Emergence of Ceftazidime/Avibactam and Tigecycline Resistance in Carbapenem-Resistant Klebsiella pneumoniae Due to In-Host Microevolution.

Xinhong Han,Yunsong Yu,Dongdong Zhao,Xiaoting Hua,Jingjing Quan,Peng Lan,Qiucheng Shi,Yan Jiang,Yihan Mao,Ping Zhang,Xueqing Wu

doi:10.3389/fcimb.2021.757470

Abstract

Klebsiella pneumoniae can cause both hospital- and community-acquired clinical infections. Last-line antibiotics against carbapenem-resistant K. pneumoniae (CRKP), such as ceftazidime/avibactam (CZA) and tigecycline (TGC), remain limited as treatment choices. This study aimed to investigate the mechanisms by which CRKP acquires CZA and TGC resistance in vivo under β-lactam antibiotic and TGC exposure. Three CRKP strains (XDX16, XDX31 and XDX51) were consecutively isolated from an inpatient with a urinary tract infection in two months. PFGE and MLST showed that these strains were closely related and belonged to sequence type (ST) 4496, which is a novel ST closely related to ST11. Compared to XDX16 and XDX31, XDX51 developed CZA and TGC resistance. Sequencing showed that double copies of bla KPC-2 were located on a 108 kb IncFII plasmid, increasing bla KPC-2 expression in XDX51. In addition, ramR was interrupted by Insertion sequence (IS) Kpn14 in XDX51, with this strain exhibiting upregulation of ramA, acrA and acrB expression compared with XDX16 and XDX31. Furthermore, LPS analysis suggested that the O-antigen in XDX51 was defective due to ISKpn26 insertion in the rhamnosyl transferase gene wbbL, which slightly reduced TGC susceptibility. In brief, CZA resistance was caused mainly by bla KPC-2 duplication, and TGC resistance was caused by ramR inactivation with additional LPS changes due to IS element insertion in wbbL. Notably, CRKP developed TGC and CZA resistance within one month under TGC and β-lactam treatment without exposure to CZA. The CRKP clone ST4496 has the ability to evolve CZA and TGC resistance rapidly, posing a potential threat to inpatients during antibiotic treatment.

Highlights

Klebsiella pneumoniae, is a major pathogen that can cause both nosocomial- and community-acquired infections, such as urinary tract infections, bacteremia, respiratory infections and soft tissue infections, especially in immunocompromised individuals (Ullmann, 1998; Holt et al, 2015)
Significant differences in minimum inhibitory concentrations (MICs) were observed for CZA and TGC between XDX51 and the index strains
Three different genomic mutations were identified in XDX51, and all of them were caused by Insertion sequences

Summary

Introduction

Klebsiella pneumoniae, is a major pathogen that can cause both nosocomial- and community-acquired infections, such as urinary tract infections, bacteremia, respiratory infections and soft tissue infections, especially in immunocompromised individuals (Ullmann, 1998; Holt et al, 2015). The emergence of carbapenem-resistant K. pneumoniae (CRKP) has limited antibiotic therapeutic choices and led to serious challenges in clinical treatment and infection control (Rice, 2008; Livermore et al, 2015a; Moradigaravand et al, 2017). Ceftazidime/avibactam (CZA) and tigecycline (TGC) are last-line choices for the treatment of CRKP infections. A multicenter, observational study reported that CZA could be a reasonable substitute for colistin for the treatment of CRKP infections with reduced mortality (Van Duin et al, 2018). Resistance to CZA has been observed in strains with mutations in AmpC, blaKPC-2 and blaKPC-3, and the mutation point was mostly in W-loop in blaKPC genes (Shirley, 2018; Zhang et al, 2020). High expression of KPC-3 was reported to be associated with CZA resistance (Humphries and Hemarajata, 2017)

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