Influence of inoculum growth phase on microdilution susceptibility tests

Two types of commercially available microdilution trays were inoculated with log-phase cultures, stationary-phase cultures, and direct suspensions of 18- to 24-h colonies, with essentially comparable results. Direct pick-up of colonies was also tested with two Prompt inoculation systems (3M Co.); they were found to be convenient and reliable methods for standardizing inocula without preincubation in broth and without turbidity adjustment.