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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.
Abstract:
Routine monitoring of antibiotic resistance at Children's Hospital, Boston, detected a dramatic increase in the prevalence of imipenem-resistant strains of Pseudomonas aeruginosa. Further studies documented that false resistance to imipenem was due, in part, to the loss of imipenem potency in customized MIC microdilution trays supplied by Sensititre Ltd. (West Sussex, United Kingdom). Recognition of the problem was delayed by use of the quality control standard recommended by the manufacturer, which were higher and broader than those suggested by the National Committee for Clinical Laboratory Standards.
Insights
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.