Jones R N, Barry A L, Fuchs P C, Allen S D
Clinical Microbiology Institute, Tualatin, Oregon.
Diagn Microbiol Infect Dis. 1987 Oct;8(2):87-94. doi: 10.1016/0732-8893(87)90154-4.
Ceftizoxime and cefoxitin (control) were tested against 99 anaerobic bacteria using three commonly used susceptibility testing methods. The cefoxitin MIC results with the National Committee for Clinical Laboratory Standards (NCCLS) reference agar dilution (RAD) method and the broth microdilution (BMD) method did not differ by more than one log2 dilution step. However, the ceftizoxime BMD MIC results were 2- to 4-fold lower than those produced by the RAD procedure. Broth disk elution (BDE) tests for both cephalosporins (ceftizoxime and cefoxitin) had very high rates of false-susceptible and false-resistant error when compared to the RAD MICs: the BDE tests are not recommended for either cephalosporin. Findings indicate that because of method and possible medium or technical variability, ceftizoxime MICs should be determined only by the NCCLS RAD method. Also, cefoxitin susceptibility should be assessed primarily by RAD or BMD procedures. This should minimize confusion related to ceftizoxime's spectrum and activity against anaerobic bacteria compared to similar beta-lactam drugs. Ceftizoxime quality control guidelines were established for Bacteroides fragilis (ATCC 25285): mode, 64 micrograms/ml, range 32-128 micrograms/ml. Other control strains were not reliable.
使用三种常用的药敏试验方法，对头孢唑肟和头孢西丁（对照）进行了针对99株厌氧菌的测试。采用美国国家临床实验室标准委员会（NCCLS）参考琼脂稀释（RAD）法和肉汤微量稀释（BMD）法得出的头孢西丁最低抑菌浓度（MIC）结果相差不超过一个log2稀释级。然而，头孢唑肟的BMD MIC结果比RAD法得出的结果低2至4倍。与RAD MIC相比，两种头孢菌素（头孢唑肟和头孢西丁）的肉汤纸片洗脱（BDE）试验出现假敏感和假耐药错误的发生率非常高：不推荐对任何一种头孢菌素采用BDE试验。研究结果表明，由于方法以及可能存在的培养基或技术差异，头孢唑肟的MIC仅应通过NCCLS RAD法来确定。此外，头孢西丁的药敏性应主要通过RAD或BMD程序进行评估。与类似的β-内酰胺类药物相比，这应能最大程度减少与头孢唑肟对厌氧菌的抗菌谱和活性相关的混淆。针对脆弱拟杆菌（ATCC 25285）制定了头孢唑肟质量控制指南：标准值，64微克/毫升，范围32 - 128微克/毫升。其他对照菌株不可靠。
