Boyce J M, White R L, Bonner M C, Lockwood W R
J Clin Microbiol. 1982 Feb;15(2):220-5. doi: 10.1128/jcm.15.2.220-225.1982.
The MS-2 system (Abbott Diagnostics, Division of Abbott Laboratories, Dallas, Tex.) is an automated system capable of rapid antimicrobial susceptibility testing. However, the short incubation periods used by the device may adversely affect its ability to detect slowly growing resistant organisms. Shortly after the introduction of the MS-2 system into the University of Mississippi Medical Center clinical microbiology laboratory, we noted discrepancies between the MS-2 and the disk diffusion susceptibility reports when methicillin-resistant Staphylococcus aureus isolates were tested. Subsequently, we determined the susceptibilities of 75 such isolates by the MS-2 and Kirby-Bauer disk diffusion methods and measured the minimum inhibitory concentrations of methicillin, oxacillin, and cephalothin for 33 of the 75 isolates by standardized agar dilution techniques. There was only 47% overall agreement between the MS-2 and disk diffusion methods when methicillin was tested and 15% agreement when cephalothin was the test drug. There was 93% or more overall agreement between the two methods when other antimicrobial agents were tested. The minimum inhibitory concentration of methicillin was greater than or equal to 16 micrograms/ml for all 33 isolates evaluated by the agar dilution method. A comparison of the MS-2 and agar dilution results revealed an overall agreement of 49% when the susceptibilities to methicillin were determined. The MS-2 system reported that multiple methicillin-resistant S. aureus isolates obtained from a single patient were either resistant, intermediate, or sensitive to methicillin. Inconsistent results were also obtained when a single isolate was tested simultaneously in 10 cuvette cartridges. We conclude that the MS-2 system does not reliably detect methicillin and cephalothin resistance among S. aureus.
MS-2系统（雅培诊断公司，雅培实验室旗下部门，得克萨斯州达拉斯）是一种能够进行快速抗菌药敏试验的自动化系统。然而，该设备使用的短培养时间可能会对其检测生长缓慢的耐药菌的能力产生不利影响。在将MS-2系统引入密西西比大学医学中心临床微生物实验室后不久，我们注意到在检测耐甲氧西林金黄色葡萄球菌分离株时，MS-2系统和纸片扩散法药敏报告之间存在差异。随后，我们通过MS-2系统和 Kirby-Bauer 纸片扩散法确定了75株此类分离株的药敏情况，并通过标准化琼脂稀释技术测量了其中33株分离株对甲氧西林、苯唑西林和头孢噻吩的最低抑菌浓度。检测甲氧西林时，MS-2系统和纸片扩散法的总体一致性仅为47%，以头孢噻吩为测试药物时一致性为15%。检测其他抗菌药物时，两种方法的总体一致性达到93%或更高。通过琼脂稀释法评估的所有33株分离株对甲氧西林的最低抑菌浓度均大于或等于16微克/毫升。比较MS-2系统和琼脂稀释法的结果发现，确定对甲氧西林的药敏情况时，总体一致性为49%。MS-2系统报告称，从一名患者身上获得的多株耐甲氧西林金黄色葡萄球菌分离株对甲氧西林的耐药性、中介性或敏感性各不相同。在10个比色皿盒中同时检测单个分离株时也得到了不一致的结果。我们得出结论，MS-2系统不能可靠地检测金黄色葡萄球菌对甲氧西林和头孢噻吩的耐药性。
