Department of Microbiology, Faculty of Pharmacy, Misr International University (MIU), 19648, Cairo, Egypt.
Department of Microbiology & Immunology, Faculty of pharmacy-Girls, Al-Azhar University, 11651, Cairo, Egypt.
BMC Microbiol. 2022 Oct 14;22(1):248. doi: 10.1186/s12866-022-02660-5.
Carbapenemase-producing Gram-negative (CPGN) bacteria impose life-threatening infections with limited treatment options. Rigor and rapid detection of CPGN-associated infections is usually associated with proper treatment and better disease prognosis. Accordingly, this study aimed at evaluating the phenotypic methods versus genotypic methods used for the detection of such pathogens and determining their sensitivity/specificity values.
A total of 71 CPGN bacilli (30 Enterobacterales and 41 non-glucose-fermenting bacilli) were tested for the carbapenemase production by the major phenotypic approaches including, the modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), combined disk test by EDTA (CDT) and blue-carba test (BCT). The obtained results were statistically analyzed and correlated to the obtained resistant genotypes that were determined by using polymerase chain reactions (PCR) for the detection of the major carbapenemase-encoding genes covering the three classes (Class A, B, and D) of carbapenemases.
In comparison to PCR, the overall sensitivity/specificity values for detection of carbapenemase-producing organism were 65.62%/100% for MHT, 68.65%/100% for mCIM, 55.22%/100% for CDT and 89.55%/75% for BCT. The sensitivity/specificity values for carbapenemase-producing Enterobacterales were, 74%100% for MHT, 51.72%/ 100% for mCIM, 62.07%/100% for CDT and 82.75%/100% for BCT. The sensitivity/specificity values for carbapenemase-producing non-glucose fermenting bacilli were, 62.16%/100% for MHT, 81.57%/100% for mCIM, 50/100% for CDT and 94.74%/66.66% for BCT. Considering these findings, BCT possess a relatively high performance for the efficient and rapid detection of carbapenemase producing isolates. Statistical analysis showed significant association (p < 0.05) between bla and/or bla genotypes with MHT/CDT; bla/bla genotypes with CDT and bla genotype with BCT.
The current study provides an update on the performance of the phenotypic tests which are varied depending on the tested bacterial genera and the type of the carbapenemase. The overall sensitivity/specificity values for detection of CPO were 65.62%/100% for MHT, 68.65%/100% for mCIM, 55.22%/100% for CDT and 89.55%/75% for BCT. Based on its respective diagnostic efficiency and rapid turnaround time, BCT is more likely to be recommended in a resource-limited settings particularly, when molecular tests are not available.
产碳青霉烯酶的革兰氏阴性（CPGN）细菌引起危及生命的感染，治疗选择有限。严格快速检测 CPGN 相关感染通常与适当的治疗和更好的疾病预后有关。因此，本研究旨在评估用于检测此类病原体的表型方法与基因方法，并确定它们的灵敏度/特异性值。
对 71 株产碳青霉烯酶的 CPGN 杆菌（30 株肠杆菌科和 41 株非葡萄糖发酵杆菌）进行了主要表型方法的碳青霉烯酶产生检测，包括改良 Hodge 试验（MHT）、改良碳青霉烯酶灭活法（mCIM）、EDTA 联合纸片试验（CDT）和蓝卡巴试验（BCT）。对获得的结果进行了统计学分析，并与通过聚合酶链反应（PCR）获得的耐药基因型相关联，PCR 用于检测涵盖碳青霉烯酶 3 个类别（A 类、B 类和 D 类）的主要碳青霉烯酶编码基因。
与 PCR 相比，检测产碳青霉烯酶的微生物的总灵敏度/特异性值分别为 MHT 为 65.62%/100%、mCIM 为 68.65%/100%、CDT 为 55.22%/100%和 BCT 为 89.55%/75%。肠杆菌科产碳青霉烯酶的灵敏度/特异性值分别为 MHT 为 74%/100%、mCIM 为 51.72%/100%、CDT 为 62.07%/100%和 BCT 为 82.75%/100%。非葡萄糖发酵杆菌产碳青霉烯酶的灵敏度/特异性值分别为 MHT 为 62.16%/100%、mCIM 为 81.57%/100%、CDT 为 50%/100%和 BCT 为 94.74%/66.66%。考虑到这些发现，BCT 具有相对较高的性能，可有效快速检测产碳青霉烯酶的分离株。统计分析显示 MHT/CDT 与 bla 和/或 bla 基因型之间存在显著关联（p<0.05）；CDT 与 bla/bla 基因型之间存在显著关联；BCT 与 bla 基因型之间存在显著关联。
本研究提供了表型检测方法性能的最新信息，这些方法的性能因测试的细菌属和碳青霉烯酶的类型而异。检测 CPO 的总灵敏度/特异性值分别为 MHT 为 65.62%/100%、mCIM 为 68.65%/100%、CDT 为 55.22%/100%和 BCT 为 89.55%/75%。基于其各自的诊断效率和快速周转时间，BCT 更有可能在资源有限的环境中得到推荐，特别是在无法进行分子检测时。
