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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
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↗
PubMed1979

The response of Staphylococcus aureus to benzylpenicillin.

The response to benzylpenicillin of 2 strains of Staphylococcus aureus was investigated in vitro using 3 techniques in parallel: continuous turbidimetric monitoring, continuous microscopic monitoring, and thin-section electron microscopy. Cultures of staphylococci were exposed to several concentrations of penicillin for various intervals of time before terminating the antibiotic activity with penicillinase. Bacterial lysis by penicillin was concentration-dependent and showed an optimal dosage effect which was very marked for one of the strains. The growth and division of cells continued for up to 1 h in the presence of penicillin. A variety of morphological responses was observed at each penicillin concentration. These changes ranged from complete bacterial lysis to apparently normal cells, and included several different types of aberrant morphological forms. On addition of penicillinase to cultures exposed to penicillin, there was a time interval before survivors began to divide. This period was increased by raising the concentration of penicillin or by increasing the period of exposure to penicillin. Bacteria resuming growth after surviving penicillin action exhibited markedly aberrant septation. Most of the survivors were found to originate from clumps of cocci rather than from individual cells or small groups.

Dose-Response Relationship, Drug↗
PubMed1977

Is your dosage really necessary? Antibiotic dosage in urinary infection.

Dense cultures of bacteria were exposed to changing concentrations of beta-lactam antibiotics in an in-vitro model of the urinary bladder. The results suggest that uncomplicated urinary infection may respond to lower doses than are usually given without compromising the success of subsequent treatment in those cases in which such minimal treatment fails.

Anti-Infective Agents, Urinary↗
PubMed1977

The activity of polymyxins against Escherichia coli in an in-vitro model of the urinary bladder.

The activities against a strain of Escherichia coli of polymyxin B, colistin (polymyxin E) and their sulphomethyl derivatives sulphomyxin and colistin sulphomethate have been examined in an in-vitro model of the urinary bladder under conditions similar to those that may operate in the therapeutic situation. In the dynamic conditions of the model, polymyxins exhibited a reduced activity against E. coli in comparison with activity against exponentially growing cultures in a static system. Nevertheless, long-term suppression of bacterial growth was achieved with levels of polymyxin B and colistin that can be attained during therapy, whereas sulphomethylpolymyxins had little effect on bacterial growth even on prolonged exposure.

Bacteriolysis↗
PubMed1977

R plasmids from Asian strains of Vibrio cholerae.

Five R plasmids transferred from Asian strains of Vibrio cholerae all proved to be members of compatibility group C. A non-self-transmissible plasmid, stable in V. cholerae, was mobilized for transfer to Escherichia coli K-12 and found to be unstably inherited in that host. Plasmids of group C and P transferred to a wild V. cholerae strain were stably inherited.

Anti-Bacterial Agents↗