Grading of coagulase-positive staphylococci in the control of hospital cross-infection

Abstract

The fermentation of mannitol by coagulase-positive staphylococci has been studied. It was found difficult to obtain reproducible results by methods which could be conveniently used in a routine department.A method of grading based on the fermentation of mannitol has been examined. Organisms of the supposedly most dangerous grade (Grade A) were isolated slightly more frequently from lesions than from carriers, but from all sources a high proportion of strains belonged to this grade.It was not possible to correlate the grades to which staphylococci were assigned with their production of diffusible antigens.In this hospital it seems that the proportion of strains assigned to Grade A has become very much higher than it was 15 years ago.We thank Prof. R. Knox, Mr J. B. Blaikley, Dr W. H. H. Merivale, and Dr R. H. Gorrill for the help and advice they have given us in the course of this investigation and numerous members of the nursing staff of Guy's Hospital for their co-operation in checking records and answering questions.