F. O'Grady

Ammonia production by intestinal bacteria

Bacterial growth and the production of ammonia from urea and by deamination of peptone has been examined at various pHs in both conventional static bacterial cultures and in a continuous cultivation system. Growth occurred on primary testing of 93 out of 100 strains of aerobic Gram-negative bacteria at pH 5, and 48 out of 50 strains of Esch. coli at pH 4·6. Hydrolysis of urea by Proteus mirabilis decreased steadily from pH 7·2 to pH 5·3; below pH 5·3 little hydrolysis occurred. Ammonia production from peptones by Esch. coli decreased from pH 7·2 to pH 4·6. Considerable variation was noted in the ability of different strains to produce ammonia. Experiments with cultures containing both Esch. coli and Pr. mirabilis showed that more ammonia was produced at low pH than was produced by cultures of single organisms. At low pH reduction in the count of organisms was not found to be an essential prerequisite for reduction of ammonia formation.

Uropathogenic properties of Escherichia coli in recurrent urinary-tract infection.

Properties of Escherichia coli considered to be important in the pathogenesis of urinary-tract infection were investigated. The following properties were more common in E. coli strains isolated from urinary infections than in periurethral strains from healthy individuals: (i) O serogroups 2, 4, 6, 8, 18ab and 75; (ii) high K-antigen titre; (iii) production of haemolysin; (iv) production of fimbriae; (v) fermentation of salicin. The correlation between isolation of a strain from the urinary tract and possession of any single property was not strong; however, strains rich in a combination of these pathogenic properties were rarely isolated from the periurethral area of healthy subjects but were common in urinary infections. Nevertheless, a significant proportion of urinary strains had few pathogenic properties. Strains rich in pathogenic properties were more commonly isolated from upper urinary-tract infections than from lower-tract infections; this indicates that the properties of the invading organism may influence the localisation of infection.

RELATION BETWEEN RESIDUAL URINE VOLUME AND RESPONSE TO TREATMENT OF URINARY INFECTION

Abstract Residual urine volume (R.U.V.) has been measured using 131 I-hippuran in seventy-six women referred with a clinical diagnosis of urinary infection and correlated with the presence of bacteriuria and ease of treatment. Twenty-two of the patients remained abacteriuric for 3 months and of these only three had an increased R.U.V. (>1.0 ml.). The fifty-five women with bacteriuria had significantly increased R.U.V.S. Of the thirty who were easy to treat, sixteen had an increased R.U.V. while of the twenty-four who were difficult to treat all but two had an abnormal R.U.V. Patients over the age of 50 had significantly greater R.U.V.S than younger women, and proportionately more of them were difficult to treat. It is concluded that an increase in R.U.V. is associated with difficulty in treating urinary infection, and that R.U.V.S. of as little as 1–10 ml. are important in this regard.

Comparative in vitro activities of cefotaxime and ceftizoxime (FK749): new cephalosporins with exceptional potency.

Cefotaxime and its desacetoxymethyl derivative, ceftizoxime (previously known as FK749), are both extremely active against a wide spectrum of bacteria. In the present comparative study, the activity of ceftizoxime exceeded that of cefotaxime by a factor of four or more for strains of Klebsiella, Enterobacter, Providencia, Serratia, and Bacteroides; the only species for which the activity of cefotaxime exceeded that of ceftizoxime by a factor of four was Vibrio cholerae. Against other species, the activity of the two drugs was roughly comparable. Both showed outstanding activity against Haemophilus influenzae and Neisseria gonorrhoeae. Comparative turbidimetric and morphological studies revealed that ceftizoxime was able to induce spheroplast formation and rapid lysis in Escherichia coli strains at lower concentrations than cefotaxime. This difference was not found, however, when E. coli strains resistant to ampicillin by an intrinsic (nonenzymic) mechanism were tested.

Bacteriological Studies In Crohn'S Disease

Summary The bacterial flora of aspirates from the stomach, the upper jejunum, the mid-gut, and the terminal ileum of 13 patients with Crohns disease was compared with that obtained from similar sites in healthy subjects. The relationship of the bacterial flora to the site of disease and to the absorption of vitamin B12 and fat was examined. Increased colonisation of the upper gut was seen only in patients with obvious stasis due to upper-gut disease, or when the upper and lower gut were connected by a fistula. In patients with comparatively normal motility, or in whom disease was restricted to the terminal small bowel, the flora was similar to that of healthy subjects. Aerobic diphtheroids were virtually absent from and higher counts of yeasts were present in all areas of the gut of patients with Crohns disease. No consistent relationship could be demonstrated between absorptive defects and the presence of an abnormal bacterial flora. Malabsorption of vitamin B12 usually depended more on loss or disease of the terminal ileum than on increased numbers of bacteria in the small gut. Three patients who showed significant deconjugation of bile salts had steatorrhoea but bacterial overgrowth, including species able to deconjugate bile salts, was not always associated with increased excretion of fat.

