COMPARISON OF AGAR DILUTION, TUBE DILUTION, AND BROTH MICRODILUTION SUSCEPTIBILITY TESTS FOR DETERMINATION OF RAMOPLANIN MICS

Standard broth microdilution (with and without bovine serum albumin B SA supplementation), tube dilution, and agar dilution susceptibility tests were compared for determining ramoplanin MICs. With a data base of 246 clinical isolates of gram-positive bacteria from 33 U.S. sites, it was shown that (i) agar and tube dilution susceptibility tests gav e essentially the same results (93.9% of the test results were within 1 doubling dilution of equivalence), (ii) broth microdilution suscepti bility tests gave results up to 5 doubling dilutions higher than agar or tube assays, and (iii) this data skewing could be reversed by BSA s upplementation (final concentration, 0.02%) of the broth microdilution test medium.