Evaluation of coagulase--mannitol test strips.

Abstract

Coagulase–mannitol paper strips for staphylococci combine tests for bound coagulase (read in 1 hr.) and mannitol oxidation (read in 6 hr.). Recent clinical isolates of Micrococcaceae were tested by slide and tube coagulase, tube mannitol, and strip coagulase and mannitol tests. All but one of the isolates of Micrococcus and Gaffkya were negative by the strip tests. In 188 isolates, the strip and slide coagulase tests agreed in only 87.2% of cases. Many (12.2%) isolates oxidized mannitol (strip positive) but did not ferment it (tube negative). The strip gave 13 false positive results and 15 false negative results. This amounts to only 6.9% and 7.9%, respectively, of all 188 isolates, but 14.3% of the positive reactions and 15.5% of the negative reactions were incorrect. The paper strip test does not appear to be sufficiently accurate for clinical use.