Microbiologic and clinical implications of bacteremia due to extended-spectrum-beta-lactamase-producing Klebsiella pneumoniae with or without plasmid-mediated AmpC beta-lactamase DHA-1.

Bacteremias caused by Klebsiella pneumoniae producing extended-spectrum beta-lactamase (ESBL-KP; n = 52) and producing both ESBL and AmpC-type DHA-1 beta-lactamase (ESBL-PMABL-KP; n = 20) were analyzed. Higher MIC(50)s and MIC(90)s for carbapenems, ciprofloxacin, and piperacillin-tazobactam were observed with ESBL-PMABL-KP than with ESBL-KP. Patients with oxyimino-β-lactam exposure and high modified Pitt bacteremia scores (HMPBSs) were at higher risk, while those with piperacillin-tazobactam and aminoglycoside exposure were at lower risk for ESBL-KP bacteremia. Patients with fluoroquinolone exposure, diabetes mellitus, and HMPBS were at higher risk, while those with aminoglycoside exposure were at lower risk, for ESBL-PMABL-KP bacteremia.