Biomedical subjects

I S Al-Adham

Publications and source records attributed to I S Al-Adham.

4 recordsLinked to original sources

PubMed2000

Microemulsions are membrane-active, antimicrobial, self-preserving systems.

Microemulsions are physically stable oil/water systems that have potential use as delivery systems for many pharmaceuticals which are normally of limited use due to their hydrophobicity, toxicity or inability to access the site of action. It has been suggested that microemulsions are self-preserving antimicrobials in their own right, although there is little evidence to support this. In this experiment, microemulsions of various compositions were formulated and tested for their stability and antimicrobial action. The physical stability of the different microemulsions was assessed by centrifugation at 4000g and by storage in a water bath at 37 degrees C for one month, during which no phase separation was observed. The antimicrobial activity of the microemulsions was tested using the compendial method, observation of the kinetics of killing, and transmission electron microscopy (TEM) of microemulsion-exposed cultures of Pseudomonas aeruginosa PA01. These latter experiments on Ps. aeruginosa indicated distinct signs of membrane disruption. The results indicated that the microemulsions are self-preserved, and that their killing of microbial cultures is very rapid and may be the result of membrane activity.

Anti-Bacterial Agents↗

PubMed2000

Outer membrane protein shifts in biocide-resistant Pseudomonas aeruginosa PAO1.

Benzisothiazolone (BIT), N-methylisothiazolone (MIT) and 5-chloro-N-methylisothiazolone (CMIT) are highly effective biocidal agents and are used as preservatives in a variety of cosmetic preparations. The isothiazolones have proven efficacy against many fungal and bacterial species including Pseudomonas aeruginosa. However, some species are beginning to exhibit resistance towards this group of compounds after extended exposure. This experiment induced resistance in cultures of Ps. aeruginosa exposed to incrementally increasing sub-minimum inhibitory concentrations (MICs) of the isothiazolones in their pure chemical forms. The induced resistance was observed as a gradual increase in MIC with each new passage. The MICs for all three test isothiazolones and a thiol-interactive control compound (thiomersal) increased by approximately twofold during the course of the experiment. The onset of resistance was also observed by reference to the altered presence of an outer membrane protein, designated the T-OMP, in SDS-PAGE preparations. T-OMP was observed to disappear from the biocide-exposed preparations and reappear when the resistance-induced cultures were passaged in the absence of biocide. This reappearance of T-OMP was not accompanied by a complete reversal of induced resistance, but by a small decrease in MIC. The induction of resistance towards one biocide resulted in the development of cross-resistance towards other members of the group and the control, thiomersal. It has been suggested that the disappearance of T-OMP from these preparations is associated with the onset of resistance to the isothiazolones in their Kathon form (CMIT and MIT).

Bacterial Outer Membrane Proteins↗

PubMed1998

Pyrithione biocide interactions with bacterial phospholipid head groups.

Sodium pyrithione and zinc pyrithione (NaPT and ZnPT, respectively) are antimicrobial agents widely used in both the cosmetics and fuel industries. They are also utilized in the mining industry because of their metal chelating properties. They have been shown to depolarize membrane electropotential in fungi and are also known to inhibit fungal and bacterial substrate transport processes. Recent work has shown that both pyrithiones cause the leakage of intracellular material (potassium ions and O.D.260 nm absorbing material) from exposed bacterial cells. The work here reports studies on the interactions between the pyrithiones and the bacterial phospholipid head group structures, at both a practical and a theoretical level, utilizing tube dilution neutralizer studies, scanning spectrophotometry and molecular modelling. The tube dilution neutralizer studies exhibited a decrease in minimum inhibitory concentration (MIC) for both pyrithiones in the presence of extracellular phosphatidyl-ethanolamine and EDTA. Scanning spectrophotometry exhibited the chelation of the central zinc atom from the ZnPT chelate by the addition of EDTA. Molecular modelling studies exhibited the chelation of the phosphatidyl-ethanolamine head group by ZnPT. Zinc pyrithione also exhibited an interaction with the ammonium tail of the head group structures. Sodium pyrithione exhibited electrostatic interactions with the phospholipid head groups in the molecular modelling studies.

Antifungal Agents↗

PubMed1998

Pyrithione biocides as inhibitors of bacterial ATP synthesis.

Sodium pyrithione and zinc pyrithione (NaPT and ZnPT, respectively) are widely used as cosmetic preservatives and general antimicrobial agents. They have been shown to be active against fungal cell walls, associated membranes and bacterial transport processes. Investigations were undertaken into the effect of these antimicrobial agents on substrate catabolism and intracellular ATP levels using an oxygen electrode and luciferin-laciferase technology, respectively. Results indicate that, while both compounds are poor inhibitors of substrate catabolism, sub-inhibitory concentrations of biocide greatly reduces intracellular ATP levels in both Escherichia coli NCIMB 10000 and Pseudomonas aeruginosa NCIMB 10548. This is thought to be due to the action of NaPT and ZnPT on the Gram-negative bacterial membrane.

Adenosine Triphosphate↗