Characterization of Tigecycline-Heteroresistant Klebsiella pneumoniae Clinical Isolates From a Chinese Tertiary Care Teaching Hospital.

Qiaoyu Zhang,Yuhong Pan,Jiansen Chen,Liping Lin

doi:10.3389/fmicb.2021.671153

Qiaoyu Zhang, Yuhong Pan + Show 2 more

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https://doi.org/10.3389/fmicb.2021.671153

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Abstract

Tigecycline has been used as one of the therapeutic choices for the treatment of infections caused by multidrug-resistant Klebsiella pneumoniae. However, the emergence of tigecycline heteroresistance has led to great challenges in treating these infections. The purpose of this study was to investigate whether tigecycline-heteroresistant K. pneumoniae (TGCHR-Kp) exists in clinical isolates, and to further characterize the underlying molecular mechanisms involved in the development of tigecycline-resistant subpopulations. Of the 268 tigecycline-susceptible clinical K. pneumoniae isolates, 69 isolates were selected as tigecycline-heteroresistant candidates in the preliminary heteroresistant phenotypic selection by a modified disk diffusion method, and only 21 strains were confirmed as TGCHR-Kp by the population analysis profile (PAP). Pulsed-field gel electrophoresis (PFGE) analysis demonstrated that all the parental TGCHR-Kp isolates were clonally unrelated, and colonies confirmed as the heteroresistant subpopulation showed no significant differences from their respective parental TGCHR-Kp isolates. Efflux pump inhibitors reversed the tigecycline susceptibility in heteroresistant subpopulations. Mutations in the ramR and soxR genes lead to upregulation of the ramA and soxS transcriptional regulators, which in turn induced overexpression of the AcrAB-TolC efflux pump genes in TGCHR-Kps-resistant subpopulations. Moreover, mutations of rpsJ were also found in resistant subpopulations, which suggested that the rpsJ mutation may also lead to tigecycline resistance. Time-kill assays showed that the efficacy of tigecycline against TGCHR-Kps was weakened, whereas the number of resistant subpopulations was enriched by the presence of tigecycline. Our findings imply that the presence of TGCHR-Kps in clinical strains causes severe challenges for tigecycline therapy in clinical practice.

Highlights

Klebsiella pneumoniae (K. pneumoniae) is a critical nosocomial pathogen that can cause lower respiratory tract, urinary tract, lower biliary tract, and surgical wound site infections
Of the 334 clinical K. pneumoniae strains, 268 isolates were susceptible to tigecycline, which was detected by the automated broth microdilution (BMD) method
The overexpression of the AcrAB-TolC efflux pump and mutations of the rpsJ gene might contribute to the reduced susceptibility to tigecycline in the resistant subpopulations

Summary

Introduction

Klebsiella pneumoniae (K. pneumoniae) is a critical nosocomial pathogen that can cause lower respiratory tract, urinary tract, lower biliary tract, and surgical wound site infections. Tigecycline is one of the few remaining therapeutic options for treating infections caused by carbapenem-resistant or MDR Gram-negative bacilli. The prevalence of tigecycline-resistant K. pneumoniae is a cause for concern (Roy et al, 2013; Chiu et al, 2017). Expression of the acrAB genes is regulated by the local transcriptional repressor AcrR and the global transcriptional activators such as RamA, SoxS, and MarA (Schneiders et al, 2003; Bialek-Davenet et al, 2011; Rosenblum et al, 2011; Veleba et al, 2012; Wang et al, 2015; Blanco et al, 2016). SoxS induction depends on SoxR, and mutations within soxR can lead to its overexpression (Schneiders et al, 2003; Bialek-Davenet et al, 2011)

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