The Group I paracolon bacilli formed biochemically a stable group. They fermented glucose, maltose, mannite, and dulcite, but not saccharose. Most of them could be distinguished from Salmonella organisms by the late fermentation of lactose or the production of indole. Many resembled the Newcastle bacillus in being late-dulcite fermenters. Serologically 75% of the strains were identical, each containing the A antigen. Some formed a separate group containing the A antigen, andBact. alkalescensantigen and the C antigen of some Group III strains. The A strains are probably identical with those of Dudgeon & Pulvertaft (1927), but their strains were described as being motile. All Group I strains had minor agglutinins in common with the dysentery bacilli, particularly when freshly isolated. Most of Dudgeon's strains were isolated from cases of urinary infection, but in the present investigation almost all were isolated from the discharges of infants with diarrhoea and enteritis. This organism may be regarded as pathogenic or facultatively so, and deserves a name. I suggest it would be appropriate to attach to it the name of Dudgeon, who was the first to call attention to it.Biochemically Group III bacilli resembled Group I strains but differed in fermenting saccharose. Some were motile. The metabolic and biochemical properties examined were stable. Serologically many (40%) possessed the A antigen, but also possessed a type-specific antigen, E. Others (37%) possessed both C and D antigens, usually C but sometimes D was dominant. These strains are related to the dysentery bacilli by the possession of common, minor antigens. A group of serologically heterogeneous strains remained (23%), generally unrelated to the dysentery bacilli.Most Group II bacilli were stable biochemically, but some were not. Many strains of Group IV were unstable. Serologically, Groups II and IV were mostly heterogeneous, although 24% were included in the A, B, C, D, E pattern. Together they formed but a minority of all the paracolon bacilli.Further serological investigation is required to discover new antigens and to link up the paracolon bacilli isolated from various sources.This work was carried out under a whole-time grant from the Medical Research Council of Ireland to whom I am indebted.I wish to record my very best thanks to my director, Prof. R. A. Q. O'Meara, for his continuous interest and invaluable advice at all times and without whose aid this research would not have been possible. My gratitude and thanks are due to my colleague, Dr J. St L. O'Dea, for his unfailing co-operation, particularly in obtaining all the specimens so quickly, in assisting at the post-mortems, and for many other services too numerous to mention.Thanks are also due to the authorities, doctors and nurses of St Ultan's Hospital, Temple Street Hospital, St Kevin's Hospital, Clonskeagh Fever Hospital, Cork Street Hospital, and the Child Welfare Clinics in Dublin, particularly to Dr F. N. Elcock and Dr T. Murphy for their support and co-operation; to the ‘Diarrhoea and Enteritis’ Committee of the Department of Local Government and Public Health for their supervision of the research; and to the staff of the Department of Bacteriology, Trinity College, Dublin, where the research was carried out, for the help and facilities given.I would like to thank all those general practitioners in Dublin who co-operated by the early notification of cases and in other ways. Finally, I wish to record my appreciation to the Statistics Branch, Department of Industry and Commerce, for their interest and kindness in furnishing a valuable report.
GENETIC DIVERSITY OF LACTOBACILLI ISOLATED FROM HUMAN INFANT FECES*
