Department of Clinical Laboratory, Toho University Omori Medical Center, Japan; Department of Microbiology and Infectious Disease, Toho University School of Medicine, Japan.
Department of Clinical Laboratory, Toho University Omori Medical Center, Japan; Department of Microbiology and Infectious Disease, Toho University School of Medicine, Japan.
J Microbiol Methods. 2021 Aug;187:106273. doi: 10.1016/j.mimet.2021.106273. Epub 2021 Jun 23.
Carbapenemase-producing Enterobacterales (CPE) have become a global health concern. Current molecular detection methods require special equipment and reagents. Thus, there is an urgent need for a highly sensitive, specific, and simple method for phenotypic detection of CPE in clinical microbiology laboratories. A simplified carbapenem inactivation method (sCIM) was recently reported. However, its utility for CPE detection has not been sufficiently evaluated to date. We evaluated the sCIM and compared it with the modified CIM (mCIM), using 133 CPE strains (producing IMP, 92; NDM, 11; NDM and OXA-48-like, 1; KPC, 13; OXA-48-like, 12; GES-24, 3; Nmc-A, 1) and 82 non-CPE strains (extended spectrum β-lactamase, 61; AmpC, 21). The sCIM was conducted by loading bacteria onto imipenem and meropenem disks. When imipenem disks with a 1+ bacterial load were used, the sensitivity and specificity of the sCIM were 97.0% and 100%, and those of the mCIM were 97.0% and 96.3%, respectively. The specificity of the sCIM decreased to 57.3% when the bacterial load on imipenem disks was increased to 2+. In contrast, when meropenem disks with a 1+ bacterial load were used, the sCIM had a lower sensitivity (78.2%) and an equivalent specificity (100%). When meropenem disks with a bacterial load of 2+ were used, the sensitivity and specificity of the sCIM increased to 96.2% and 93.9%, respectively. The diameter of the inhibition zone on meropenem disks was larger than that on imipenem disks, and the sCIM was less sensitive when meropenem disks were used. In addition, sCIM detection rates when using meropenem disks were particularly low for OXA-48-like producers (bacterial load 1+, 0/12; bacterial load 2+, 10/12). Our results indicate that the sensitivity and specificity of the sCIM was dependent on the bacterial load and that large bacterial loads led to false positives for AmpC and extended spectrum β-lactamase producers. Thus, the sCIM has high sensitivity and specificity for appropriate bacterial loads when imipenem disks are used.
产碳青霉烯酶肠杆菌科（CPE）已经成为全球关注的健康问题。目前的分子检测方法需要特殊的设备和试剂。因此，迫切需要一种在临床微生物学实验室中用于表型检测 CPE 的高度敏感、特异和简单的方法。最近报道了一种简化的碳青霉烯失活方法（sCIM）。然而，迄今为止，其用于 CPE 检测的实用性尚未得到充分评估。我们评估了 sCIM，并将其与改良 CIM（mCIM）进行了比较，使用了 133 株 CPE 菌株（产生 IMP，92 株；NDM，11 株；NDM 和 OXA-48 样，1 株；KPC，13 株；OXA-48 样，12 株；GES-24，3 株；Nmc-A，1 株）和 82 株非 CPE 菌株（扩展谱β-内酰胺酶，61 株；AmpC，21 株）。sCIM 通过将细菌加载到亚胺培南和美罗培南磁盘上进行。当使用载有 1+细菌负荷的亚胺培南磁盘时，sCIM 的灵敏度和特异性分别为 97.0%和 100%，mCIM 的灵敏度和特异性分别为 97.0%和 96.3%。当亚胺培南磁盘上的细菌负荷增加到 2+时，sCIM 的特异性降低至 57.3%。相比之下，当使用载有 1+细菌负荷的美罗培南磁盘时，sCIM 的灵敏度较低（78.2%），特异性相同（100%）。当使用载有 2+细菌负荷的美罗培南磁盘时，sCIM 的灵敏度和特异性分别提高至 96.2%和 93.9%。美罗培南磁盘上的抑菌环直径大于亚胺培南磁盘上的直径，并且当使用美罗培南磁盘时，sCIM 的灵敏度较低。此外，sCIM 检测 OXA-48 样产生菌的率特别低（细菌负荷 1+，0/12；细菌负荷 2+，10/12）。我们的结果表明，sCIM 的灵敏度和特异性取决于细菌负荷，并且较大的细菌负荷会导致 AmpC 和扩展谱β-内酰胺酶产生菌产生假阳性。因此，当使用亚胺培南磁盘时，sCIM 对于适当的细菌负荷具有较高的灵敏度和特异性。
