Antibiotic resistance patterns in Pseudomonas aeruginosa: an 8-year surveillance study in a French hospital.

The susceptibility to ticarcillin, piperacillin, ceftazidime, aztreonam, tobramycin, amikacin, ciprofloxacin and fosfomycin of 3876 strains of Pseudomonas aeruginosa isolated during the period 1989-1996 in a French hospital was investigated. The most frequently active agents were amikacin and ceftazidime to which 13.3% and 16.1% of the isolates were resistant. Analysis of beta-lactam susceptibility patterns suggested that cephalosporinase derepression and intrinsic resistance were the predominant underlying mechanisms. There was a trend towards a decline in susceptibility to beta-lactams, aminoglycosides and ciprofloxacin over time. Multiresistance was frequent, mainly in O11 and O12 isolates.