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Biomedical subjects

J R Furr

Publications and source records attributed to J R Furr.

At least 37 records · Page 2Linked to original sources
PubMed1997

Aspects of the mechanisms of action of biguanides on trophozoites and cysts of Acanthamoeba castellanii.

A non-radioactive method was used to investigate the uptake by Acanthamoeba castellanii of chlorhexidine diacetate (CHA) and polyhexamethylene biguanide (PHMD). Based on the Giles et al. (1974) hypothesis, the uptake of CHA by trophozoites appeared to be of the L3 pattern whereas that of cysts was C2. Unlike CHA, trophozoites took up PHMB with an L2 pattern at low concentrations followed by a C-type pattern at higher concentrations, the uptake by cysts was found to be of the C2 pattern with a plateau effect at high concentrations. A diphasic leakage effect was found in trophozoites whereas a relatively low peak of maximal leakage occurred from cysts treated with high biocide concentrations. The amount of pentose release depended on the formulation ingredients. No correlation between pentose leakage and trophozoicidal or cysticidal activity was found.

Acanthamoeba↗
PubMed1996

The lethal effects of biguanides on cysts and trophozoites of Acanthamoeba castellanii.

The effects of a range of biocides on trophozoite and encysted forms of Acanthamoeba castellanii were investigated. Viable acanthamoebae were enumerated by a plaque assay technique. The cyst form of Acanthamoeba castellanii was more resistant to all biocides tested than the trophozoite form. Of the biocides tested, chlorhexidine diacetate (CHA) and polyhexamethylene biguanide (PHMB) were the most effective. Their lethal effects were time- and concentration-dependent. CHA was very effective when formulated in 0.1% EDTA combined with Tris buffer pH 7.8 whereas PHMB activity was reduced by 0.1% EDTA. Three per cent dimethylsulphoxide (DMSO) enhanced the activity of CHA but not of PHMB.

Acanthamoeba↗
PubMed1996

The possible role of yeast cell walls in modifying cellular response to chlorhexidine diacetate.

The relative porosity (RP) and thickness of cell walls of Saccharomyces cerevisiae depended upon the age of culture, the RP decreasing and the cell wall thickness increasing in older cultures. Chlorhexidine diacetate (CHA) produced cytological changes in S. cerevisiae cells, involving dense and granular cytoplasmic constituents, withdrawal of the interior from the cell wall and a general loss of the typical cellular organization. Cell wall mannan is unlikely to play a role in limiting the entry of CHA into yeast cells but changes in glucan composition, wall thickness and RP might be involved in determining the sensitivity of cells to the biguanide.

Anti-Infective Agents, Local↗
PubMed1995

Potentiation of the effects of chlorhexidine diacetate and cetylpyridinium chloride on mycobacteria by ethambutol.

Ethambutol enhanced the effects of chlorhexidine diacetate and cetylpyridinium chloride against Mycobacterium avium, M. bovis BCG, M. fortuitum and M. phlei. The findings show that it is possible to increase the susceptibility of mycobacteria to agents that normally exhibit poor activity against these organisms because of their reduced cellular penetration.

Anti-Infective Agents, Local↗
PubMed1995

Uptake of 14C-chlorhexidine gluconate by Saccharomyces cerevisiae, Candida albicans and Candida glabrata.

Uptake of radiolabelled chlorhexidine gluconate (14C-CHG) to Saccharomyces cerevisiae, Candida albicans and C. glabrata was very rapid and near maximal within 30 s. The organism, S. cerevisiae, most sensitive to the lethal action of chlorhexidine, took up significantly more biocide than the other organisms. Cells from cultures of different ages took up different amounts of 14C-CHG.

Anti-Infective Agents, Local↗
PubMed1995

X-ray microanalysis of chlorhexidine-treated cells of Saccharomyces cerevisiae.

The use of energy dispersive analysis of X-rays (EDAX) to identify and quantify the presence of chlorhexidine diacetate (CHA) within Saccharomyces cerevisiae cells was examined. Chlorine was used as the elemental marker tag. Saccharomyces cerevisiae cells exposed to 1000 micrograms ml-1 CHA took up increasing amounts of CHA over a time period of 30 s to 30 min. Electron probe micro-analysis was employed to examine the specific accumulation of CHA across the treated cells. These results showed that CHA was distributed evenly between the cell wall, cytoplasm and vacuoles of cells pre-treated with this concentration of CHA for 30 min. The EDAX system therefore provides a useful tool for examining the qualitative and quantitative effects of chlorhexidine on yeast cells, although quantitative data must be interpreted with caution.

Chlorhexidine↗
PubMed1994

Antibacterial activity of Actisorb Plus, Actisorb and silver nitrate.

Activated Charcoal Cloth with silver (Actisorb Plus) and solutions of silver nitrate, but not Actisorb (Activated Charcoal Cloth without silver), demonstrated antibacterial activity against Gram-negative and Gram-positive bacteria. This activity was unimpaired in the presence of plasma. Sodium thioglycollate was an effective neutralizer of Actisorb Plus and of silver nitrate, indicating that the release of silver from Actisorb Plus contributed to the antibacterial activity of the dressing.

Charcoal↗
PubMed1993

Antimycobacterial activity of 'Virkon'.

The peroxygen-based disinfectant, 'Virkon' (at concentrations of 2, 3 and 4%) was tested against Mycobacterium tuberculosis and M. avium-intracellulare over exposure times ranging between 30 and 120 min. Two test procedures were used: (a) a standard plate method, (b) a method incorporating the use of the 'Bactec' 460 radiometric system to chart bacterial growth following exposure to 'Virkon'. In our hands and under the conditions of the two test methods, 'Virkon' did not produce a satisfactory kill of the test strains over 60 or 120 min.

