Usefulness of Commercially Available Media to MIC-Determinations of Trimethoprim
Since trimethoprim and cotrimoxazole came into use several authors have pointed out the presence of antagonists to TMP in most commercially prepared media. In 1971 Koch and Burchall showed that thymidine was the most important TMP-antagonist in those media. Amyes and Smith (1974) recently compared several media, among others Oxoid Diagnostic Sensitivity Test Agar and Wellcotest Agar; they observed that DST supported the growth of thymineless mutants; the suggestion that this medium contained thymine and/or thymidine was confirmed by sensitivity-testing indicating that DST was unsatisfactory for IMP-sensitivity-testing; they also showed that Wellcotest Agar contains a uridinelike compound and that this prevents the utilisation of thymine (not of thymidine) by thymineless mutants.
KeywordsMinimal Inhibitory Concentration Open Circle Sensitivity Testing Complete Inhibition Dilution Method
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