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Biomedical subjects

F O'Grady

Publications and source records attributed to F O'Grady.

At least 19 recordsLinked to original sources
PubMed1985

Comparative growth of Bacteroides species in various anaerobic culture media.

The growth of five species of Bacteroides in four anaerobic culture media was continuously monitored turbidimetrically. Interspecies differences were observed in the growth of Bacteroides spp. in the various media, but growth in Brain Heart Infusion broth supplemented with yeast extract, haemin and menadione, was consistently better than in Wilkins-Chalgren, Thioglycollate or Schaedler broths. Microscopy of cultures grown overnight in Brain Heart Infusion broth showed that the bacteria exhibited normal morphology but most species grown in the other media displayed filamentation or chain formation. Four of the five species grown in Schaedler broth also exhibited spheroplast formation. This morphological change occurred in the stationary phase of growth, was reduced by inclusion of NaCl in the medium and was abolished in Schaedler broth prepared at double the recommended strength.

Anaerobiosis↗
PubMed1983

Continuous opacity monitoring of the growth of bacteria under strict anaerobic conditions.

A newly designed instrument is described which generates continuous records of the opacities of six bacterial cultures growing under strict anaerobic conditions. Additions (for example, of antibacterial agents) or withdrawal of culture (for example, for viable counting) can be made at any time without breach of anaerobiosis. Use of the instrument is illustrated by growth curves obtained from small inocula of two strict anaerobes, Bacteroides asaccharolyticus and Peptostreptococcus anaerobius and by the effects on the growth curve of Bacteroides fragilis of adding various concentrations of metronidazole at different times.

Anaerobiosis↗
PubMed1983

Semiautomated determination of minimum bactericidal concentrations of antibiotics.

Using a newly devised 50-channel photometer which records the opacity of growing bacterial cultures, it was shown that the time taken by cultures diluted 1/1000 in fresh broth to reach 50% of the opacity of a fully grown culture was inversely related to the concentration of organisms in the original culture. This relation was used to determine the numbers of survivors after exposure to benzylpenicillin and gentamicin alone and in combination. The procedure is commended as a labour-saving and potentially rapid method of obtaining comprehensive information on the bactericidal action and interaction of antibiotics.

Dose-Response Relationship, Drug↗
PubMed1983

Therapeutic significance of nocardicin A stimulation of phagocyte function in experimental Pseudomonas aeruginosa infection.

Nocardicin A, a monocyclic beta-lactam antibiotic with modest anti-pseudomonal activity in vitro, controlled an otherwise fatal Pseudomonas infection in mice when given in doses which produced blood levels well below the minimum bactericidal concentration. In even smaller doses, it converted the partial protection afforded by modest doses of carbenicillin into full protection. Human polymorphonuclear leucocytes exposed to low concentrations of the drug in vitro and peritoneal macrophages recovered from mice treated with nocardicin A exhibited an unusually specific form of enhanced activity. Chemotaxis and phagocytosis were not affected, but intracellular killing of Ps. aeruginosa was significantly increased. This was shown to be due to an effect on the phagocyte and not to facilitated killing of organisms damaged by extracellular exposure to the antibiotic. It is argued that the effect on phagocyte function is sufficient to contribute materially to the therapeutic effect of nocardicin A.

Animals↗
PubMed1981

In-vitro activity of the novel oxa-beta-lactam antibiotic moxalactam (LY 127935) against dense populations of selected Gram-negative bacilli.

The activity of moxalactam, a new beta-lactam antibiotic with a novel molecular structure, was examined against dense populations of a variety of Gram-negative bacilli. The lytic activity of moxalactam against ampicillin-sensitive strains was similar to ampicillin, but the activity was maintained against ampicillin-resistant strains, including Pseudomonas aeruginosa, irrespective of whether the ampicillin resistance was 'intrinsic' (non-enzymic) or due to beta-lactamase. Of the 18 strains tested only one, a Hafnia sp., failed to respond to moxalactam.

Ampicillin↗
PubMed1980

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.

Antigens, Bacterial↗
PubMed1980

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.

Bacteria↗
PubMed1979

Emergence of trimethoprim-resistant enterobacteria in patients receiving long-term co-trimoxazole for the control of intractable urinary-tract infection.

In patients with previously intractable urinary-tract infection treated with low-dose co-trimoxazole for 6--58 (mean 32.7) months, the percentage of infected urines fell from 41.4 before treatment to 6.3 during treatment. Only 6 episodes of infection were due to trimethoprim-resistant bacteria. Results in a small group of patients in whom treatment was continued with trimethoprim alone were similar. Under the conditions of this study, long-term control of urinary-tract infection was not materially compromised by breakthrough infections due to trimethoprim-resistant organisms.

Bacteriuria↗
PubMed1979

An in vitro evaluation of clavulanic acid, a potent, broad-spectrum beta-lactamase inhibitor.

The in vitro efficacy of clavulanic acid, a new broad-spectrum inhibitor of enterobacterial beta-lactamases, was investigated. In conventional agar dilution tests, the presence of a sub-inhibitory level of clavulanic acid (8 microgram/ml) lowered the minimum inhibitory concentration of ampicillin for many resistant enterobacteria to therapeutically achievable levels. When tested against dense populations of Escherichia coli and klebsiella strains in a static turbidimetric system and in an in vitro model of the treatment of bacterial cystitis, clavulanic acid plus ampicillin suppressed bacterial growth for periods far exceeding the normal interdose interval at concentrations at which neither agent alone was effective. In addition to its activity as a beta-lactamase inhibitor, clavulanic acid may interact with other beta-lactam antibiotics in a second, distinct way. Because of this synergic interactions may occur with non-beta-lactamase producing organisms, and the overall synergic effect obtained with beta-lactamase producers may be compounded of two separate elements.

Ampicillin↗
PubMed1979

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.

Anti-Bacterial Agents↗