The sources of Hospital infection of wounds with Clostridium welchii

The air of operating theatres ventilated by powerful extractor fans was sampled during operations with special media for Cl. welchii and Staph. aureus, and also for total organisms. Counts made with the slit-sampler showed the presence of Cl. welchii in all samples in a range slightly higher than that of Staph. aureus (mostly between five and twenty-five colonies per 100 cu.ft.). There was no evidence of a build-up of either Cl. welchii or Staph. aureus during the course of operations, nor were there any consistent peaks of contamination during operations.

Settle plates exposed on numerous days in the operating theatres showed similar counts of Cl. welchii and Staph. aureus—the latter slightly more abundant in this series. Settle-plate counts from many parts of the hospital and from the road outside provided evidence that airborne Cl. welchii comes into the hospital from outside, while Staph. aureus is contributed to the air inside the hospital. This view was supported by study with the slit-sampler and with settle plates in a dressing station ventilated with filtered air, where Cl. welchii was rarely found and Staph. aureus momentarily abundant during dressings; staphylococci but not Cl. welchii were dispersed by the operators in a mock operation. The numbers of airborne Cl. welchii inside and outside the hospital were higher in dry than in rainy weather.

Of the patients in the Burns Unit 35% had at some stage Cl. welchii in their burns; contamination was commoner in the more extensive burns. In contrast to Staph. aureus, Cl. welchii was usually present in small numbers and for a short period.

Cl. welchii was found in the burns of twenty out of thirty (66%) patients whose rectal swab taken on admission showed the presence of Cl. welchii; a significantly smaller proportion of patients whose rectal swabs were free from Cl. welchii picked up the organism while in hospital (eight out of thirty-two, 25%; x2 = 9.4, P < 0.01). This observation supports the view that burns and possibly other wounds acquire Cl. welchii by self-infection at least as often as from the environment. While it is obvious that plenum ventilation of operating theatres with filtered air is desirable, it is uncertain to what extent this will reduce the small hazard of post-operative gas gangrene.

We wish to thank Miss G. Hogg and Mr L. Hurst, F.I.M.L.T. for technical assistance, the surgeons and nursing staff of the Birmingham Accident Hospital for their co-operation, Mr N. R. Gill for photography, and Professors A. A. Miles and C. L. Oakley for kindly sending us strains of Cl. welchii.