In this study, we developed tigecycline resistance in Klebsiella pneumoniae ST23 strains in vitro and investigated the change in virulence associated with hypermucoviscosity. In vitro-induced tigecycline-resistant (TGC-IR) K. pneumoniae mutants were obtained from three tigecycline-susceptible (TGC-S) strains, belonging to ST23 and serotype K1, by culturing in media with tigecycline in a stepwise manner. An antimicrobial susceptibility test, string test, mucoviscosity assay, and capsular polysaccharide (CPS) quantification were performed. Biofilm formation and serum resistance were evaluated, and survival rates of bacterial strains in fruit flies and macrophages were measured. Alterations of rpsJ, ramR, soxR, acrR, and marR genes were investigated and the expression levels of ramA and efflux pump genes were evaluated. The hypermucoviscosity phenotype was dramatically decreased in the TGC-IR mutants. Reduced CPS production in TGC-IR mutants was also identified. Increased resistance to most other antimicrobial agents was found in TGC-IR mutants. In addition, the TGC-IR mutants exhibited reduced biofilm formation, low serum resistance, and decreased survival rates within fruit flies and macrophages. Our study shows that development of tigecycline resistance in hypervirulent K. pneumoniae strains result in defects in virulence associated with hypermucoviscosity.

中文翻译：

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高黏度肺炎克雷伯菌肺炎克雷伯菌序列类型23菌株对Tigecycline耐药性发展过程中黏液黏度的变化。

在这项研究中，我们在体外培养了肺炎克雷伯菌ST23菌株对替加环素的耐药性，并研究了与黏膜黏稠度增高相关的毒力变化。体外诱导的替加环素抗性（TGC-IR）肺炎克雷伯氏菌突变体是通过在带有tigecycline的培养基中分步培养的，从属于ST23和K1血清型的三个tigecycline易感性（TGC-S）菌株获得。进行了抗菌药敏试验，线试验，粘膜粘度测定和荚膜多糖（CPS）定量。评价生物膜形成和血清抗性，并测定果蝇和巨噬细胞中细菌菌株的存活率。的改变rpsJ，RAMR，soxR，的acrR和马尔研究了这些基因，并评估了ramA和外排泵基因的表达水平。在TGC-1R突变体中，高粘膜粘度表型显着降低。还确定了TGC-1R突变体中降低的CPS产生。在TGC-1R突变体中发现对大多数其他抗微生物剂的抗性增加。另外，TGC-1R突变体表现出减少的生物膜形成，低的血清抗性以及在果蝇和巨噬细胞内的存活率降低。我们的研究表明，高毒力肺炎克雷伯菌菌株中对替加环素的耐药性发展会导致与高黏黏度相关的毒力缺陷。