Neuraminidase production by Bacteroidaceae.

The production of neuraminidase (EC 3.2.1.18) by 77 strains of Bacteroidaceae was investigated by techniques previously used to study neuraminidase production by clostridia. Conditions for culture and assay of Bacteroides fragilis neuraminidase were characterised. The enzyme is predominantly cell associated; it is not calcium dependent and the pH optimum for its production is c. 4.5. Most neuraminidase-positive Bacteroides strains produced the enzyme well in the test media but a few strains failed to produce it consistently in one or other of the media. Because of these occasional variations, strains were grown and tested in at least two media before being defined as neuraminidase negative. Within the B. fragilis group of species, B. fragilis, B. vulgatus, B. distasonis, B. ovatus, B. thetaiotaomicron and B. variabilis were neuraminidase positive while B. eggerthii, B. uniformis and B. splanchnicus were negative. Two subspecies of B. melaninogenicus (ss. melaninogenicus and ss. levii) were positive but the other (ss. intermedius) was negative. Strains of B. oralis and B. bivius produced the enzyme while B. ruminicola, B. disiens, B. asaccharolyticus and B. corrodens did not. The microaerophilic B. ochraceus were also positive. None of the Fusobacterium or Leptotrichia species tested produced neuraminidase. Our results for neuraminidase production are consistent for all strains of each species examined and we suggest that tests for neuraminidase production would be a valuable addition to biochemical tests currently used in taxonomic studies of the Bacteroidaceae.