1. An account is given of the design and conduct of a controlled trial of streptomycin by mouth in the treatment of infantile diarrhoea and vomiting.
2. The classification of cases is described. The streptomycin-treated and control series are shown to be comparable in respect of severity of illness on admission and in respect of other factors likely to affect progress.
3. The criteria adopted for assessment of progress are defined, viz. degree and duration of dehydration, duration of diarrhoea and tolerance of feeds.
4. Comparison of streptomycin-treated and control cases was based partly on progress during the first week of hospital stay and partly on subsequent progress.
5. No significant difference was shown between the streptomycin-treated and the control series in respect of progress during the first week. Severe relapses of diarrhoea were proportionately higher in the streptomycin-treated series, but the difference was not statistically significant.
6. The bacteriological investigations are described. Bact. coli O group 111 and Bact. coli O group 55 were used as ‘ indicator organisms’ in studying the immediate and delayed effects of streptomycin on the coliform flora of the intestine. The results show the inhibition, in streptomycin-treated cases, of coliform growth from the rectal swab, and the subsequent emergence of streptomycin-resistant strains.
7. Evidence of cross-infection with the ‘ indicator organisms’ is given. Problems of cross-infection and relapses of diarrhoea are discussed in relation to the assessment of the effects of a chemotherapeutic agent.
8. The difficulty of defining criteria for classification of cases and assessment of progress is discussed.
We wish to express our most grateful thanks to Sister A. Doherty and other members of the nursing staff of the hospital for their unfailing co-operation in a long and often tedious investigation; to members of the medical staff, in particular to Dr V. V. Tracey, for assisting in the work; and to the entire staff of the hospital's laboratory.
We are indebted to Prof. Robert Cruickshank for his help in initiating the trial and for his continued interest and encouragement; and to Dr Joyce Wright for valuable criticism and help in the bacteriological investigations. Acknowledgement is due to Dr R. Swyer, Physician (Infectious Diseases), St Ann's General Hospital, for facilities for carrying out the trial; to Dr Joan Taylor and Miss R. E. Hilton for their serological and biochemical investigations; and to Prof. A. Bradford Hill for helpful statistical criticism.