Service de Microbiologie et Hygiène Hospitalière, CHU Nîmes, Nîmes, France.
VBMI, INSERM U1047, Université de Montpellier, Service de Microbiologie et Hygiène Hospitalière, CHU Nîmes, Nîmes, France.
Front Cell Infect Microbiol. 2020 Sep 11;10:491. doi: 10.3389/fcimb.2020.00491. eCollection 2020.
Due to the importance of a rapid determination of patients infected by multidrug resistant bacteria, we evaluated two rapid diagnostic tests for the detection of third-generation cephalosporins (3GC)-resistant Enterobacterales directly from positive blood cultures within 1 h: BL-RED (electrochemical method) and β-LACTA test (chromogenic method). A panel of 150 clinical strains characterized for their resistance profiles (e.g., penicillinases, extended-spectrum beta-lactamases (ESBLs), overproduction of cephalosporinase, carbapenemases, impermeability) was tested. Approximately 100 CFU of each isolate was spiked into sterile blood culture bottles and incubated in a BD BACTEC FX automated system (Becton Dickinson, USA). Positive blood cultures were examined to parallel testing using the BL-RED and β-LACTA tests and conventional susceptibility method (disc diffusion following EUCAST recommendations). For all phenotypes combined, the sensitivity, specificity, positive predictive value, and negative predictive value in the detection of 3GC resistance were, respectively (i) with BL-RED: 45.7, 100, 100, and 54.2% and (ii) with β-LACTA test: 52.2, 100, 100, and 56.9%. The positivity of tests allows to adapt antibiotic treatment whereas the negative result requires other tests. Moreover, these tests detect most Ambler class A-producing Enterobacterales (KPC, ESBL, extended-spectrum OXY) with sensitivities and specificities of 87.5 and 99% for BL-RED, respectively and both 100% for β-LACTA test (47/47 isolates). These two rapid tests failed to detect AmpC overexpressed (sensitivities of 2.7% for BL-RED and 0% for β-LACTA test) and Ambler class B-producing Enterobacterales (sensitivities of 40% for both tests) notably strains without ESBLs associated (sensitivities of 0% for both tests). BL-RED and β-LACTA tests are easy-to-use and mainly attractive when a positive result is obtained notably to detect most of the Ambler class A-producing Enterobacterales in <1 h after the positivity of the blood culture, allowing a rapid adaptation of the antibiotic therapy in patients.
由于快速确定感染多药耐药菌的患者至关重要，我们评估了两种可直接从阳性血培养物中在 1 小时内检测第三代头孢菌素（3GC）耐药肠杆菌科的快速诊断检测方法：BL-RED（电化学方法）和β-LACTA 测试（显色方法）。测试了一组 150 种具有耐药谱特征的临床菌株（例如青霉素酶、超广谱β-内酰胺酶（ESBLs）、头孢菌素酶过度产生、碳青霉烯酶、通透性）。将每个分离株的大约 100 CFU 混入无菌血培养瓶中，并在 BD BACTEC FX 自动化系统（Becton Dickinson，美国）中孵育。对阳性血培养物进行平行检测，使用 BL-RED 和β-LACTA 检测和常规药敏方法（根据 EUCAST 建议进行纸片扩散）。对于所有表型的组合，BL-RED 检测 3GC 耐药的灵敏度、特异性、阳性预测值和阴性预测值分别为（i）45.7%、100%、100%和 54.2%，（ii）β-LACTA 检测：52.2%、100%、100%和 56.9%。测试的阳性结果允许调整抗生素治疗，而阴性结果需要进行其他测试。此外，这些测试可检测大多数产 Ambler 类 A 的肠杆菌科（KPC、ESBL、广谱 OXY），BL-RED 的灵敏度和特异性分别为 87.5%和 99%，β-LACTA 测试均为 100%（47/47 株）。这两种快速检测方法未能检测到过度表达的 AmpC（BL-RED 的灵敏度为 2.7%，β-LACTA 检测的灵敏度为 0%）和产 Ambler 类 B 的肠杆菌科（两种检测方法的灵敏度均为 40%），特别是没有相关 ESBL 的菌株（两种检测方法的灵敏度均为 0%）。BL-RED 和β-LACTA 检测方法易于使用，主要在获得阳性结果时具有吸引力，特别是可以在血培养阳性后 1 小时内检测到大多数产 Ambler 类 A 的肠杆菌科，从而可以快速调整患者的抗生素治疗。
