PDF(Pubmed)
Abstract：
NDM-producing carbapenem-resistant bacterial infections became a challenge for clinicians. Combination therapy of aztreonam and ceftazidime-avibactam is a prudent choice for these infections. However, there is still no recommendation of a practically feasible method for testing aztreonam and ceftazidime-avibactam synergy. We proposed a simple method for testing aztreonam and ceftazidime-avibactam synergy and compared it with reference broth micro-dilution and other methods. Carbapenem-resistant Enterobacterales clinical isolates were screened for the presence of the NDM gene by the Carba R test. NDM harbouring isolates were tested for aztreonam and ceftazidime-avibactam synergy by broth microdilution (reference method), E strip-disc diffusion, double disc diffusion, and disc replacement methods. In the newly proposed method, the MHA medium was supplemented with ceftazidime-avibactam (corresponding to an aztreonam concentration of 4μg/ml). The MHA medium was then inoculated with the standard inoculum (0.5 McFarland) of the test organism. An AZT disc (30 μg) was placed on the supplemented MHA medium, and the medium was incubated overnight at 37°C. Aztreonam zone diameter on the supplemented MHA medium (in the presence of ceftazidime-avibactam) was compared with that from a standard disc diffusion plate (without ceftazidime-avibactam), performed in parallel. Interpretation of synergy was based on the restoration of aztreonam zone diameter (in the presence of ceftazidime-avibactam) crossing the CLSI susceptibility breakpoint, i.e., ≥ 21 mm. Of 37 carbapenem-resistant NDM-producing isolates, 35 (94.6%) were resistant to aztreonam and tested synergy positive by the proposed method. Its sensitivity and specificity were 97.14% and 100%, respectively. Cohen\'s kappa value showed substantial agreement of the reference method with the proposed method (κ = 0.78) but no other methods. The proposed method is simple, easily interpretable, and showed excellent sensitivity, specificity, and agreement with the reference method. Therefore, the new method is feasible and reliable for testing aztreonam synergy with avibactam in NDM-producing Enterobacterales.
摘要：
产生NDM的碳青霉烯类耐药细菌感染成为临床医生面临的挑战。氨曲南和头孢他啶-阿维巴坦的联合治疗是这些感染的谨慎选择。然而,目前还没有推荐一种切实可行的方法来检测氨曲南和头孢他啶-阿维巴坦的协同作用.我们提出了一种测试氨曲南和头孢他啶-阿维巴坦协同作用的简单方法，并将其与参考肉汤微量稀释和其他方法进行了比较。通过CarbaR试验筛选了耐碳青霉烯类肠杆菌临床分离株中是否存在NDM基因。通过肉汤微量稀释（参考方法）测试了携带NDM的分离株的氨曲南和头孢他啶-阿维巴坦的协同作用，E带盘扩散，双盘扩散，和椎间盘更换方法。在新提出的方法中，MHA培养基补充有头孢他啶-阿维巴坦(对应于4μg/ml的氨曲南浓度)。然后用测试生物体的标准接种物(0.5McFarland)接种MHA培养基。将AZT圆盘（30μg）置于补充的MHA培养基上，并将培养基在37°C下孵育过夜。将补充的MHA培养基（在头孢他啶-阿维巴坦存在下）上的氨曲南区直径与标准圆盘扩散板（不含头孢他啶-阿维巴坦）的直径进行比较，并行执行。协同作用的解释是基于氨曲南区域直径的恢复（在头孢他啶-阿维巴坦的存在下）穿过CLSI敏感性断点，即，≥21mm。在37株耐碳青霉烯类NDM的分离株中，35（94.6％）对氨曲南具有抗性，并通过所提出的方法检测出协同作用呈阳性。其敏感性和特异性分别为97.14%和100%,分别。Cohen的kappa值表明参考方法与所提出的方法（κ=0.78）基本一致，但没有其他方法。该方法简单,易于解释，并显示出优异的灵敏度，特异性，并与参考方法一致。因此,该新方法可用于检测氨曲南与阿维巴坦在产NDM肠杆菌中的协同作用。
