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Biomedical subjects

M A Daw

Publications and source records attributed to M A Daw.

6 recordsLinked to original sources
PubMed1996

Bacteriocins: nature, function and structure.

Bacteriocins are extracellular substances produced by different types of bacteria, including both Gram positive and Gram negative species. They can be produced spontaneously or induced by certain chemicals such as mitomycin C. They are biologically one of the important substances, and have been found to be useful in membrane studies and also in typing pathogenic microorganisms causing serious nosocomial infections. Bacteriocins are a heterogeneous group of particles with different morphological and biochemical entities. They range from a simple protein to a high molecular weight complex: the active moiety of each molecule in all cases seems to be protein in nature. The genetic determinants of most of the bacteriocins are located on the plasmids, apart from few which are chromosomally encoded. These bactericidal particles are species specific. They exert their lethal activity through adsorption to specific receptors located on the external surface of sensitive bacteria, followed by metabolic, biological and morphological changes resulting in the killing of such bacteria. This review summarises the classification, biochemical nature, morphology and mode of action of bacteriocins as well as their genetic determinants and the microbiological relevance of these bactericidal agents.

Bacteria↗
PubMed1993

Prevalence of metronidazole-resistant Helicobacter pylori in dyspeptic patients.

Susceptibility to metronidazole of 213 clinical strains of H. pylori from dyspeptic patients was determined by a plate dilution method. Seventy two (33.8%) of the strains were resistant to metronidazole (MIC > 8 mg/L), 20 of these were from 24 patients who had received previously metronidazole (83.3%), giving a primary (pretreatment) resistance rate of 27.5% (52/189). The resistance rate was higher in women than in men, especially aged 50 to 59 years old (43.6% vs 23.3%, p < 0.001). The resistance rate was lower in patients at 60 or over (9.8%), but similar between the younger patients groups (38.8% - 49.0%). There was no difference in the resistance rate between peptic ulcer disease (32.6%) and nonulcer dyspepsia (34.7%). These data indicated that metronidazole resistance in H. pylori is absolutely associated with previous use of the drug, and the higher resistance rate in women may be due to the more frequent prescription of the drug for their gynaecological infection or operation. Therefore, testing of susceptibility of H. pylori to metronidazole is important. A new susceptibility testing technique, the E-test was evaluated in this study and found to give comparable results to the plate dilution method and also had the advantage of being simple to perform.

Adolescent↗
PubMed1992

Application and assessment of cloacin typing of Enterobacter cloacae.

Three methods, O-serotyping, phage typing and susceptibility to bacteriocins, were used to type 357 clinical isolates of Enterobacter cloacae cultured from 219 patients. One hundred and sixty isolates were typed by serology and phage typing. When these two methods were used, primary classification of isolates was based on serology (65.7% typable) and phage typing for further subdivision (94.1% typable). When all the isolates were typed by cloacin susceptibility, 81.5% of them were typable. Maximum discrimination between cultures was achieved when the three methods were used together; no single method was sufficiently discriminatory. There was a close parallel between serotyping and bacteriocin lysis pattern. The latter was easy to perform and the results were achieved within 48 h. By applying this typing system two episodes of cross-infection were identified in a haematology/oncology unit and intensive care unit.

Bacteriophage Typing↗
PubMed1991

Short report: the effect of omeprazole on Helicobacter pylori and associated gastritis.

Twenty-one patients with endoscopically confirmed duodenal ulceration, who had failed to heal with an H2-antagonist, were given omeprazole 20 mg o.m. for four weeks. Four antral biopsies from each patient were taken at endoscopy before, at the end of, and four weeks after treatment. Rapid urease test, culture, histopathology and transmission electron microscopy were carried out on these biopsies to determine the presence of Helicobacter pylori and improvement of gastritis. After four weeks of treatment, duodenal ulceration was healed in 16 (79%) of the patients; H. pylori was not detected by culture in 11 (50%) of the patients, and the associated gastritis improved in 12 (54%) patients. Four weeks after cessation of treatment the organism was cultured from antral biopsies of 18 (86%) of the patients and all of these had gastritis. Omeprazole treatment healed duodenal ulceration, improved gastritis temporarily, and suppressed but did not eradicate H. pylori.

Adult↗
PubMed1988

Value of surveillance cultures in the management of neutropenic patients.

To assess whether bacteriological surveillance cultures can be used to predict infection in neutropenic patients, cultures were performed during the period of neutropenia of nose, throat and urine specimens collected once weekly and faeces specimens collected twice weekly. Seventy-six consecutively observed patients undergoing chemotherapy for haematological or non-haematological diseases were investigated. Severe infection including septicaemia, lower respiratory tract infection, anorectal lesion and urinary tract infection occurred in 32 patients. Enterobacter cloacae, Escherichia coli and Pseudomonas aeruginosa were the organisms most commonly involved. In the majority of cases of septicaemia the organisms were isolated from the faeces, often in pure culture, prior to the onset of septicaemia. Most of the isolates of Enterobacter cloacae were resistant to the empiric antibiotic therapy used in the unit and were able to colonise multiple sites, presumably increasing the risk of subsequent infection. Faecal culture is the most useful approach in bacteriological surveillance in neutropenic patients.

Adolescent↗