Resistance to imipenem in Pseudomonas aeruginosa

There was a slow increase in imipenem resistance in Pseudomonas aeruginosa at St. Thomas' Hospital in the 1990s, reaching 3% in 1994. Of the 94 imipenem-resistant strains, 69% were susceptible to all the other agents tested; 15% were also resistant to one other antibiotic, 5.3% to two, 6.4% to three, 4.3% to four or more compounds. 16% of strains were resistant to at least one other beta-lactam in addition to imipenem. Resistance to other antibiotics was more common among the strains for which imipenem MICs were 4 mg/L than among either imipenem-susceptible or imipenem-resistant (MICs greater than or equal to 8 mg/L) strains.