Paunkov Ana, Hummel Karin, Strasser Doris, Sóki József, Leitsch David
Institute for Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Vienna, Austria.
VetCore Facility for Research, University of Veterinary Medicine, Vienna, Austria.
Front Microbiol. 2023 Mar 31;14:1158086. doi: 10.3389/fmicb.2023.1158086. eCollection 2023.
The anaerobic gut bacteria and opportunistic pathogen can cause life-threatening infections when leaving its niche and reaching body sites outside of the gut. The antimicrobial metronidazole is a mainstay in the treatment of anaerobic infections and also highly effective against spp. Although resistance rates have remained low in general, metronidazole resistance does occur in . and can favor fatal disease outcomes. Most metronidazole-resistant isolates harbor genes, commonly believed to encode for nitroreductases which deactivate metronidazole. Recent research, however, suggests that the mode of resistance mediated by Nim proteins might be more complex than anticipated because they affect the cellular metabolism, e.g., by increasing the activity of pyruvate:ferredoxin oxidoreductase (PFOR). Moreover, although genes confer only low-level metronidazole resistance to , high-level resistance can be much easier induced in the laboratory in the presence of a gene than without. Due to these observations, we hypothesized that genes might induce changes in the . proteome and performed comparative mass-spectrometric analyses with . 638R, either with or without the gene. Further, we compared protein expression profiles in both strains after induction of high-level metronidazole resistance. Interestingly, only few proteins were repeatedly found to be differentially expressed in strain 638R with the gene, one of them being the flavodiiron protein FprA, an enzyme involved in oxygen scavenging. After induction of metronidazole resistance, a far higher number of proteins were found to be differentially expressed in 638R without than in 638R with . In the former, factors for the import of hemin were strongly downregulated, indicating impaired iron import, whereas in the latter, the observed changes were not only less numerous but also less specific. Both resistant strains, however, displayed a reduced capability of scavenging oxygen. Susceptibility to metronidazole could be widely restored in resistant 638R without by supplementing growth media with ferrous iron sulfate, but not so in resistant 638R with the gene. Finally, based on the results of this study, we present a novel hypothetic model of metronidazole resistance and NimA function.
厌氧肠道细菌和机会致病菌离开其生态位并到达肠道外的身体部位时，可引发危及生命的感染。抗菌药物甲硝唑是治疗厌氧菌感染的主要药物，对某些菌也高度有效。虽然总体耐药率一直较低，但甲硝唑耐药在某些菌中确实会出现，并且可能导致致命的疾病结局。大多数耐甲硝唑的菌株携带nim基因，通常认为该基因编码使甲硝唑失活的硝基还原酶。然而，最近的研究表明，由Nim蛋白介导的耐药模式可能比预期的更复杂，因为它们会影响细胞代谢，例如通过增加丙酮酸：铁氧化还原蛋白氧化还原酶（PFOR）的活性。此外，虽然nim基因仅赋予某些菌低水平的甲硝唑耐药性，但在实验室中，与没有该基因相比，在有nim基因的情况下更容易诱导出高水平耐药性。基于这些观察结果，我们推测nim基因可能会诱导某些菌蛋白质组发生变化，并对有或没有nim基因的某些菌638R进行了比较质谱分析。此外，我们比较了两株菌在诱导出高水平甲硝唑耐药性后的蛋白质表达谱。有趣的是，在带有nim基因的638R菌株中，仅发现少数蛋白质反复出现差异表达，其中之一是黄素二铁蛋白FprA，一种参与清除氧气的酶。在诱导出甲硝唑耐药性后，与带有nim基因的638R相比，在没有nim基因的638R中发现有更多蛋白质差异表达。在前者中，血红素导入因子被强烈下调，表明铁导入受损，而在后者中，观察到的变化不仅数量较少，而且特异性也较低。然而，两株耐药菌株清除氧气的能力均有所降低。通过在生长培养基中补充硫酸亚铁，可使没有nim基因的耐药638R菌株对甲硝唑的敏感性广泛恢复，但对于带有nim基因的耐药638R菌株则不然。最后，基于本研究结果，我们提出了一种新的甲硝唑耐药和NimA功能的假设模型。
