Huang A H, Wu J J, Weng Y M, Ding H C, Chang T C
Division of Clinical Microbiology, Department of Pathology, National Cheng Kung University Hospital, Taiwan, Republic of China.
J Clin Microbiol. 1998 Oct;36(10):2882-6. doi: 10.1128/JCM.36.10.2882-2886.1998.
Nonfastidious aerobic gram-negative bacilli (GNB) are commonly isolated from blood cultures. The feasibility of using an electrochemical method for direct antimicrobial susceptibility testing of GNB in positive blood cultures was evaluated. An aliquot (10 microliter) of 1:10-diluted positive blood cultures containing GNB was inoculated into the Bactometer module well (bioMérieux Vitek, Hazelwood, Mo.) containing 1 ml of Mueller-Hinton broth supplemented with an antibiotic. Susceptibility tests were performed in a breakpoint broth dilution format, with the results being categorized as resistant, intermediate, or susceptible. Seven antibiotics (ampicillin, cephalothin, gentamicin, amikacin, cefamandole, cefotaxime, and ciprofloxacin) were used in this study, with each agent being tested at the two interpretive breakpoint concentrations. The inoculated modules were incubated at 35 degreesC, and the change in impedance in each well was continuously monitored for 24 h by the Bactometer. The MICs of the seven antibiotics for each blood isolate were also determined by the standardized broth microdilution method. Of 146 positive blood cultures (1,022 microorganism-antibiotic combinations) containing GNB tested by the direct method, the rates of very major, major, and minor errors were 0, 1.1, and 2.5%, respectively. The impedance method was simple; no centrifugation, preincubation, or standardization of the inocula was required, and the susceptibility results were normally available within 3 to 6 h after inoculation. The rapid method may allow proper antimicrobial treatment almost 30 to 40 h before the results of the standard methods are available.
非苛养需氧革兰氏阴性杆菌（GNB）通常从血培养物中分离得到。评估了使用电化学方法对阳性血培养物中的GNB进行直接药敏试验的可行性。将10微升1:10稀释的含有GNB的阳性血培养物接种到含有1毫升补充了抗生素的Mueller-Hinton肉汤的Bactometer模块孔（生物梅里埃公司，密苏里州黑兹尔伍德）中。药敏试验采用断点肉汤稀释法进行，结果分为耐药、中介或敏感。本研究使用了七种抗生素（氨苄西林、头孢噻吩、庆大霉素、阿米卡星、头孢孟多、头孢噻肟和环丙沙星），每种药物在两个解释性断点浓度下进行测试。接种后的模块在35℃下孵育，Bactometer连续监测每个孔中阻抗的变化24小时。每种血培养分离株的七种抗生素的最低抑菌浓度（MIC）也通过标准化肉汤微量稀释法测定。通过直接法检测的146份含有GNB的阳性血培养物（1022种微生物-抗生素组合）中，极重大、重大和微小错误率分别为0%、1.1%和2.5%。阻抗法简单；无需离心、预孵育或对接种物进行标准化，药敏结果通常在接种后3至6小时内即可获得。这种快速方法可能使在标准方法结果出来前近30至40小时就能进行适当的抗菌治疗。
