Colistin is considered as one of the last-resort antibiotics and reliable antimicrobial susceptibility testing is therefore crucial. The reference standard for AST according to EUCAST and CLSI is broth microdilution (BMD). However, BMD is labor intensive to perform. Commercial antimicrobial susceptibility tests derived from BMD method are available. We investigated the performance of four different commercial tests: Sensititre™, SensiTest™ Colistin, Micronaut MIC Strip Colistin and UMIC Colistin using 70 clinical isolates (half of them was deemed by VITEK2 as resistant), including isolates from cystic fibrosis patients and mcr-1 bearing isolates. We used two reference standards: BMD and composite MIC as determined by all four tests. Sensititre™ had essential agreement (EA, defined as minimum inhibitory concentration within ± 1 dilution) of 87% and 89% compared to BMD and composite reference standard, respectively. For SensiTest™, the EA’s were 93% and 90%. For UMIC, 87% and 90%, and for Micronaut, 83% and 84%. All four tests demonstrated categorical agreement (CA) above 90%. CA for SensiTest™ and Micronaut was both 96%, UMIC 94%, and Sensititre™ 93%. All tests were reproducible as tested in two quality control isolates. In conclusion, in clinical isolates from a large referral center, the four commercial tests for determination of colistin minimum inhibitory concentrations showed acceptable performance.

中文翻译：

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四种商业肉汤微量稀释试验在确定大肠菌素最低抑菌浓度中的准确性。

Colistin被认为是最后一种抗生素，因此可靠的抗菌药敏性测试至关重要。根据EUCAST和CLSI的AST参考标准是肉汤微稀释液（BMD）。但是，BMD的执行需要大量劳动。可以使用源自BMD方法的商业抗菌药敏试验。我们使用70种临床分离株（其中一半被VITEK2视为耐药），包括囊性纤维化患者和mcr-1分离株，研究了四种不同的商业测试的性能：Sensititre™，SensiTest™Colistin，Micronaut MIC Strip Colistin和UMIC Colistin。轴承隔离。我们使用了两个参考标准：由所有四个测试确定的BMD和复合MIC。Sensititre™具有基本协议（EA，定义为与BMD和复合参考标准相比分别为87％和89％的最小抑制浓度（±1稀释内）。对于SensiTest™，EA分别为93％和90％。对于UMIC，分别为87％和90％，对于Micronaut，则分别为83％和84％。所有这四个测试均显示超过90％的绝对一致性（CA）。SensiTest™和Micronaut的CA均为96％，UMIC为94％，Sensititre™为93％。如在两个质量控制分离物中进行测试，所有测试均具有可重复性。总之，在来自大型转诊中心的临床分离株中，四种用于测定大肠菌素最低抑菌浓度的商业测试显示出可接受的性能。所有这四个测试均显示超过90％的绝对一致性（CA）。SensiTest™和Micronaut的CA均为96％，UMIC为94％，Sensititre™为93％。如在两个质量控制分离物中进行测试，所有测试均具有可重复性。总之，在来自大型转诊中心的临床分离株中，四种用于测定大肠菌素最低抑菌浓度的商业测试显示出可接受的性能。所有这四个测试均显示超过90％的绝对一致性（CA）。SensiTest™和Micronaut的CA均为96％，UMIC为94％，Sensititre™为93％。如在两个质量控制分离物中进行测试，所有测试均具有可重复性。总之，在来自大型转诊中心的临床分离株中，四种用于测定大肠菌素最低抑菌浓度的商业测试显示出可接受的性能。