Aldridge K E, Sanders C V
Louisiana State University Medical Center, New Orleans 70112.
J Clin Microbiol. 1987 Dec;25(12):2317-21. doi: 10.1128/jcm.25.12.2317-2321.1987.
The susceptibilities of 36 isolates of the Bacteroides fragilis group to ceftizoxime, cefoxitin, clindamycin, and metronidazole were determined by using the National Committee for Clinical Laboratory Standards agar dilution reference method and a broth microdilution method using anaerobe, brucella, Schaedler, and brain heart infusion broths. MICs that were greater than or equal to fourfold higher or lower than those of the reference method were considered significant. Major and minor discrepancies in susceptibility interpretation (SI) were also noted. Ceftizoxime showed the greatest number of variations and SI discrepancies. In 72% of the cases, MICs in broth were greater than or equal to fourfold lower than those obtained by the reference method, resulting in 33% of the major and 22% of the minor discrepancies in SI. A total of 53% of the isolates were resistant to ceftizoxime by the reference method, but only 11 to 17% were resistant in the various broths. Significant variations in MICs of cefoxitin occurred in 19 to 22% of the isolates; 17 to 19% of the isolates showed major discrepancies and 31 to 58% showed minor discrepancies in SI. A total of 58% of the isolates were resistant to cefoxitin by the reference method, but only 19 to 28% were resistant in the various broths. Significant variations with clindamycin in broths ranged from 32 to 53% and resulted in 3 to 8% of the isolates showing major discrepancies and 33 to 44% showing minor discrepancies in SI. Metronidazole yielded significant variations in MICs in 6 to 28% of the isolates, but no major or minor SI discrepancies were noted. This study indicates that significant differences in susceptibility results, which appear to be method related, can result when isolates of the B. fragilis group are tested. Therefore, studies correlating in vitro results, determined by various methods, to clinical outcome are essential.
采用美国国家临床实验室标准委员会琼脂稀释参考方法以及使用厌氧菌肉汤、布鲁氏菌肉汤、沙氏肉汤和脑心浸液肉汤的肉汤微量稀释法，测定了36株脆弱拟杆菌属菌株对头孢唑肟、头孢西丁、克林霉素和甲硝唑的敏感性。将高于或低于参考方法四倍及以上的最低抑菌浓度（MIC）视为有显著差异。还记录了药敏结果判读（SI）中的主要和次要差异。头孢唑肟显示出最多的差异和SI差异。在72%的病例中，肉汤中的MIC比参考方法获得的结果低四倍及以上，导致33%的主要和22%的次要SI差异。通过参考方法，共有53%的分离株对头孢唑肟耐药，但在各种肉汤中只有11%至17%耐药。19%至22%的分离株头孢西丁的MIC出现显著差异；17%至19%的分离株在SI中显示主要差异，31%至58%显示次要差异。通过参考方法，共有58%的分离株对头孢西丁耐药，但在各种肉汤中只有19%至28%耐药。肉汤中克林霉素的显著差异范围为32%至53%，导致3%至8%的分离株在SI中显示主要差异，33%至44%显示次要差异。甲硝唑在6%至28%的分离株中MIC出现显著差异，但未发现主要或次要的SI差异。本研究表明，对脆弱拟杆菌属菌株进行检测时，药敏结果可能存在显著差异，这似乎与方法有关。因此，将通过各种方法测定的体外结果与临床结果相关联的研究至关重要。
