Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Department of Clinical Microbiology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Department of Clinical Microbiology, Shanghai Center for Clinical Laboratory, Shanghai, China.
Infect Genet Evol. 2022 Aug;102:105301. doi: 10.1016/j.meegid.2022.105301. Epub 2022 May 11.
The Enterobacter cloacae complex is responsible for a variety of infections in hospitalized patients and is resistant to β-lactam antibiotics owing to the expression of AmpC β-lactamase. We report emerging resistance in Enterobacter roggenkampii exposed to ceftriaxone and explore the mechanism underlying mutations responsible for this resistance.
Three strains were derived from different samples from one patient (blood and liver abscess fluid). Antimicrobial susceptibility was evaluated by standard broth microdilution, while ampC expression was determined via RT-PCR. Genetic relatedness was evaluated via pulsed-field gel electrophoresis (PFGE). Species identification and comparative genome analysis were performed via genome sequencing. Mutation rate testing and selection of AmpC-derepressed mutants were conducted to explore the mutation mechanism.
E. roggenkampii F1247 was susceptible to third-generation cephalosporins (3GCs); F95 and F1057, found in blood sample on day 11 and liver abscess drainage fluid on day 25, were resistant. ampC expression was 341- and 642-fold higher in F95 and F1057, respectively, than in F1247. Three isolates were the same PFGE and sequence types (ST1778) and were highly homologous (2 and 4 core genome single nucleotide polymorphism differences). Compared to F1247, F95 possessed a 575 bp deletion, including 537 bp of ampD, whereas F1057 harbored only one amino acid mutation (Leu140Pro in ampD). The mutation rates from F1247 exposure to cefotaxime, ceftazidime, ceftriaxone, piperacillin-tazobactam, and cefepime were (1.90 ± 0.21) × 10, (3.18 ± 0.43) × 10, (2.00 ± 0.20) × 10, (2.92 ± 0.29) × 10, and zero, respectively. In vitro-selected mutations responsible for resistance were identified in ampD, ampR, and dacB.
E. roggenkampii may develop resistance in vivo and in vitro upon exposure to 3GCs and to a lesser extent to piperacillin-tazobactam. 3GCs should not be used as a monotherapy for E. roggenkampii infections. Therapy using cefepime or carbapenems may be preferred to piperacillin-tazobactam in the treatment of E. roggenkampii, especially if source control is difficult.
阴沟肠杆菌复合体可导致住院患者发生多种感染，且由于 AmpCβ-内酰胺酶的表达，其对β-内酰胺类抗生素具有耐药性。我们报告了在接触头孢曲松的罗格登肠杆菌中出现的新的耐药性，并探讨了导致这种耐药性的突变机制。
从一位患者的不同样本中（血液和肝脓肿液）获得了 3 株菌。通过标准肉汤微量稀释法评估抗菌药物敏感性，通过 RT-PCR 测定 ampC 表达。通过脉冲场凝胶电泳（PFGE）评估遗传相关性。通过全基因组测序进行种属鉴定和比较基因组分析。进行突变率测试和 AmpC 去阻遏突变体的选择，以探索突变机制。
E. roggenkampii F1247 对第三代头孢菌素（3GCs）敏感；F95 和 F1057 分别来自血液样本第 11 天和肝脓肿引流液第 25 天，均耐药。F95 和 F1057 的 ampC 表达量分别比 F1247 高 341 倍和 642 倍。3 个分离株的 PFGE 和序列类型（ST1778）相同，高度同源（2 个和 4 个核心基因组单核苷酸多态性差异）。与 F1247 相比，F95 缺失了 575bp，包括 537bp 的 ampD，而 F1057 仅携带一个氨基酸突变（ampD 中的亮氨酸 140 突变为脯氨酸）。F1247 暴露于头孢噻肟、头孢他啶、头孢曲松、哌拉西林-他唑巴坦和头孢吡肟的突变率分别为（1.90±0.21）×10、（3.18±0.43）×10、（2.00±0.20）×10、（2.92±0.29）×10 和 0。体外筛选出的耐药突变发生在 ampD、ampR 和 dacB。
E. roggenkampii 可能在体内和体外接触 3GCs 时，以及在较小程度上接触哌拉西林-他唑巴坦时产生耐药性。3GCs 不应作为治疗 E. roggenkampii 感染的单一药物。在治疗 E. roggenkampii 时，与哌拉西林-他唑巴坦相比，使用头孢吡肟或碳青霉烯类药物可能更优于哌拉西林-他唑巴坦，尤其是在难以控制感染源的情况下。
