First description of increased resistance in carbapenem-susceptible Klebsiella pneumoniae with imipenem treatment driven by outer membrane remodelling in China

The emergence of carbapenem-resistant Kelbsiella pneumoniae (CRKP) posed threats to human health. Although there are numerous studies regarding porin alteration in association with the production of ESBLs and/or AmpC β-lactamase, a systematic research about the treatment-emergence of porins alteration in antibiotic resistance does not exist yet. The aim of this study was to investigate the underlying mechanism and evolution of resistance of K. pneumoniae during carbapenem treatment. Here, we reported three strains (FK-2624, FK-2723 and FK-2820) isolated from one patient before and after imipenem treatment during hospitalization. Antibiotic susceptibility testing indicated that FK-2624 was susceptible to almost antimicrobials but fosfomycin; FK-2723 and FK-2820 were MDR. After imipenem therapy, FK-2820 was evolved to carbapenem-resistant. PCR and Whole-Genome sequencing ( WGS) indicated that resistance genes bla SHV , oqxA and fosA5 were detected in FK-2624, in addition, FK-2723 and FK-2820 harbored bla DHA , qnrB , aac (6’)-Ib . Virulence factors K57, ybtA, mrkD, entB and iroN were detected simultaneously in all of three strains. The results of pairwise comparisons , multi-locus sequencing typing (MLST) and pulsed-field gel electrophoresis (PFGE) revealed high homology among the isolates. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) results showed that isolate FK-2820 lacked OmpK 36 as there was a premature stop codon of the outer membrane porin encoding gene ompk36 confirmed by sequencing. Real-time RT-PCR revealed that the expression of ompK36 in FK-2820 was 0.093 times the control isolate ATCC 13883. Our study highlighted that the alteration of outer membrane porins due to the 14-day use of imipenem clinically play a potential role in leading to the carbapenems-resistance of FK-2820.