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Resistance to imipenem in Pseudomonas aeruginosa
A King1, K Shannon, I Phillips
1Department of Microbiology, UMDS, St. Thomas's Campus, London, UK.
Abstract:
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 > or = 8 mg/L) strains.
Insights
Imipenem resistance in Pseudomonas aeruginosa slowly rose in the 1990s. Most resistant strains remained susceptible to other antibiotics, but some showed co-resistance, particularly at lower imipenem minimum inhibitory concentrations.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen frequently associated with hospital-acquired infections.
- Carbapenem antibiotics, including imipenem, are critical for treating severe P. aeruginosa infections.
- Monitoring antimicrobial resistance patterns is essential for effective treatment strategies.
Purpose of the Study:
- To investigate the trend of imipenem resistance in Pseudomonas aeruginosa isolates.
- To characterize the susceptibility profiles of imipenem-resistant strains to other antimicrobial agents.
Main Methods:
- Retrospective analysis of Pseudomonas aeruginosa isolates from St. Thomas' Hospital during the 1990s.
- Determination of imipenem minimum inhibitory concentrations (MICs).
- Phenotypic susceptibility testing against a panel of other antimicrobial agents.
Main Results:
- A gradual increase in imipenem resistance was observed, reaching 3% by 1994.
- Of 94 imipenem-resistant strains, 69% remained susceptible to all other tested agents.
- Co-resistance to other antibiotics was noted in a subset of strains, more prevalent in those with imipenem MICs of 4 mg/L.
Conclusions:
- Imipenem resistance in P. aeruginosa showed a slow but steady increase during the 1990s.
- While many imipenem-resistant strains retained susceptibility to other drugs, a concerning proportion exhibited co-resistance.
- The association of co-resistance with specific imipenem MIC ranges warrants further investigation for clinical implications.