Klebsiella pneumoniae Outer Membrane Porins OmpK35 and OmpK36 Play Roles in both Antimicrobial Resistance and Virulence

Abstract

OmpK35 and OmpK36 are the major outer membrane porins of Klebsiella pneumoniae . In this study, a virulent clinical isolate was selected to study the role of these two porins in antimicrobial resistance and virulence. The single deletion of ompK36 (Δ ompK36 ) resulted in MIC shifts of cefazolin, cephalothin, and cefoxitin from susceptible to resistant, while the single deletion of ompK35 (Δ ompK35 ) had no significant effect. A double deletion of ompK35 and ompK36 (Δ ompK35/36 ) further increased these MICs to high-level resistance and led to 8- and 16-fold increases in the MICs of meropenem and cefepime, respectively. In contrast to the routine testing medium, which is of high osmolarity, susceptibility tests using low-osmolarity medium showed that the Δ ompK35 mutation resulted in a significant (≥4-fold) increase in the MICs of cefazolin and ceftazidime, whereas a Δ ompK36 deletion conferred a significantly (4-fold) lower increase in the MIC of cefazolin. In the virulence assays, a significant ( P < 0.05) defect in the growth rate was found only in the Δ ompK35/36 mutant, indicating the effect on metabolic fitness. A significant ( P < 0.05) increase in susceptibility to neutrophil phagocytosis was observed in both Δ ompK36 and Δ ompK35/36 mutants. In a mouse peritonitis model, the Δ ompK35 mutant showed no change in virulence, and the Δ ompK36 mutant exhibited significantly ( P < 0.01) lower virulence, whereas the Δ ompK35/36 mutant presented the highest 50% lethal dose of these strains. In conclusion, porin deficiency in K. pneumoniae could increase antimicrobial resistance but decrease virulence at the same time.