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False resistance to imipenem with a microdilution susceptibility testing system
E J O'Rourke1, K G Lambert, K C Parsonnet
1Division of Infectious Diseases, Children's Hospital, Boston, Massachusetts.
Journal of Clinical Microbiology
|April 1, 1991
Summary
False antibiotic resistance in Pseudomonas aeruginosa was linked to imipenem potency loss in specific microdilution trays. Using manufacturer-recommended quality controls delayed problem recognition, impacting patient care.
Area of Science:
- Clinical Microbiology
- Infectious Diseases
- Pharmaceutical Science
Background:
- Antibiotic resistance surveillance is crucial for effective patient treatment.
- Pseudomonas aeruginosa is an opportunistic pathogen frequently associated with hospital-acquired infections.
- Imipenem is a critical carbapenem antibiotic used to treat multidrug-resistant bacterial infections.
Purpose of the Study:
- To investigate a reported increase in imipenem-resistant Pseudomonas aeruginosa strains.
- To identify the underlying cause of false imipenem resistance.
- To evaluate the role of diagnostic materials in antimicrobial susceptibility testing.
Main Methods:
- Routine antibiotic resistance monitoring in a hospital setting.
- Microbiological studies to characterize bacterial resistance mechanisms.
- Assessment of antibiotic potency and stability in microdilution trays.
- Comparison of quality control standards from different regulatory bodies.
Main Results:
- A significant rise in imipenem-resistant Pseudomonas aeruginosa was observed.
- Loss of imipenem potency within customized Sensititre MIC microdilution trays was identified as a key factor.
- The use of manufacturer-recommended quality control standards, which differed from National Committee for Clinical Laboratory Standards guidelines, contributed to delayed detection.
Conclusions:
- Customized diagnostic materials can introduce errors in antimicrobial susceptibility testing.
- Adherence to standardized quality control protocols is essential for accurate resistance monitoring.
- Potential for false antibiotic resistance necessitates critical evaluation of laboratory methods and materials.