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Imipenem stability in a predried susceptibility panel
J S Daly1, B A Deluca, S R Hebert
1Department of Medicine, Medical Center of Central Massachusetts, Worcester 01605.
Abstract:
We performed a 15-month study using 11 clinical strains and 1 control strain (ATCC 27853) of Pseudomonas aeruginosa to determine whether changes in the manufacturing process of Sensititre predried panels result in a reliable test of susceptibility to imipenem. MIC and breakpoint susceptibility results remained stable during the manufacturer's recommended shelf life of 18 months and compared well with standard agar disk diffusion and broth macrodilution results. Imipenem concentrations measured by high-pressure liquid chromatography were acceptable through 15 months but declined in the breakpoint panels by approximately 50% at 18 months. Between 9 months and panel expiration, 13 of 141 (9%) of the MIC panel packages had moisture entry, as indicated by pink desiccants, with a resultant loss of imipenem activity of 32 to 100%. It appears that the new manufacturing process produces MIC panels that are reliable for imipenem susceptibility testing until the labeled expiration date, provided that packages containing pink desiccants are not used.
Insights
New manufacturing processes for Sensititre panels ensure reliable imipenem susceptibility testing. Avoid panels with moisture indicators, as these may compromise imipenem activity.
Area of Science:
- Clinical microbiology
- Pharmaceutical manufacturing
Background:
- The Sensititre system is widely used for antimicrobial susceptibility testing.
- Changes in manufacturing processes require validation to ensure test reliability.
Purpose of the Study:
- To evaluate the reliability of Sensititre predried panels manufactured with updated processes for imipenem susceptibility testing.
- To assess the impact of storage duration and package integrity on imipenem stability.
Main Methods:
- A 15-month study involving 11 clinical strains and 1 control strain of Pseudomonas aeruginosa.
- Comparison of results from Sensititre panels with standard agar disk diffusion and broth macrodilution methods.
- High-performance liquid chromatography (HPLC) was used to quantify imipenem concentrations.
Main Results:
- Minimum inhibitory concentration (MIC) and breakpoint susceptibility results remained stable up to 18 months.
- Imipenem concentrations were acceptable through 15 months but declined significantly by 18 months in breakpoint panels.
- Moisture entry into 9% of MIC panel packages resulted in a 32-100% loss of imipenem activity.
Conclusions:
- The updated manufacturing process yields reliable Sensititre MIC panels for imipenem susceptibility testing until the expiration date.
- Proper storage and avoidance of compromised packages (indicated by pink desiccants) are crucial for maintaining imipenem activity.