Laboratory evaluation of a multitest system for identification of gram-negative organisms

Seventy-two oxidase-positive or nonfermentative organisms, or both, all of which could be identified with reasonable certainty by alternative means, were used to challenge the OXI/FERM tube. There was 91% concurrence of identification between the two methods. Three observers, working independently, agreed upon the interpretation of each of the tests in the OXI/FERM system from 91% to 100% of the time. Duplicate OXI/FERM tubes inoculated with the same strain yielded identical interpretations 95% of the time for all tests except citrate utilization (89%). The OXI/FERM tube thus appeared to be an accurate identification method and yielded test results that were easily interpreted and adequately reproducible.