Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China.
Division of Infectious Diseases, State Key Laboratory of Biotherapy, Chengdu, China.
BMC Infect Dis. 2019 Apr 23;19(1):334. doi: 10.1186/s12879-019-3985-4.
Ralstonia picketti, Ralstonia mannitolilytica, and Ralstonia insidiosa have recently been regarded as emerging pathogens of infectious diseases, in particular as the pathogens responsible for nosocomial infection in immunocompromised patients. R. insidiosa differs from R. picketti and R. mannitolilytica, and its related infections are rarely reported.
Clinical data from two nosocomial bloodstream infection cases were extracted and analyzed. The causable isolates were identified by the VITEK 2 Compact system, matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and molecular identification methods using PCR with universal and species-specific primers. Antimicrobial susceptibility testing was performed using the broth microdilution method. Both of the isolates were subjected to whole genome sequencing using a HiSeq X10 Sequencer. Antimicrobial resistance genes, virulence factors, and plasmid replicons were identified from assembled genomes. A real-time RT-PCR experiment and a cloning experiment were conducted to explore the related class D β-lactamase-encoding genes.
Both patients recovered under therapy with antibiotics. Isolates were initially misidentified as R. mannitolilytica by the VITEK 2 Compact system rather than R. insidiosa, as identified by both MALDI-TOF MS and 16S rRNA gene sequencing. Both isolates were resistant to aminoglycosides, β-lactams, and polymyxin B. One isolate harboring bla was resistant to carbapenems. The whole genome sequencing data confirmed species identification based on average nucleotide identity (ANI) and revealed two variants of class D β-lactamase-encoding gene bla (bla and bla). The real-time RT-PCR experiment showed no difference in gene expression between bla and bla in our strains. The cloning experiment showed that variant OXA-573 had no carbapenem hydrolase activity.
We described two cases of nosocomial bloodstream infection caused by R. insidiosa strains. MALDI-TOF MS was cost-effective for rapid species identification. Clinicians should be aware that R. insidiosa can be resistant to commonly used antibiotics, even carbapenems.
拉氏不动杆菌、曼尼希不动杆菌和中间型拉氏不动杆菌最近被认为是传染病的新兴病原体，特别是免疫功能低下患者医院感染的病原体。与拉氏不动杆菌和曼尼希不动杆菌相比，中间型拉氏不动杆菌有所不同，其相关感染很少报道。
提取并分析了两例医院血流感染病例的临床数据。通过 VITEK 2 Compact 系统、基质辅助激光解吸电离飞行时间质谱（MALDI-TOF MS）和使用通用和种特异性引物的 PCR 分子鉴定方法鉴定了致病分离株。采用肉汤微量稀释法进行药敏试验。使用 HiSeq X10 测序仪对两种分离株进行全基因组测序。从组装基因组中鉴定了抗生素耐药基因、毒力因子和质粒复制子。进行了实时 RT-PCR 实验和克隆实验，以探索相关的 D 类β-内酰胺酶编码基因。
两名患者均在抗生素治疗下康复。两种分离株最初被 VITEK 2 Compact 系统误鉴定为曼尼希不动杆菌，而非 MALDI-TOF MS 和 16S rRNA 基因测序鉴定的中间型拉氏不动杆菌。两种分离株均对氨基糖苷类、β-内酰胺类和多粘菌素 B 耐药。一株携带 bla 的分离株对碳青霉烯类耐药。全基因组测序数据基于平均核苷酸同一性（ANI）确认了物种鉴定，并揭示了两种变体的 D 类β-内酰胺酶编码基因 bla（bla 和 bla）。实时 RT-PCR 实验表明，我们菌株中 bla 和 bla 的基因表达无差异。克隆实验表明，变体 OXA-573 没有碳青霉烯水解酶活性。
我们描述了两例由中间型拉氏不动杆菌菌株引起的医院血流感染病例。MALDI-TOF MS 是一种具有成本效益的快速种属鉴定方法。临床医生应注意，中间型拉氏不动杆菌可能对常用抗生素甚至碳青霉烯类药物耐药。