Disinfectants↗
PubMed1993

Effects of chlorhexidine diacetate and cetylpyridinium chloride on whole cells and protoplasts of Saccharomyces cerevisiae.

Chlorhexidine diacetate (CHA) and the quaternary ammonium compound, cetylpyridinium chloride (CPC), were fungicidal to Saccharomyces cerevisiae A364A and CHA to its mannoprotein mutant LB6-5D. Both CHA and CPC induced leakage of K+ and pentose material from both strains and both agents induced protoplast lysis as well as interacting with crude cell sap. Differences were observed between CHA and CPC in protoplast lysis and in cell sap interaction. Q25 values for A364A with CHA as test agent were 5.6 and 1.6 (fungicidal activity, depending on method of calculation), 1.46 (cell sap interaction) and 0.77 (leakage of pentoses). A sub-lytic concentration of CHA reduced considerably protoplast regeneration. Although the plasma membrane is an important target site for both agents, interaction with other cellular components also contributes to fungal death.

Cetylpyridinium↗
PubMed1992

Effects of chlorhexidine diacetate on Candida albicans, C. glabrata and Saccharomyces cerevisiae.

The effects of chlorhexidine diacetate (CHA) on Candida albicans, C. glabrata and wild-type and mannan, and permeability mutants of Saccharomyces cerevisiae have been studied. A CHA concentration of 10 micrograms/ml had little lethal activity against the Candida strains, but was more effective against S. cerevisiae. Concentrations of 100 and especially 1000 micrograms/ml brought about a much more rapid death of cells. 2-Mercaptoethanol enhanced the activity of CHA to some extent. Some of the mutant strains of S. cerevisiae were rather more sensitive than the wild-type strain. The age of cultures of C. albicans and C. glabrata influenced their response to CHA.

Candida↗
PubMed1988

Mechanism of resistance of Bacillus subtilis spores to chlorhexidine.

Chlorhexidine diacetate (CHA) was rather more sporicidal at 20 degrees C to urea-dithreitol-sodium lauryl sulphate (UDS)-treated spores of Bacillus subtilis NCTC 8236 than to urea-dithiothreitol (UDT)-treated or normal (untreated) spores. UDS spores adsorbed more CHA from solution than did the other two forms. No differences in hydrophobicity, as determined by hydrophobic interaction chromatography (HIC) or bacterial adherence to hydrocarbon (BATH), could be detected between the three spore types. Germinating spores took up much less CHA than did outgrowing spores. Germinating cells were considerably more hydrophobic, as measured by the BATH technique, than outgrowing cells or normal spores. Chlorhexidine diacetate increased the apparent hydrophobicity of the two latter forms, but this effect could be partially reversed by subsequent exposure to a non-ionic surfactant.

Bacillus subtilis↗
PubMed1987

Quenching of the antibacterial activity of chlorhexidine and benzalkonium by Letheen broth and Letheen agar in relation to wild-type and envelope mutant strains of gram-negative bacteria.

Letheen broth and Letheen agar have been investigated for their ability to act as neutralising and recovery media for wild-type and envelope mutants exposed to chlorhexidine diacetate and benzalkonium chloride. At high dilutions, untreated cells of the envelope mutant of Pseudomonas aeruginosa 799/61 were unable to produce colonies on Letheen agar. As a result of various procedures, it was concluded that dilution in Letheen broth and plating in Isosensitest agar was a suitable method for quenching cationic bactericides without harming the test strains, and that the increasing use of Gram-negative bacteria with outer membrane defects means that considerable care may be necessary in selecting media for evaluating bactericidal activity.

Benzalkonium Compounds↗
PubMed1986

Susceptibility of porin- and lipopolysaccharide-deficient strains of Escherichia coli to some antiseptics and disinfectants.

The sensitivities of some outer membrane protein (Omp) and/or lipopolysaccharide (LPS)-defective mutants of Escherichia coli to chlorhexidine and some quaternary ammonium compounds (QACs) were examined. Wild-type strains, with no defect in Omp or LPS were the most resistant to QACs, whereas LPS-deficient strains were the most sensitive. As expected, QAC resistance could not be related to the presence or absence of any specific porin(s). Chlorhexidine was highly active against all strains, inhibitory concentrations lying within the narrow range of 1 and 2 mg l-1.

Anti-Bacterial Agents↗
PubMed1986

Resistance of Providencia stuartii to chlorhexidine: a consideration of the role of the inner membrane.

Spheroplasts of three strains of Providencia stuartii (one sensitive, one moderately sensitive and one resistant to chlorhexidine) were induced by cefoxitin, glycine or a lysozyme-tris-EDTA combination, and their susceptibility to chlorhexidine-induced lysis investigated. Maximum lysis of spheroplasts occurred at a low (2.5-5 micrograms/ml) concentration of chlorhexidine and was greatest with the most sensitive strain, Pv2. The possible role of the inner membrane in chlorhexidine resistance is considered in the light of the findings obtained.

Bacteriolysis↗
PubMed1986

Reversal of the surface effects of chlorhexidine diacetate on cells of Providencia stuartii.

Chlorhexidine diacetate (CHA) increased the hydrophobicity of the cell surface of cells of three strains of Providencia stuartii. Removal of at least some of the CHA from the cells by washing them with an appropriate antidote partially reversed the hydrophobicity-increasing action of the biguanide. The effects of other treatments on cell surface hydrophobicity were examined with these strains and, for comparison, with two strains each of Escherichia coli and Pseudomonas aeruginosa: ethylenediamine tetraacetic acid affected all strains, although not to the same extent, whereas thermal injury (55 degrees C) produced marked changes only with the two E. coli strains.

Cell Membrane↗