Detection of Sialidase ( Neuraminidase ) Activity in Actinomyces Species by Using 2 ' - ( 4 - Methylumbelliferyl ) o 1 - D - N - Acetylneuraminic Acid in a Filter Paper Spot Test BERNARD

was developed by using 2'-(4-methylumbelliferyl)oa-D-N-acetylneuraminic acid as substrate in a filter paper spot test. The method was compared to conventional assays that use 2'-(4-methylumbelliferyl)ax-D-N-acetylneuraminic acid and bovine submaxillary mucin and was found to be in excellent agreement. Organisms with >10 U of enzyme activity (in nanomoles per minute per milligram of cell protein) gave positive reactions, while those with 2.7 to 9.0 U gave only weak reactions. Isolates with <2.7 U of activity were detected upon prolonged incubation. Sialidase activity was detected in 79% of 71 clinical isolates representing five species of Actinomyces. The percentage of sialidase-producing isolates of each species varied considerably: Actinomyces israelii, 63%; A. meyeri, 73%; A. naeslundii, 85%; A. odontolyticus, 73%; and A. viscosus, 100%.