The Effect of Lactulose on the Faecal Flora of Patients With Hepatic Encephalopathy

SUMMARY The changes that occurred in the faecal flora during the separate administration of lactulose and magnesium sulphate were studied in five patients with hepatic encephalopathy. Lactulose therapy produced significant increases in lactobacillus counts in three patients, and two of these patients showed clinical improvement. No systematic change occurred in the counts of other organisms during either treatment; in particular it was not possible to correlate clinical improvement with a reduction in the count of the two groups of organisms- enterobacteria and Bacteroides spp.-that are considered to be most active in the production of ammonia.

In Vitro Model Simulating the Form of Exposure of Bacteria to Antimicrobial Drugs Encountered in Infection

A new model, which is designed to investigate the in vitro activity of antibiotics as a function of different concentration-time curves, is described. The antibiotic is allowed to diffuse through a membrane into a bacterial culture until a peak level is reached; the antibiotic is then removed by flow-assisted back diffusion. With this arrangement it is possible to expose bacteria to a changing concentration of drug while maintaining a constant volume of bacterial culture. Preliminary studies were carried out to investigate the response of a strain of Escherichia coli to gentamicin. The results indicate that bacteria surviving exposure to concentrations of gentamicin similar to those obtained during therapy may exhibit an increase in resistance to the antibiotic. Images

Escherichia coli serotypes in urinary-tract infection in a medical ward.

Abstract A survey of Escherichia coli urinary-tract infection (U.T.I.) among patients admitted to a general medical female ward over a period of twenty-four months is described. The use of a full range of one hundred and forty-seven O-typing sera, together with K and H typing, has permitted a more complete identification and analysis than hitherto. Relatively few common O types were responsible for most of the infections. The O-type prevalence was similar in acute and chronic infection, but acute infections were invariably caused by a single organism whereas in chronic infections more than one E. coli serotype was simultaneously present in 12% of the patients, but there was no particular O-type prevalence. Patients with diabetes, malignant disorders, rheumatoid arthritis, and hypertension had a much higher incidence of E. coli U.T.I. than the rest of the ward population. Small epidemics of U.T.I. due to specific E. coli O types occurred in the ward: none was acquired by catheterisation or instrumentation. The evidence accords with an oral transmission of type-specific E. coli from the intestinal reservoirs of human carriers.

Bacterial infection and acute myeloblastic leukaemia: an analysis of two hundred patients undergoing intensive remission induction therapy.

A survey was undertaken to define the infectious problems which occurred during intensive treatment of acute myeloblastic leukaemia. Two-hundred patients, treated consecutively at a single hospital, were studied. Bacteraemia, pneumonia and wound infecions were the most common infectious problems; the most important bacterial pathogens were Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. The presence of severe neutropenia and/or falling granulocyte count were accompanied by a worse prognosis. Patients who had a temperature of at least 38°C at initial presentation had a significantly worse complete remission (CR) rate (P < 0.015) and survival rate (P < 0.01) than patients who were afebrile; this difference could not be explained by more frequent early death in the febrile group. Presence of fever at diagnosis, like age and platelet count, is thus an important prognostic factor. A scoring system, based on these diagnostic features, should help to identify those patients who, because of high probability of entering CR, should be aggressively treated. Conversely, the outlook for non-responding patients may be improved by the delivery of less intensive chemotherapy when probability of entering CR, based on criteria available within hours of admission, is very low.

Factors Governing the Emergence of Resistance to Nalidixic Acid in Treatment of Urinary Tract Infection

Cultures of Escherichia coli were exposed to nalidixic acid in an in vitro model in which the conditions of drug-organism interaction resembled those of bacterial cystitis treatment. Results obtained in this way suggested that emergence of bacterial resistance should not be a major problem in treatment of uncomplicated urinary infection; such cases might indeed respond to a less intensive course of treatment than is usual. More prolonged, high-dosage therapy with nalidixic acid may be required for patients with more complicated infections if the risk of failure from the emergence of bacterial resistance is to be minimized.