using the crystal violet staining method in trypticase soy broth supplemented with 1% glucose (TSB), Mueller-Hinton broth (MHB), or MHB using flat-bottom plates or the Calgary device. Susceptibility to antibiotics was assessed using the broth microdilution method (MHB and TSB) in planktonic cells (round-bottom plates) and biofilm cells (flat-bottom plates and the Calgary device). Biofilm determination using TSB yielded better performance over MHB, and flat-bottom plates without agitation were preferred over the Calgary device. Higher fold dilution values between the minimum biofilm eradication concentration (MBEC) and the minimum inhibitory concentration (MIC) were obtained in MHB for almost all antibiotics, except for linezolid. TSB and flat-bottom polystyrene plates were preferred over MHB and the Calgary device for biofilm determination. AST in biofilm-growing S. hominis showed better performance using TSB compared to MHB. Therefore, when comparing MBEC and MIC values, AST in planktonic cells could also be performed using TSB instead of MHB.
人凝固酶阴性葡萄球菌可引起血流感染，且常可在医疗器械上形成生物膜。本研究旨在改进现有的生物膜生长人凝固酶阴性葡萄球菌分离株的药敏试验（AST）方法。采用结晶紫染色法在添加 1%葡萄糖的胰蛋白酶大豆肉汤（TSB）、Mueller-Hinton 肉汤（MHB）或 MHB 中平皿或 Calgary 装置中评估人凝固酶阴性葡萄球菌的生物膜生成。采用肉汤微量稀释法（MHB 和 TSB）在浮游细胞（平底孔板）和生物膜细胞（平底孔板和 Calgary 装置）中评估抗生素的敏感性。与 MHB 相比，TSB 用于生物膜测定的效果更好，且无搅拌的平底孔板优于 Calgary 装置。除利奈唑胺外，几乎所有抗生素在 MHB 中的最低生物膜清除浓度（MBEC）与最低抑菌浓度（MIC）之间的稀释倍数都更高。与 MHB 和 Calgary 装置相比，TSB 和聚苯乙烯平皿更适合用于生物膜测定。与 MHB 相比，在生长生物膜的人凝固酶阴性葡萄球菌中，TSB 用于 AST 的效果更好。因此，在比较 MBEC 和 MIC 值时，也可使用 TSB 而不是 MHB 代替浮游细胞进行 AST。
