Identification of Salmonellae with the 4-methylumbelliferyl caprilate fluorescence test.

We have tested 750 Salmonella strains and 130 strains of other species of the family Enterbacteriaceae with the 4-methylumbelliferyl caprilate reagent (MUCAP) test. The MUCAP test is a fluorescence test for rapid identification of Salmonella strains. The non-Salmonella strains were strains sent for identification as suspected Salmonella strains and thus have phenotypes similar to those of Salmonella strains. All 748 tested Salmonella strains of subgroups I, II, III, and IV were positive in the MUCAP test. Of the two tested rare Salmonella subgroup V strains, one was positive and the other was negative. In the selected material containing strains with phenotypes similar to those of Salmonella strains, only one Hafnia alvei strain of 130 Enterbacteriaceae bacteria tested was positive. The fluorescence of the H. alvei strain, the six tested Salmonella dublin strains, and the positive Salmonella subgroup V strain was weaker than that of the other salmonellae. The MUCAP assay is simple and is performed within 5 min. With an almost 100% sensitivity for Salmonella strains, apart from a single Salmonella subgroup V strain, we found the MUCAP test to be a convenient complement to traditional biochemical identification methods, especially for atypical and unusual Salmonella strains.