Studies were made of a 14-room isolation ward in which the bedrooms were provided with individual ventilation units to provide a slight positive pressure within the rooms. Airborne staphylococci were detected with sedimentation plates.
The median count of Staphylococcus aureus in the occupied bedrooms was 4·6 col. per 14 cm. plate exposed for 24 hr. or 13 col./m.2 hr. When the air count was high virtually all the staphylococci proved to be of the phage type harboured by the patient in the room; with low counts a substantial proportion were apparently derived from patients in other rooms.
The apparent rate of acquisition of S. aureus in the nose of the patients was between 2·7 and 4·2 per 100 patient weeks at risk. This is substantially lower than has commonly been observed in open wards.
We are very graetful to Miss M. A. Adams, Sister in charge of the Almroth-Wright isolation Ward, and all her staff for all their help and co-operation during this study, which was supported by funds provided to St Mary's Hospital by the Ministry of Health for clinical research.
The reconstruction of the ward was designed by Mr A. Stableford, Group Engineer to St Mary's Hospital; the ventilation units were designed and supplied by White Bays and White Ltd., London.