Division of Medical Microbiology, Johns Hopkins University School of Medicine, Meyer B1-193, 600 N. Wolfe Street, Baltimore, MD, USA.
Division of Pediatric Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Eur J Clin Microbiol Infect Dis. 2021 Nov;40(11):2315-2321. doi: 10.1007/s10096-021-04281-8. Epub 2021 Jun 11.
Detection of patients with intestinal colonization of carbapenem-resistant organisms (CRO), or more specifically carbapenemase-producing (CP) CRO, can prevent their transmission in healthcare facilities and aid with outbreak investigations. The objective of this work was to further develop and compare methods that combine selective culture and/or PCR to rapidly detect and recover CRO from fecal specimens. Molecularly characterized Gram-negative bacilli (n = 62) were used to spike fecal samples to establish limit of detection (LOD; n = 12), sensitivity (n = 28), and specificity (n= 21) for 3 methods to detect CP-CRO: direct MacConkey (MAC) plate and Xpert Carba-R (Cepheid) on growth, MAC broth and Carba-R testing of the broth, and direct testing by Carba-R. This was followed by a clinical study comparing methods in parallel for 286 fecal specimens. The LOD ranged from 1010 CFU/mL depending on the carbapenemase gene and method. Combined culture/PCR methods had a sensitivity of 100%, whereas direct Carba-R testing had a sensitivity of 96% for the detection of CP-CRO. All methods had specificities of 100%. The prevalence of CP-CRO (0.7%) and non-CP-CRO (5.2 %) were low in the clinical study, where all methods demonstrated 100% agreement. The three methods performed comparably in detecting CP-CRO. Direct Carba-R testing had a higher LOD than the combined selective culture methods, but this may be offset by its rapid turnaround time for detection of CP-CRO. The selective culture methods provide the benefit of simultaneously isolating CP-CRO in culture for follow-up testing and detecting non-CP-CRO.
检测肠道定植碳青霉烯类耐药菌（CRO）的患者，或更具体地说是产碳青霉烯酶（CP）CRO 的患者，可预防其在医疗机构中的传播，并有助于暴发调查。本工作的目的是进一步开发和比较结合选择性培养和/或 PCR 的方法，以便从粪便标本中快速检测和回收 CRO。使用分子特征明确的革兰氏阴性杆菌（n = 62）对粪便样本进行加标，以建立 3 种检测 CP-CRO 的方法的检测限（LOD；n = 12）、灵敏度（n = 28）和特异性（n= 21）：直接麦康凯（MAC）平板和 Xpert Carba-R（Cepheid）用于生长检测，MAC 肉汤和肉汤的 Carba-R 检测，以及直接 Carba-R 检测。随后，对 286 份粪便标本进行了比较平行的临床研究。LOD 取决于碳青霉烯酶基因和方法，范围从 1010 CFU/mL 不等。组合培养/PCR 方法的灵敏度为 100%，而直接 Carba-R 检测法检测 CP-CRO 的灵敏度为 96%。所有方法的特异性均为 100%。在临床研究中，CP-CRO（0.7%）和非 CP-CRO（5.2%）的患病率较低，所有方法均显示 100%的一致性。三种方法在检测 CP-CRO 方面表现相当。直接 Carba-R 检测法的 LOD 高于组合选择性培养方法，但这可能因检测 CP-CRO 的快速周转时间而得到弥补。选择性培养方法具有在培养物中同时分离 CP-CRO 进行后续检测和检测非 CP-CRO 的优势。
