目的:吲哚金杆菌是一种临床相关的微生物,一直在上升,报道了多药耐药(MDR)菌株。已证明携带tet(X2)的吲哚基因对抗生素替加环素具有抗性,然而,对四环素家族的所有其他成员敏感。抗性的这种不一致性促使人们对tet(X2)对吲哚梭菌中替加环素抗性的贡献进行研究。材料和方法:在这项研究中,我们报告了对替加环素耐药但对四环素敏感的MDRC.indologies菌株(CI3125)中替加环素耐药的基因组机制的综合分析,多西环素,还有米诺环素.我们用全基因组测序,定量逆转录PCR,蛋白质印迹,抗生素降解试验,和外排泵抑制试验,以揭示吲哚梭菌对替加环素的耐药机制,并阐明四环素家族抗生素耐药机制的不一致。结果:我们的研究结果表明,CI3125携带60个抗生素抗性基因,分布在6个不同的遗传岛(GI)上,具有水平转移的潜力。值得注意的是,tet(X2)基因位于CI3125的GI06上。tet(X2)的遗传环境分析表明,黄杆菌属和拟杆菌属中的所有tet(X2)基因在上游共享一个保守且功能性的核糖体结合位点。与预期相反,我们的RT-qPCR显示,在CI3125中,tet(X2)未被转录,而Western印迹表明,在CI3125中,tet(X2)蛋白不存在。相反,我们证明,在存在五种不同的外排泵抑制剂[1-(1-萘基-甲基)-哌嗪,苯基-精氨酸-β-萘胺,维拉帕米,利血平,和羰基氰化物3-氯苯腙]。这一发现为外排泵参与替加环素耐药性提供了证据,这可能是C.indologenes之间的普遍机制。我们的研究表明,CI3125中对四环素家族的耐药性不一致可能归因于tet(X2)的沉默和替加环素外排泵的功能。结论:总体而言,我们的研究结果强调了基因组方法在理解临床相关微生物中抗生素耐药的潜在机制方面的重要性.当CI3125中的tet(X2)保持沉默时,我们的研究结果表明,它可能通过GI水平传播。因此,我们的研究结果对于在临床环境中处理吲哚梭菌感染具有重要意义.
Purpose: Chryseobacterium indologenes is a clinically relevant microorganism that has been on the rise, with multidrug-resistant (MDR) strains being reported. C. indologenes carrying tet(X2) has been demonstrated to be resistant to the antibiotic tigecycline, yet, sensitive to all other members of the tetracycline family. This inconsistency in resistance prompts an inquiry into the contribution of tet(X2) to tigecycline resistance in C. indologenes. Materials and Methods: In this
study, we report on a comprehensive analysis of the genomic mechanisms underlying tigecycline resistance in a MDR C. indologenes strain (CI3125) that was resistant to tigecycline but sensitive to tetracycline, doxycycline, and minocycline. We used whole-genome sequencing, quantitative reverse transcription PCR, Western blot, antibiotic-degrading tests, and efflux pump inhibiting tests to reveal the mechanism of tigecycline resistance in C. indologenes and elucidate the inconsistency in the antibiotic resistance mechanism for the tetracycline family. Results: Our findings demonstrate that CI3125 carries 60 antibiotic resistance genes distributed on 6 different genetic islands (GIs), with the potential for horizontal transfer. Notably, the tet(X2) gene is located on GI06 of CI3125. Genetic environment analysis of tet(X2) showed that all tet(X2) genes in Flavobacterium and Bacteroides share a conservative and functional ribosome-binding site upstream. Contrary to expectation, our RT-qPCR showed that tet(X2) was not transcribed in CI3125, and Western blot suggested the absence of tet(X2) protein in CI3125. Rather, we demonstrate that minimum inhibitory concentration values for tigecycline decreased two- to eight-folds in the presence of five different efflux pump inhibitors [1-(1-naphthyl- methyl)-piperazine, phenyl-arginine-β-naphthylamide, verapamil, reserpine, and carbonyl cyanide 3-chlorophenylhydrazone]. This finding provides evidence for the involvement of efflux pumps in tigecycline resistance, which is likely to be a universal mechanism among C. indologenes. Our
study proposes that the inconsistency in resistance to the tetracycline family in CI3125 may be ascribed to the silence of tet(X2) and the functions of efflux pumps for tigecycline. Conclusions: Overall, our results highlight the importance of genomic approaches in understanding the underlying mechanisms of antibiotic resistance in clinically relevant microorganisms. While tet(X2) in CI3125 is silent, our findings suggest that it may be horizontally spread through GIs. Hence, our findings have significant implications for the management of C. indologenes infections in clinical settings.