Functional Characterization of a Novel Outer Membrane

Background: The diffusion of antibiotics through the outer membrane is primarily affected by the porin super family, changes contribute to antibiotic resistance. Recently we demonstrated that the CpxAR two-component signaling system alters the expression of an uncharacterized porin OmpCKP, to mediate antimicrobial resistance in K. pneumoniae. Principal Findings: In this study, functional characterization of the putative porin OmpCKP (denoted kpnO) with respect to antimicrobial susceptibility and virulence was evaluated by generating an isogenic mutant, DkpnO in a clinical isolate of K. pneumoniae. Estimation of uronic acid content confirmed that DkpnO produced,2.0 fold lesser capsular polysaccharide than the wild-type. The DkpnO displayed higher sensitivity to hyper osmotic and bile conditions. Disruption of kpnO increased the susceptibility of K. pneumoniae to oxidative and nitrostative stress by,1.6 fold and.7 fold respectively. The loss of the Klebsiella porin led to an increase in the minimum inhibitory concentration of tetracycline (3-fold), nalidixic acid (4-fold), tobramycin (4-fold), streptomycin (10-fold), and spectinomycin (10-fold), which could be restored following complementation. The single deletion of kpnO reduced the survival of the pathogen by 50 % when exposed to disinfectants. In Caenorhabditis elegans model, the kpnO mutant exhibited significantly (P,0.01) lower virulence. To dissect the role of PhoBR signaling system in regulating the expression of the kpnO, a phoBKP isogenic mutant was constructed. The phoBKP mutant exhibited impaired gastrointestinal stress response and decreased antimicrobial susceptibility. The mRNA levels o