MATERIALS AND METHODS Organisms

THE isolation of enteric bacteria that do not conform to any of the recognised genera and species is common in clinical microbiology departments. The family Enterobacteriaceae consists of a continuous spectrum of closely related types and is difficult to subdivide. However, Edwards and Ewing (1962) showed that most cultures can be allotted to groups on the basis of similarity of biochemical properties. These groups constitute the currently accepted genera and species in the family. When a number of isolates from different sources give the same biochemical pattern and this does not fit any of the recognised groups there are two possible explanations. A single aberrant strain may have become locally prevalent as a result of cross-infection, or the isolates may represent a distinct but not generally recognised group of enterobacteria. This paper describes the investi-gation of such a group of organisms