Department of Medical Microbiology, Radboud University Medical Center, Nijmegen, the Netherlands.
Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark.
Clin Microbiol Infect. 2021 Nov;27(11):1695.e1-1695.e6. doi: 10.1016/j.cmi.2021.03.028. Epub 2021 Apr 2.
Antimicrobial resistance among anaerobic bacteria is increasing, leading to a growing demand for inexpensive and reliable susceptibility testing methods. The aim of this study was to determine the suitability of Fastidious Anaerobe Agar (FAA) as a medium for disk diffusion for rapidly growing anaerobic bacteria.
Reproducibility of zone diameters and quality of growth were tested using six quality control (QC) strains. We compared four anaerobic incubation systems, two incubation temperatures (35°C and 37°C), and FAA from four manufacturers. The effect of incubation for 16-20 hours instead of 24 hours was tested on ten randomly selected isolates of the Bacteroides fragilis group. The final method was tested on 170 clinical B. fragilis-group isolates and compared to agar dilution MICs.
After 24 hours' incubation, all QC strains demonstrated confluent growth. The different anaerobic incubation systems were equal regarding quality of growth and zone diameters. Incubation at 35°C resulted in slightly larger zones (1-2 mm) than at 37°C. Except for Acumedia FAA, the different manufacturers showed good agreement in zone diameters. All B. fragilis-group isolates displayed confluent growth after 16-20 hours. Metronidazole inhibition zones correlated well with the reference MICs. There was an area of poorer separation for meropenem and piperacillin-tazobactam between 19-27 and 14-23 mm respectively. Prolonged incubation (40-44 h) of clindamycin resulted in better separation and the area of overlap was reduced from 13 to 8 mm compared with 16-20 hours' incubation.
FAA is a suitable medium for disk diffusion of these rapidly growing anaerobic bacteria.
由于厌氧细菌的抗药性不断增加，因此对廉价且可靠的药敏检测方法的需求也在不断增加。本研究旨在确定苛养厌氧菌琼脂（Fastidious Anaerobe Agar，FAA）作为快速生长的厌氧细菌纸片扩散法的适宜培养基。
使用 6 株质控菌株测试了抑菌圈直径的重现性和生长质量。我们比较了四种厌氧孵育系统、两种孵育温度（35°C 和 37°C）以及来自四个制造商的 FAA。还测试了在 16-20 小时而不是 24 小时孵育时对 10 株随机选择的脆弱拟杆菌群分离株的影响。最终方法在 170 株临床脆弱拟杆菌群分离株上进行了测试，并与琼脂稀释 MIC 进行了比较。
在 24 小时孵育后，所有质控菌株均表现出融合生长。不同的厌氧孵育系统在生长质量和抑菌圈直径方面没有差异。35°C 孵育时的抑菌圈直径比 37°C 略大（1-2mm）。除 Acumedia FAA 外，不同制造商的抑菌圈直径均具有良好的一致性。所有脆弱拟杆菌群分离株在 16-20 小时后均表现出融合生长。甲硝唑抑制圈与参考 MIC 相关性良好。美罗培南和哌拉西林-他唑巴坦的分离效果较差，分别为 19-27 和 14-23mm。与 16-20 小时孵育相比，延长克林霉素孵育时间（40-44 小时）可更好地区分，重叠面积从 13 毫米减少到 8 毫米。
FAA 是这些快速生长的厌氧细菌纸片扩散法的合适培养基。
