Reduced porin expression with EnvZ-OmpR, PhoPQ, BaeSR two-component system down-regulation in carbapenem resistance of Klebsiella Pneumoniae based on proteomic analysis

Carbapenem-resistant Klebsiella pneumoniae (CRKP) has proven to be an urgent threat to human health. Proteomics (TMT/LC-MS/MS) and bioinformatics approaches were employed to explore the potential mechanisms underlying carbapenem resistance. Proteomic profiling of CRKP and susceptible KP (sKP) isolates revealed the involvement of outer membrane, beta-lactam resistance pathway, and two-component systems (TCSs) in carbapenem resistance. 27 CRKP strains and 27 susceptible Klebsiella pneumoniae strains were isolated from inpatients at the Second Xiangya Hospital, China to verify the mechanisms. Modified carbapenem inactivation method (mCIM) and PCR of common carbapenem resistance genes confirmed that 77.8% (21/27) of CRKP isolates were carbapenemase-producing. Porin decrease in CRKP isolates was found by SDS-PAGE and mRNA levels of major porins (OmpK35 and OmpK36). RT-qPCR detection of two-component systems (envZ, ompR, phoP, phoQ, baeS and baeR) revealed down-regulation of EnvZ-OmpR, PhoPQ, BaeSR TCSs. Expression of the TCSs, except ompR, were closely correlated with OMPs with the R-value >0.7. Together, this study reaffirmed the significance of the β-lactam resistance pathway in CRKP based on proteomic analysis. OmpK35/36 porin reduction and the controversial downregulation of EnvZ-OmpR, PhoPQ, and BaeSR TCSs were confirmed in carbapenem resistance of Klebsiella pneumoniae.