Mechanisms of resistance to fluoroquinolones and carbapenems in Pseudomonas putida.

OBJECTIVES Pseudomonas putida is an uncommon opportunistic pathogen, usually susceptible to antimicrobial agents. Data concerning resistance to antimicrobial agents in clinical P. putida isolates are limited. PATIENTS AND METHODS Susceptibilities to fluoroquinolones, carbapenems and other antibiotics were characterized in five clinical isolates of P. putida recovered from different patients with urinary tract infections as causative pathogens. Fluoroquinolone and carbapenem resistance were characterized genetically by the methods of PCR and DNA sequencing. Outer membrane protein (OMP) profiles were characterized by SDS-PAGE. RESULTS Four of five isolates were resistant or intermediate to both fluoroquinolones and carbapenems. Nucleotide sequences in the quinolone resistance-determining regions suggested that amino acid mutations such as Thr-83-->Ile in GyrA and Glu-469-->Asp in GyrB may contribute to high resistance to fluoroquinolones. Four metallo-beta-lactamase-producing isolates that showed resistance to carbapenems carried the IMP-type metallo-beta-lactamase genes. A combined effect of reduced production of 46 kDa OMP and metallo-beta-lactamase production was shown by a P. putida isolate exhibiting the highest MICs of carbapenems. CONCLUSIONS This study identified mechanisms of resistance to fluoroquinolones and carbapenems in clinical P. putida isolates.