Comparison of Direct and Standardized Disk Diffusion Susceptibility Testing of Urine Cultures

Abstract

A comparison between direct and standardized disk diffusion tests was made on a total of 300 urine specimens containing ≥10 5 organisms/ml. Of these, 246 represented pure cultures and 54 represented mixed cultures. The number of major discrepancies per organism tested in pure culture was 18 (7.3%) and in mixed cultures it was 23 (42.6%). The percentage of major discrepancies per total number of antimicrobial drug comparisons made was 1.4%. Although this procedure may be of value in selected cases with pure cultures of organisms present in quantities ≥10 5 /ml, its use on a routine basis is not recommended.