To assess the performance of the drop test for polymyxin B resistance detection among Enterobacterales and non‐fermentative gram‐negative rods resistant to carbapenems. Seven hundred and fifteen carbapenem‐resistant isolates were tested: 628 Enterobacterales species and 87 non‐fermentative gram‐negative rods. For the polymyxin drop test, concentrations range from 0.25 to 8.0 µg/mL. Broth microdilution, as gold standard, was performed using in‐house‐prepared panels and interpreted according to the CLSI guidelines. Results were interpreted in terms of categorical agreements and discrepancies. Accuracy for a drop of polymyxin B at 2.0, 4.0 and 8.0 was calculated as better cutoff for resistance determination. No very major error was observed among all isolates, and 95.5% of agreement was observed among Enterobacterales, particularly for Klebsiella pneumoniae. A higher accuracy (95.1%) was obtained when a single drop of polymyxin B at 4.0 μg/mL was applied. Polymyxin drop test presented >95% of categorical agreement, without very major errors, for KPC‐producing K. pneumoniae isolates. An accuracy of 95.1% was obtained with a single drop at 4.0 μg/mL polymyxin B. Polymyxin B drop is an easy and feasible test and may allow a reduction on the turnaround time for polymyxin resistance detection and impacting on early implementation of accurate therapeutic interventions.

中文翻译：

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对非发酵革兰阴性棒和对碳青霉烯类耐药的肠杆菌中的多粘菌素抗性检测进行多粘菌素滴定试验的评估

评估肠杆菌和对碳青霉烯类耐药的非发酵革兰氏阴性棒中多粘菌素B耐药性下降试验的性能。测试了715个对碳青霉烯类耐药的菌株：628种肠杆菌和87种非发酵革兰氏阴性菌。对于多粘菌素滴落试验，浓度范围为0.25至8.0 µg / mL。肉汤微量稀释作为金标准，使用内部准备的面板进行，并根据CLSI指南进行解释。结果按照分类协议和差异进行解释。计算出多粘菌素B在2.0、4.0和8.0下降的准确度，是确定抗药性的更好的临界值。在所有分离株中均未观察到非常重大的错误，肠杆菌之间观察到95.5％的一致性，特别是对于肺炎克雷伯菌。当应用4.0μg/ mL的一滴多粘菌素B时，可获得更高的准确度（95.1％）。对于生产KPC的肺炎克雷伯菌分离株，多粘菌素滴落试验显示了> 95％的分类一致性，没有很大的重大错误。一次滴加多粘菌素B的滴度为4.0μg/ mL时，可达到95.1％的准确度。多粘菌素B滴是一种简单而可行的测试，可减少多粘菌素耐药性检测的周转时间，并影响早期实施准确的治疗性干预措施。