Susceptibility of Pseudomonas aeruginosa to a photodynamic effect of the arginine hematoporphyrin derivative.

The photodynamic effect of the arginine hematoporphyrin derivative (HpD-Arg(2)) on the growth of selected Pseudomonas aeruginosa clinical isolates is described as compared to the effect of hematoporphyrin derivative (HpD). Growth inhibition of HpD-Arg(2) of three Gram-positive strains (Staphylococcus aureus, Bacillus subtilis and Micrococcus luteus) and five laboratory strains of Gram-negative bacteria (Escherichia coli, Proteus vulgaris, P. aeruginosa, Klebsiella pneumoniae and Enterobacter cloacae) was observed as well. Serratia marcescens strain was resistant to light-activated HpD-Arg(2) or HpD. The antimicrobial activity of light-activated HpD-Arg(2) against P. aeruginosa may offer an additional option in the anti-pseudomonal therapy of wounds.

Contribution to the mechanism of liquid membrane oscillators involving cationic surfactant.

It is shown that liquid membrane oscillators with cationic surfactants have more complex oscillation patterns than observed previously. The actual details of the oscillations depend strongly on the nature of the membrane material, disclosing even the presence of parallel molecular events. It appears that sampling topology also has a great influence on the observed oscillatory behavior. Variation of oscillation patterns with diffusion path length in the membrane demonstrated the decisive role played by the actual timing of molecular events. The new evidences produced complete usefully the actual views concerning the mechanism of oscillations.

Molecular mechanism and chemical kinetic description of nitrobenzene liquid membrane oscillator containing benzyldimethyltetradecylammonium chloride surfactant.

Nonlinear oscillations of electric potential differences caused by mass transfer of benzyldimethyltetradecylammonium chloride through a nitrobenzene liquid membrane containing picric acid are investigated. The physical chemistry of this liquid membrane oscillator is described in detail, and limitations of applicability of some physicochemical laws are pointed out. It is shown that the oscillations are of chemical origin. The role of the accompanying hydrodynamic effects is critically examined. In order to understand the oscillation mechanism at the molecular level, a new mechanistic scheme based on ion pairs mass transfer is proposed. Oscillations appear at the membrane-aqueous acceptor phase interface, and they are caused by the autocatalytic adsorption of surfactant molecules to this interface. Inclusion of cross-catalytic molecular events shows interesting coupling between diffusion fluxes and the two oscillating subsystems present. It is demonstrated that the proposed mechanistic scheme is quite general and versatile. Time evolution of the oscillator is described by using the laws of deterministic chemical kinetics. The results obtained by numerical integration of the corresponding system of first-order autonomous differential equations are in fairly good agreement with experimental time series. It is postulated accordingly that the nonlinear oscillations observed for liquid membrane systems are originating from molecular events and are further amplified by hydrodynamic effects.

A novel multiplex PCR assay for the detection of Salmonella enterica serovar Enteritidis in human faeces.

AIMS: To develop a multiplex PCR assay for the detection of Salmonella enterica serovar Enteritidis in human faeces. METHODS AND RESULTS: A total of 54 Salmonella strains representing 19 serovars and non-Salmonella strains representing 11 different genera were used. Five primer pairs were employed in the assay. Three of them targeted to the genes hilA, spvA and invA that encode virulence-associated factors. A fourth primer pair amplified a fragment of a unique sequence within S. enterica serovar Enteritidis genomes. An internal amplification control (a fragment of a conservative sequence within the 16S rRNA genes) was targeted by a fifth primer pair. The assay produced two or three amplicons from the invA, hilA and 16S rRNA genes for 19 Salmonella serovars. All Salmonella and non-Salmonella strains yielded a band of an internal amplification control. For S. enterica serovar Typhimurium, four products (the fourth from the spvA gene), and for S. enterica serovar Enteritidis five amplicons (the fifth from the sdf gene) were observed. S. enterica serovar Enteritidis was cultured from three of 71 rectal swabs from diarrhoeal patients. Five specific amplicons were generated with the multiplex PCR assay only from culture-positive faecal samples. CONCLUSION: The multiplex PCR assay specifically detects S. enterica serovar Enteritidis. SIGNIFICANCE AND IMPACT OF THE STUDY: This is a novel multiplex PCR assay, which contains an internal amplification control and enables concurrent survey for Salmonella virulence genes.

Examination of antibacterial activity of the photoactivated arginine haematoporphyrin derivative.

The antibacterial photodynamic effect of arginine haematoporphyrin derivative (HpD-Arg2) was investigated using two methods. The effect proved to be highly antibacterial when it was employed against P. aeruginosa and S. aureus cells floating in the nutrient broth. The reduction of approximately four logarithms of CFU ml-1 after light exposition, as compared to a dark control, was observed. In the second step of the study the photodynamic effect was employed against the same strains of bacteria after their colonization on isolated mouse muscles. In this case the antibacterial effect was observed as well. However, the reduction of CFU ml-1 achieved was much lower and reached one logarithm only. The optimal concentration of photoactivated HpD-Arg2 for S. aureus and P. aeruginosa was 25 microg ml-1 and 800 microg ml-1 for the floating bacteria, and 200 microg ml-1 and 1000 microg ml-1 for sessile bacteria, respectively. We have concluded from our study that the antibacterial effect investigated may offer, in the future, an alternative method for treatment of the tissues superficially infected with pathogens resistant to antibiotics. However, further studies in this field are necessary.

Photodynamic activity of the haematoporphyrin derivative with rutin and arginine substituents (HpD-Rut(2)-Arg(2)) against Staphylococcus aureus and Pseudomonas aeruginosa.

The impact of the new photosensitizer HpD-Rut(2)-Arg(2)on the growth of methicillin-resistant Staphylococcus aureus(MRSA), methicillin-susceptible Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa clinical strains isolated from infected burn wounds was examined. The susceptibility of the isolates to the photodynamic action of the sensitizer was evaluated by the determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using the newly developed microdilution method. The results were compared with the previously investigated HpD-Arg(2). All clinical isolates examined proved to be susceptible to the photodynamic action of HpD-Rut(2)-Arg(2). The MIC of this newly synthetized photosensitizer ranged from 0.8 to 12.5 microg ml(-1) for MRSA, from 0.4 to 6.2 microg ml(-1) for MSSA and from 6.2 to 50 microg ml(-1) for P. aeruginosa. While MBC ranged from 1.6 to 12.5 microg ml(-1) for MRSA, 0.4 to 6.2 microg ml(-1) for MSSA and 6.2 to 100 microg ml(-1) for P. aeruginosa. This photosensitizer is more effective in its bactericidal photodynamic action than previously tested HpD-Arg(2).