Risk Factors for Acquisition of Fluoroquinolone or Aminoglycoside Resistance in Addition to Carbapenem Resistance in Pseudomonas Aeruginosa

BACKGROUND: Carbapenems, fluoroquinolones (FQs), and aminoglycosides (AGs) are key drugs for treating Pseudomonas aeruginosa infections, and accumulation of drug resistances make antibiotic therapy difficult. METHODS: We evaluated 169 patients with imipenem (IPM)-resistant P. aeruginosa and compared patient background and microbiological characteristics between groups with or without FQ resistance. Similar analyses were performed for AG. RESULTS: Of the 169 IPM-resistant strains, 39.1% showed resistance to FQs and 7.1% to AGs. The frequency of exposure to FQs within 90 days previously was higher in the group with FQ resistance (45.5%) than in the group without FQ resistance (13.6%). Similarly, 33.3% of patients in the group with AG resistance had been previously administered AGs, higher than the 7.6% of patients without AG resistance. Frequencies of metallo-β-lactamase (MBL) production were higher in the group with FQ or AG resistance (16.7% or 33.3%) than in the group without FQ or AG resistance (2.9% or 6.4%). Multivariate analyses showed exposures to FQs or AGs were related to the respective resistances. MBL production was a common factor for resistance to FQs or AGs, in addition to IPM-resistant P. aeruginosa. CONCLUSION: As well as promoting appropriate use of antibiotics, MBL production should be detected as a target of intervention for infection control.