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Dirithromycin disc susceptibility tests: interpretative criteria and quality control parameters.

A L Barry·M A Pfaller·P C Fuchs
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Abstract

Dirithromycin and its bioactive metabolite (erythromycylamine) were compared in vitro to erythromycin against 450 bacterial isolates. Dirithromycin and erythromycylamine did not differ in their in-vitro activity and the two compounds were additive when combined in equal proportions. Both compounds were active against erythromycin-susceptible bacteria but erythromycin was two to four times more potent on a weight-to-weight basis. Interpretive criteria for dirithromycin were not based on achievable blood concentrations since tissue concentrations may be 20-30 times greater than peak serum levels. Dirithromycin-susceptible strains were those with zones > or = 19 mm in diameter (15 micrograms dirithromycin disc) or MIC < or = 2.0 mg/L and resistance was defined as a zone < or = 15 mm or MIC > or = 8.0 mg/L. Interpretive criteria for testing Haemophilus influenzae on Haemophilus Test Medium (HTM) agar were not defined because of the drug's poor activity in the test system used. Two multi-laboratory studies were also undertaken, one to define quality control limits for disc diffusion tests and the other to define broth microdilution MIC control limits for tests with dirithromycin.

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Anti-Bacterial AgentsBacteriaDrug Evaluation, PreclinicalEnterococcus faecalisErythromycinHaemophilus influenzaeMacrolidesMicrobial Sensitivity TestsQuality ControlStaphylococcus aureusJournal ArticleResearch Support, Non-U.S. Gov't

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A L Barry, M A Pfaller, P C Fuchs. 1993. Dirithromycin disc susceptibility tests: interpretative criteria and quality control parameters.. https://doi.org/10.1093/jac%2F31.suppl_c.27

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