Aldridge K E, Henderberg A, Schiro D D, Sanders C V
Department of Medicine, Louisiana State University Medical Center, New Orleans 70112.
J Clin Microbiol. 1990 Feb;28(2):375-8. doi: 10.1128/jcm.28.2.375-378.1990.
Susceptibility testing of 161 clinical isolates of the Bacteroides fragilis group was performed to compare interpretive results generated by the broth disk elution and broth microdilution methods recommended by the National Committee for Clinical Laboratory Standards. Among the cephalosporin-cephamycin compounds tested, correlation was poorest for ceftizoxime (71%), ceftriaxone (57%), and cefotaxime (47%); when the tests did not correlate, false resistance was seen 92, 95, and 93% of the time, respectively. Cefotetan and cefoperazone showed lack of correlation in 19 and 20% of the tests, respectively. For cefotetan, false resistance was more frequent, while with cefoperazone, false susceptibility occurred more often. Cefoxitin produced the fewest discrepancies; 10% of the disk elution tests produced either false-resistance or false-susceptibility results. Mezlocillin and piperacillin showed lack of correlation in 8 and 14% of the tests, respectively, and discrepancies were due primarily to false-resistance results. Overall with the beta-lactams, 84% of the discordant interpretive results were false resistance by the broth disk elution test. Clindamycin had a discrepancy rate of 10%, with the majority of discrepancies being false susceptibility disk elution results. Because of the high number of discrepancies noted with ceftizoxime, ceftriaxone, and cefotaxime, we recommend that these drugs not be tested by the disk elution method and that they be tested by a quantitative MIC method such as the broth microdilution test. Furthermore, caution should be exercised when interpreting broth disk elution results with all the beta-lactams included in this study except imipenem. These data indicate the lack of correlation of results between these two tests for many beta-lactams and suggest the need for a reexamination of the disk elution method to provide a more accurately standardized test.
对161株脆弱拟杆菌群临床分离株进行药敏试验，以比较美国国家临床实验室标准委员会推荐的肉汤纸片洗脱法和肉汤微量稀释法所产生的解释结果。在所测试的头孢菌素-头霉素类化合物中，头孢唑肟（71%）、头孢曲松（57%）和头孢噻肟（47%）的相关性最差；当试验结果不相关时，分别有92%、95%和93%的情况出现假耐药。头孢替坦和头孢哌酮分别在19%和20%的试验中显示缺乏相关性。对于头孢替坦，假耐药更为常见，而对于头孢哌酮，假敏感更为常见。头孢西丁产生的差异最少；10%的纸片洗脱试验产生了假耐药或假敏感结果。美洛西林和哌拉西林分别在8%和14%的试验中显示缺乏相关性，差异主要是由于假耐药结果。总体而言，对于β-内酰胺类药物，84%的不一致解释结果是肉汤纸片洗脱试验的假耐药。克林霉素的差异率为10%，大多数差异是纸片洗脱试验的假敏感结果。由于头孢唑肟、头孢曲松和头孢噻肟的差异数量较多，我们建议不要用纸片洗脱法对这些药物进行检测，而应采用定量MIC法，如肉汤微量稀释试验。此外，在解释本研究中除亚胺培南外的所有β-内酰胺类药物的肉汤纸片洗脱结果时应谨慎。这些数据表明，这两种试验对许多β-内酰胺类药物的结果缺乏相关性，并建议重新审视纸片洗脱法，以提供更准确标准化的试验。
