THE species Escherichia coli is a large and heterogeneous group of organisms divided into types on the basis of their antigenic structure. There is some evidence that certain properties are found more commonly in strains isolated from disease processes than in those from normal faeces. These properties include haemolysin production, which has a high incidence in strains causing urinary-tract infections (Dudgeon, Wordley and Bawtree, 1921 ;Vahlne, 1945) ; necrotoxin production, which is associated with haemolysin production and is found in certain serotypes (Sjostedt, 1946); cytotoxicity in tissue culture, closely associated with the production of soluble haemolysin (Chaturvedi et al., 1969); production of large amounts of K antigen by strains infecting the kidney (Glyn, Brumfitt and Howard, 1971); and production of mucinase (ROSS, 1959) and of enterotoxin (Taylor, Maltby and Payne, 1958) by strains causing infantile gastroenteritis.Because of the evidence that carriage of E. coli round the external urethral meatus may be important in the pathogenesis of infection of the urinary tract (O'Grady et al., 1970), we have compared the properties of strains from this area which subsequently gave rise to infections of the urinary tract with strains which although colonising the urethral meatus did not give rise to infection. The association within strains of a number of different properties has also been studied. MATERIALS AND METHODSFifty strains of E. coli from urinary-tract infections, 397 strains from normal faeces and 30 strains obtained by swabbing the external urethral meatus (introital strains) were examined. Of the 30 introital strains, 15 subsequently gave rise to infections of the urinary tract in the patients from whom they were isolated. The patients from whom the remaining 15 strains were obtained either did not develop infections during the three months following the isolation of the strain or developed an infection due to a different strain. All these organisms were examined for the production of haemolysin and necrotoxin and serotypes were determined.To study the association in individual organisms of a number of different properties, 186 further strains of E. coli were examined. Fifty were from the faeces of ulcerative-colitis patients in remission, 50 from the faeces of ulcerative-colitis patients in relapse, 36 from the faeces of normal people and 50 from urinary-tract infections. These strains were not consecutive isolates but were chosen to include as far as possible equal numbers of haemolytic and

It is possible that pseudomonas in the bowel come from ingested food, but it is not known whether ingested pseudomonas will establish themselves in the bowel of normal people, what numbers if ingested will be detectable in the faeces and for how long they will remain in the bowel. The experiments described here were performed in an attempt to answer these questions. METHODS Volunteers. These were two men and one woman who were members of the laboratory staff. Their ages were between 29 and 35 and they had no known abnormality of the gastrointestinal tract. During the period of the investigation the volunteers ate no cold food at midday and all cold food and drinks taken at home were sampled for the presence of pseudomonas. On three occasions one of the volunteers had a 4-day course of oral ampicillin, 250 mg being taken 4 times a day, commencing 5 hr before the ingestion of the organisms. Strains. The doses of pseudomonas to be ingested were prepared from either laboratory strains or fresh isolates. The sources, the phage-types and serotypes of the seven strains used are shown in table I. Preparation of strains of pseudomonas for ingestion. The strains were grown in nutrient broth (Oxoid) at 37°C for 5 hr and then either this culture or dilutions of it were added to approximately 200 ml of milk containing 4 ml of aluminium hydroxide gel. The numbers of organisms ingested ranged from 5 x 102 to 2 x 108, determined from surface viable counts of the broth cultures on cetrimide-chloramphenicol plates. The organisms were ingested in the late afternoon approximately 4 hr after the last meal. Composition of the media used. Cetrimide broth: Oxoid nutrient broth no. 2 containing 0.2 mg cetrimide per ml. Cetrimide agar: Oxoid nutrient agar containing 0.3 mg cetrimide per ml. Cetrimide-chloramphenicol agar: as for cetrimide agar but with the addition of 2.5 ,ug chloramphenicol per ml. Examination of food. A few grammes of each type of cold food or cold drink eaten during a 24-hr period were pooled and emulsified. The mixture was used to inoculate a cetrimide agar plate and also a tube of cetrimide broth, which was subcultured to cetrimide agar after

Summary: Specimens of faeces were obtained at weekly intervals for one year from patients in a female medical ward and Escherichia coli present were typed. The faecal E. coli population of the patients was constantly changing. No serotypes of E. coli were dominant, but on 31 occasions during the year small clusters of patients carried the same type.

IF Escherichia coli organisms act directly as pathogens in the causation of ulcerative colitis, it is possible that evidence of their pathogenic role m a y be obtained by comparing the types of the organisms present in persons with and without this disease.It is now well established that certain strains of E. coli belonging to a small number of 0-groups may act as pathogens in the intestine in children. Of the strains in these serotypea, only a small number cause disease. T h m enteropathogenic strains give a positive dilatation reaction in ligated segments of the ileum in rabbits. The properties of strains of E. coli isolated from pathological material have been studied by Vahlne (1945), Ewertsen and Knipwhildt (1946) and Sjostedt (1946). These authors demonstrated that haemolysin production, necrotoxin production and toxicity for mice are generally found together in the same strains, and that strains with these properties belong to a small number of 0-groups and occur more commonly in peritonitis, appendicitis and urinary-tract infections than in normal faeces.The investigation reported in this paper is a comparison of the properties of strains of E. coli isolated from the faeces of patients with ulcerative colitis with those of strains isolated from patients with acute diarrhoea and persons without intestinal disease. MATERIAL AND METHODS Strains of E. coliOne specimen of faeces was obtained from each of 50 patients with ulcerative colitis. These specimens were cultured on MacConkey agar and on either blood agar or erythrocyte agar, and from the cultures of each specimen one lactosefermenting colony was selected and subcultured for examination. Forty-seven of the strains were identified as E. coli by tests of their biochemical reactions; these strains fermented glucose, lactose, dulcitol and mannitol with production of acid and gas, did not ferment adonitol and inositol, produced indole but not H2S, did not show gelatinase or urease activity, did not utilise citrate, were negative in the Voges-Proskauer test and positive in the methyl-red test. Strains of E. coli were obtained and identified in the same way from 49 persons without disease of the intestine and from 44 persons with acute diarrhoea.The patients with ulcerative colitis were hospital in-patients who were admitted because of an attack of the disease. Specimens of faeces were obtained within 4 days of admission, usually on the day of admission. Patients who were receiving * Present address:

SUMMARY Spirochaetes were isolated from rectal swabs of two homosexuals and the faeces of a third, using simple isolation techniques not previously applied to specimens of this type. The ease of culture of these organisms will enable their distribution and pathogenicity to be studied, particularly in relation to their significance in homosexuals.