Evaluation of direct disc diffusion susceptibility testing for bacteriuria using diluted urine against standard CDS method.

Consecutive urine specimens with > or = 10(9) organisms/L on microscopy were diluted 1:100 and direct disc diffusion susceptibility tests performed. Subsequently, the standard Calibrated Dichotomous Sensitivity (CDS) test was performed on all isolates. Urines with > 2 Isolates or where growth was < 10(8) colony forming units (CFU)/L were excluded. Only Gram negative organisms were considered. 361 urines were evaluated, 324 with one and 37 with 2 isolates, comprising 255 Escherichia coli, 49 klebsiella, 41 proteus, 29 either citrobacter, enterobacter, providencia, serratia or alcaligenes, and 14 Pseudomonas aeruginosa. There were 2272 organism/antimicrobial test comparisons. A concordance of 98.5% was obtained. The results are considered acceptable for routine clinical use.