Hammerberg S, Marks M I, Weinmaster G
Antimicrob Agents Chemother. 1976 Dec;10(6):869-71. doi: 10.1128/AAC.10.6.869.
Lack of correlation between quantitative minimal inhibitory concentration (MIC) determinations and disk diffusion susceptibility tests in our laboratory prompted a study to reevaluate the use of the disk diffusion test for sulfonamide susceptibility testing of Neisseria meningitidis. One hundred and sixty-three recent clinical isolates of N. meningitidis were examined for sulfonamide susceptibility by the agar dilution and disk diffusion methods. Optimal inocula for each of the tests were determined, and thereafter all disk diffusion tests were compared with quantitative MICs as determined by the agar dilution method using sulfadiazine and an inoculum of 10(6) colony-forming units (CFU)/ml. The clearest and most reproducible zone diameters were obtained with a 10(7)-CFU/ml inoculum in the disk diffusion test. There was complete correlation between the disk zone diameters for 300-mug disks of sulfadiazine and sulfathiazole and the agar dilution test MICs. All isolates with a zone diameter of <20 mm were resistant to sulfadiazine, whereas those with zone diameters of >/=30 mm were susceptible. False susceptible and false resistant readings were obtained with 300-mug sulfisoxazole disks. These data suggest that inocula and type of sulfonamide are critical factors in the disk diffusion test for meningococcal susceptibility testing. Sulfonamide disks are not interchangeable for susceptibility testing of meningococci.
在我们实验室中，定量最小抑菌浓度（MIC）测定结果与纸片扩散药敏试验之间缺乏相关性，这促使我们开展一项研究，以重新评估纸片扩散试验用于脑膜炎奈瑟菌磺胺类药敏试验的适用性。采用琼脂稀释法和纸片扩散法对163株近期分离的脑膜炎奈瑟菌临床菌株进行磺胺类药敏检测。确定了每种试验的最佳接种量，此后，将所有纸片扩散试验结果与采用磺胺嘧啶及10(6)菌落形成单位（CFU）/ml接种量通过琼脂稀释法测定的定量MIC结果进行比较。在纸片扩散试验中，接种量为10(7)CFU/ml时可获得最清晰且重复性最好的抑菌圈直径。磺胺嘧啶和磺胺噻唑300μg纸片的抑菌圈直径与琼脂稀释试验的MIC结果完全相关。所有抑菌圈直径<20 mm的菌株对磺胺嘧啶耐药，而抑菌圈直径≥30 mm的菌株敏感。使用300μg磺胺异恶唑纸片时出现了假敏感和假耐药结果。这些数据表明，接种量和磺胺类药物类型是脑膜炎奈瑟菌药敏试验纸片扩散法中的关键因素。用于脑膜炎奈瑟菌药敏试验的磺胺类药敏纸片不能相互替换。
