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Interaction of imipenem with erythromycin and tetracycline assessed by microdilution checkerboard techniques
Abstract:
Microdilution methodology was used to study the interaction of imipenem with erythromycin and tetracycline, a combination therapy that might be used for the treatment of serious pelvic inflammatory disease. The combination of imipenem and erythromycin showed no antagonism for Escherichia coli and Haemophilus influenzae but was antagonistic for Staphylococcus aureus, Enterococcus faecalis, and group B streptococci; the combination of imipenem and tetracycline was antagonistic for all strains except H. influenzae. Correlation between the results of kill curves and the measurement of fractional bactericidal concentration (FBC) indices was good, although FBC indices showed less antagonism than kill curves. Fractional inhibitory concentration indices showed poor correlation, rarely showing antagonism, and indeed showed synergy in three cases. If erythromycin or tetracycline is considered necessary in addition to imipenem in the treatment of pelvic inflammatory disease, it is probably more effective when given after the course of imipenem has been completed.
Insights
Investigating imipenem combined with erythromycin or tetracycline for pelvic inflammatory disease revealed antagonism in most bacteria. Sequential administration, with imipenem first, may be more effective for combination therapy.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Pelvic inflammatory disease (PID) requires effective antibiotic treatment.
- Combination therapy with imipenem, erythromycin, and tetracycline is a potential strategy for serious PID.
- Understanding drug interactions is crucial for optimizing PID treatment regimens.
Purpose of the Study:
- To evaluate the in vitro interaction between imipenem and erythromycin.
- To assess the in vitro interaction between imipenem and tetracycline.
- To determine the optimal administration sequence for combination antibiotic therapy in PID.
Main Methods:
- Microdilution methodology was employed to assess drug interactions.
- Kill curves and fractional bactericidal concentration (FBC) indices were utilized.
- Fractional inhibitory concentration (FIC) indices were also calculated.
Main Results:
- Imipenem-erythromycin combination showed antagonism against Staphylococcus aureus, Enterococcus faecalis, and group B streptococci.
- Imipenem-tetracycline combination demonstrated antagonism against most tested strains, except for Haemophilus influenzae.
- Kill curves and FBC indices showed good correlation, with FBC indices indicating less antagonism.
- FIC indices showed poor correlation and occasionally indicated synergy.
Conclusions:
- Imipenem-erythromycin and imipenem-tetracycline combinations exhibit significant antagonism against key pathogens in PID.
- Sequential administration, with imipenem followed by erythromycin or tetracycline, may be a more effective therapeutic approach.
- Further clinical studies are warranted to validate these findings in PID treatment.