Bianco Gabriele, Boattini Matteo, Comini Sara, Banche Giuliana, Cavallo Rossana, Costa Cristina
Microbiology and Virology Unit, University Hospital Città della Salute e della Scienza di Torino, 10126 Turin, Italy.
Department of Public Health and Paediatrics, University of Torino, 10124 Turin, Italy.
Antibiotics (Basel). 2023 Mar 17;12(3):604. doi: 10.3390/antibiotics12030604.
Cefiderocol susceptibility testing represents a major challenge for clinical microbiology. Although disc diffusion showed robustness to test cefiderocol susceptibility, large areas of technical uncertainty (ATU) are reported by current EUCAST breakpoints. Herein, we evaluated the in vitro activity of cefiderocol on a collection of 286 difficult-to-treat Gram-negative isolates using disc diffusion and ComASP cefiderocol microdilution panel. Broth microdilution (BMD) in iron-depleted Mueller-Hinton broth was used as reference method. Following the EUCAST guidelines, disc diffusion allowed to determine cefiderocol susceptibility (susceptible or resistant) in 78.6%, 88.1%, 85.4% and 100% of Enterobacterales, , and isolates tested, respectively. ComASP cefiderocol panel showed 94% and 84% of overall categorical agreement and essential agreement. Only one very major error and two major errors were observed, for MIC values nearly close to the resistance breakpoint (2 mg/L). Overall, 20.5% of the carbapenemase-producing Enterobacterales that achieved ATU results by the disc diffusion method tested resistant by both ComASP panel and reference BMD. Conversely, all VIM-producing showed MIC values in the susceptible range (≤2 mg/L). Lastly, only six out of seven (85.7%) isolates showing inhibition zones <17 mm tested resistant by both ComASP panel and the reference BMD suggesting that inhibition zone <17 mm are not unequivocally suggestive of resistance. Our results, although obtained on a limited number of isolates, suggest that the combination of disc diffusion with a ComASP cefiderocol microdilution panel could be a viable solution to overcome the challenge of cefiderocol susceptibility testing in routine microbiology laboratories.
头孢地尔药敏试验是临床微生物学面临的一项重大挑战。尽管纸片扩散法在检测头孢地尔药敏方面表现出稳健性，但根据当前欧盟CAST标准，存在大面积技术不确定性（ATU）的报告。在此，我们使用纸片扩散法和ComASP头孢地尔微量稀释板，评估了头孢地尔对286株难治性革兰氏阴性菌的体外活性。以缺铁的 Mueller-Hinton 肉汤中的肉汤微量稀释法（BMD）作为参考方法。按照欧盟CAST指南，纸片扩散法分别在78.6%、88.1%、85.4%和100%的测试肠杆菌科细菌、铜绿假单胞菌、鲍曼不动杆菌和嗜麦芽窄食单胞菌中确定了头孢地尔的药敏情况（敏感或耐药）。ComASP头孢地尔平板显示总体分类一致性和基本一致性分别为94%和84%。仅观察到1个非常重大错误和2个重大错误，这些错误对应的 MIC 值接近耐药断点（2 mg/L）。总体而言，通过纸片扩散法得出ATU结果的产碳青霉烯酶肠杆菌科细菌中，有20.5%经ComASP平板和参考BMD检测均为耐药。相反，所有产VIM酶的菌株的MIC值均在敏感范围内（≤2 mg/L）。最后，在7株抑菌圈<17 mm的嗜麦芽窄食单胞菌中，只有6株（85.7%）经ComASP平板和参考BMD检测均为耐药，这表明抑菌圈<17 mm并不能明确提示耐药。我们的结果虽然是在有限数量的菌株上获得的，但表明纸片扩散法与ComASP头孢地尔微量稀释板相结合可能是克服常规微生物实验室中头孢地尔药敏试验挑战的可行解决方案。
