Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA, United States.
Department of Pediatrics, University of California, Los Angeles, Los Angeles, CA, United States.
Front Cell Infect Microbiol. 2020 Oct 26;10:563482. doi: 10.3389/fcimb.2020.563482. eCollection 2020.
resides in a variety of aquatic environments. Infections with mainly occur after contact with fresh or brackish water. Nosocomial infections with can also occur. infections can be difficult to treat due to both intrinsic and acquired antimicrobial resistance (AMR) mechanisms. In 2018-19, we isolated multi-drug resistant (MDR) from two solid organ transplant patients with intra-abdominal infections. We aimed to characterize their AMR mechanisms and to determine their genetic relatedness to aid epidemiological investigation. We performed whole genome sequencing (WGS) using Illumina MiSeq and Nanopore MinIon on 3 isolates, with one isolate from Patient A (blood) and two isolates from Patient B (abdominal and T-tube fluid, isolated 2 weeks apart). Phenotypic assays included: Broth Microdilution (BMD), Modified Hodge Test (MHT), Modified Carbapenem Inactivation Method (mCIM), and EDTA Carbapenem Inactivation Method (eCIM). Data analyses were performed using CLCbio and Geneious. AMR genomic analysis revealed that all three isolates possess chromosomally encoded genes including (oxacillinase) (AmpC), and (metallo-beta-lactamase). All isolates tested strongly positive by MHT and mCIM, but only Patient B's second isolate (after 2 weeks of meropenem treatment) tested positive by eCIM. More intriguingly, Patient B's first isolate (before meropenem treatment) tested falsely susceptible to carbapenems by BMD, suggesting gene was not expressed constitutively. Phylogenetic analysis showed the two isolates from Patient B were highly similar with only 1 SNP difference. The isolate from Patient A only differed from Patient B's isolates by 35 and 36 SNPs, respectively, suggesting close genetic relatedness. Further epidemiological investigation is undergoing. We report the first cases of CphA-mediated carbapenem resistant in the U.S. It is concerning that 1 out of 3 isolates tested falsely susceptible to carbapenems by BMD despite clear carbapenemase production shown by strongly positive MHT and mCIM. In both cases, meropenem was initially used to treat the patients. Clinicians and microbiologists in the US should be aware of the emerging MDR nosocomial infections and the potential false carbapenem susceptible results due to CphA-type carbapenemase, which may be induced during treatment.
主要存在于多种水生环境中。感染主要发生在接触淡水或微咸水之后。也可能发生医院获得性感染。由于内在和获得性抗菌药物耐药性 (AMR) 机制，感染可能难以治疗。在 2018-19 年，我们从两名患有腹腔内感染的实体器官移植患者中分离出多药耐药 (MDR) 。我们旨在描述它们的 AMR 机制，并确定它们与遗传流行病学调查相关的遗传相关性。我们对 3 个分离株进行了 Illumina MiSeq 和 Nanopore MinIon 的全基因组测序 (WGS)，其中一个分离株来自患者 A（血液），两个分离株来自患者 B（腹部和 T 管液，相隔 2 周分离）。表型测定包括：肉汤微量稀释法 (BMD)、改良 Hodge 试验 (MHT)、改良碳青霉烯失活法 (mCIM) 和 EDTA 碳青霉烯失活法 (eCIM)。数据分析使用 CLCbio 和 Geneious 进行。AMR 基因组分析表明，所有三个分离株都具有染色体编码基因，包括 (oxacillinase) (AmpC) 和 (metallo-beta-lactamase)。所有分离株均通过 MHT 和 mCIM 检测呈强阳性，但仅患者 B 的第二个分离株（在 2 周美罗培南治疗后）通过 eCIM 检测呈阳性。更有趣的是，患者 B 的第一个分离株（在美罗培南治疗前）通过 BMD 对碳青霉烯类药物检测呈假敏感，表明 基因未被持续表达。系统发育分析显示，来自患者 B 的两个分离株高度相似，仅有 1 个 SNP 差异。来自患者 A 的分离株与患者 B 的分离株分别只有 35 和 36 个 SNP 差异，表明遗传关系密切。正在进行进一步的流行病学调查。我们报告了美国首例 CphA 介导的碳青霉烯类耐药 。令人担忧的是，尽管 MHT 和 mCIM 检测到的碳青霉烯酶产生强烈阳性，但 3 个分离株中有 1 个通过 BMD 检测对碳青霉烯类药物呈假敏感。在这两种情况下，最初都使用美罗培南治疗患者。美国的临床医生和微生物学家应该意识到新出现的多药耐药性 医院获得性感染以及由于 CphA 型碳青霉烯酶可能导致的潜在假碳青霉烯类药物敏感结果，这可能在治疗过程中诱导。
