The efflux pump inhibitor phenylalanine-arginine β-naphthylamide (PAβN) increases resistance to carbapenems in Chilean clinical isolates of KPC-producing Klebsiella pneumoniae

The presence of PAβN resulted in an increase in carbapenem MICs unrelated to efflux pump inhibition, and a decrease in the expression of ompK35 and ompK36 genes without an obvious difference in OMP profiles observed by SDS-PAGE. Therefore, additional factors are responsible for the increase in carbapenem MIC in the presence of PAβN.