Biochemical investigation of Providence strains and their relationship to the Proteus group

1. Seventy-four urease negative and twelve urease weakly positive strains were studied which, according to their biochemical properties, had to be considered as belonging to the Providence group. Thirty Proteus rettgeri and five anaerogenic Proteus species were examined concomitantly. 2. 668 strains of Enterobacteriaceae were tested for the P.P.A. reaction, of which only the 192 Proteus and the 86 Providence strains rapidly transformed phenylalanine into phenylpyruvic acid. 3. P.P.A. test, IMViC reactions, fermentation properties, smell, swarming are similar to those of the Proteus group, particularly P. rettgeri; it is therefore suggested that the Providence strains should be incorporated in the Proteus group. 4. For all purposes the P.P.A. reaction appears to be better suited than the urea test for differentiating strains of Enterobacteriaceae from the Proteus-Providence group. The authors are grateful to Dr C. A. Stuart, Brown University, Providence, and Dr M. Greenstein, Sewage Disposal Works, Providence; to Dr W. H. Ewing, Communicable Disease Center, Chamblee, Georgia; to Prof. L. Olitzki, Hebrew University, Jerusalem; to Dr R. Mushin, University of Melbourne, Australia. We are especially indebted to Miss E. Salomon and Miss A. Engel for their valuable technical assistance.