Objective: This study aimed to analyze the homology between carbapenem-resistant organisms (CRO) intestinal colonization strains and bloodstream infection (BSI) strains in patients undergoing hematopoietic stem cell transplantation (HSCT), confirming the clinical use of the real-time rectal swab Xpert Carba-R assay, and investigate its feasibility in early warning of BSI. Methods: Drug-resistant strains obtained from rectal swabs and blood culture samples of patients undergoing the same HSCT from January 2021 to December 2021 were collected and analyzed. The homology of the CRO intestinal colonization and BSI strains was confirmed using strain identification, antimicrobial resistance phenotyping, whole genome sequencing (WGS), multilocus sequence typing (MLST), and carbapenemase type identification. Rectal swab cultures and the real-time rectal swab Xpert Carba-R assay were conducted concurrently on patients with HSCT from August 2021 to August 2022. The accuracy of the real-time rectal swab Xpert Carba-R assay was confirmed with the sequencing results of polymerase chain reaction amplification products of the carbapenemase gene from purified colonies as a reference standard. Results: This study included 24 CRO strains from 10 patients undergoing HSCT, including 14 intestinal colonizers and 10 CRO-BSI strains. The results revealed that the CRO intestinal colonization strains and CRO-BSI strains from the same patient and their carbapenemase genes were almost identical. Additionally, WGS revealed that CRO intestinal colonization and CRO-BSI strains from the same patient were more closely related than strains from different patients. Additionally, this study included 488 rectal swab specimens from 184 patients undergoing HSCT, with CRO detection rates of 16.4% for rectal swab culture and 18.4% for the real-time rectal swab Xpert Carba-R assay. The overall sensitivity, specificity, and positive and negative predictive values of the real-time rectal swab Xpert Carba-R assay were 96.6%, 72.8%, 90.6%, and 88.9%, respectively. Conclusions: A high degree of homology was found between the CRO intestinal colonization strains and the CRO-BSI strains in patients undergoing HSCT. The real-time rectal swab Xpert Carba-R assay is a reliable and convenient method for detecting common carbapenemase genes, serving as an alternative to rectal swab culture for early warning of CRO-BSI.
目的： 分析造血干细胞移植（HSCT）患者耐碳青霉烯类革兰阴性菌（CRO）肠道定植菌株与血流感染（BSI）菌株的同源性，验证实时肛拭子Xpert Carba-R检测在临床应用中的价值，探讨其预警BSI的可行性。 方法： 收集并分析2021年1月至2021年12月从HSCT患者的肛拭子和血培养样本中获得的耐药菌株，使用菌种鉴定、抗菌药物耐药表型、全基因组测序（WGS）、多位点序列分型和碳青霉烯酶型鉴别等方法，验证CRO肠道定植和BSI菌株的同源性。对2021年8月至2022年8月的HSCT患者同时进行肛拭子培养和实时肛拭子Xpert Cabar-R酶型筛查，以纯化菌落碳青霉烯酶基因多重实时聚合酶链反应（PCR）扩增产物的测序结果为参照标准，验证实时肛拭子Xpert Cabar-R检测的准确性。 结果： 本研究共纳入10例HSCT患者的24株CRO菌株，其中肠道定植菌14株，BSI菌10株。同一患者的CRO肠道定植和BSI菌株及其碳青霉烯酶基因高度一致，WGS显示同一患者的CRO肠道定植菌和BSI菌的亲缘关系比不同患者的菌株关系更密切。此外，本研究纳入184例HSCT患者的488份肛拭子标本，肛拭子培养和实时肛拭子Xpert Cabar-R的CRO检出率分别为16.4%和18.4%，实时肛拭子Xpert Carba-R检测的总体敏感性、特异性、阳性预测值和阴性预测值分别为96.6%、72.8%、90.6%和88.9%。 结论： HSCT患者CRO肠道定植菌株与BSI菌株具有高度同源性，实时肛拭子Xpert Carba-R是检测常见碳青霉烯酶基因可靠且方便的方法，可替代肛拭子培养预警CRO-BSI的发生。.
Keywords: Bloodstream infection; Carbapenem-resistant organism; Colonization; Hematopoietic stem cell transplantation; Intestinal microbiota; Xpert Carba-R.