Objective: To investigate the drug resistance, β-lactamase-encoding genes and protoporphyrin ferrochelatase-encoding genes of Ralstonia mannitolilytica, and to explore its structure and pathogenic function.
Methods: The strain was isolated by plate streaking method and identified by automatic bacteria detection system and 16S RNA gene PCR. Microdilution method was applied for drug susceptibility test. β-lactamases, extended spectrum β-lactamases (ESBL) and carbapenemases were detected using nitrocefin-disk, Kirby-Bauer disk, and Hodge test, respectively. Five β-lactamase-encoding genes and protoporphyrin ferrochelatase-encoding gene of the isolate were amplified by PCR for sequencing. Bioinformatic softwares were used to analyze the structure and function of the product of protoporphyrin ferrochelatase-encoding gene.
Results: A strain belonging to Ralstonia mannitolilytica was isolated. This isolate was sensitive to cefepime, ciprofloxacin, ofloxacin and tigecycline, but resistant to five penicillins, four cephalosporins and two carbapenems antibiotics. The isolate produced β-lactamases but did not produce ESBL and carbapenemases. The isolate had five distinct β-lactamase-encoding genes and protoporphyrin ferrochelatase-encoding gene. The product of protoporphyrin ferrochelatase-encoding gene contained two functional domains of protoporphyrin ferrochelatase belonging to type Ⅱ chelatase superfamily that presented the most closely genetic relationship with the protoporphyrin ferrochelatase of Neisseria meningidis.
Conclusions: The isolate of Ralstonia mannitolilytica has a higher resistance to β-lactam antibiotics and its β-lactamase-encoding genes are different with the common bacterial β-lactamase-encoding genes. Protoporphyrin ferrochelatase may act as an important virulence factor of Ralstonia mannitolilytica.
目的: 检测与分析解甘露醇罗尔斯顿菌的耐药性和β-内酰胺酶基因、原卟啉亚铁螯合酶基因及其结构和功能。
方法: 采用血平板分离划线培养、全自动细菌检测分析系统和16S RNA基因PCR分离并鉴定病原菌。采用微量稀释法对分离菌株进行药敏试验，β-内酰胺酶、超广谱β-内酰胺酶和碳青酶烯酶确证试验确定其产酶情况。采用PCR扩增分离菌株5个β-内酰胺酶基因和原卟啉亚铁螯合酶基因并测序。采用生物信息学软件分析该原卟啉亚铁螯合酶基因产物结构与功能。
结果: 患者血液中分离出解甘露醇罗尔斯顿菌。该菌株对头孢吡肟、环丙沙星、左氧氟沙星、替加环素敏感，但对五种青霉素类、四种头孢菌素类和两种碳青酶烯类抗菌药物耐药。该菌株产β-内酰胺酶但不产超广谱β-内酰胺酶和碳青酶烯酶。该菌株具有5个独特的β-内酰胺酶基因和原卟啉亚铁螯合酶基因，该基因产物为含2个Ⅱ类螯合酶超家族原卟啉亚铁螯合酶功能结构域，与脑膜炎奈瑟菌原卟啉亚铁螯合酶亲缘关系最近。
结论: 该株解甘露醇罗尔斯顿菌对β-内酰胺类抗菌药物有较高耐药性，其β-内酰胺酶基因与常见细菌β-内酰胺酶基因不同，原卟啉亚铁螯合酶可能是其重要毒力因子。