Assessment of the Effect of Relativistic Electron Streaming on Biological Properties of Pseudomonas Aeruginosa Strains

Pseudomonas aeruginosa belong to a group of non-fermenting gram-negative bacteria (NFGNBs) with ubiquitous distribution, hardy and resistant to disinfectant solutions. The clonal link between clinical and isolated from hospital environment P. aeruginosa strains, which are believed to be the main source of infection in the hospital, has been confirmed. An alternative to commonly used technologies of decontamination and sterilization of various objects is now the method of decontamination using an electron beam. The treatment of materials contaminated with microorganisms by a stream of relativistic electrons has a number of advantages over traditional technologies, namely instantaneous action, lack of consumables, safety, low power consumption, universality, lack of thermal effect, etc. The purpose of the study was to determine the effect of the relativistic electron streaming on biological (growth, culture, biochemical, persistent) properties of P. aeruginosa strains in model objects. Material and methods. Reference strains of P. aeruginosa ATCC 27853 and 5 circulating strains isolated from the internal environment of a surgical hospital were used as test strains. Physical part of work (irradiation of objects by relativistic electrons streaming) was carried out at the National Research Centre “Kharkiv Physical-Technical Institute” of the National Academy of Sciences of Ukraine. We used a linear resonance pulsed electron accelerator with a beam-measuring system, on a wavelength running at 2850 MHz, assembled according to the traditional scheme. The irradiation of model objects by streaming the relativistic electrons was carried out at a distance of up to 30 cm from the accelerator outlet. Results and discussion. We determined the modes of the electronic accelerator, providing bacteriostatic and bactericidal effect on Pseudomonas aeruginosa test strains in model samples. As a result a practically linear dose-reduction dependence of viable bacteria was established. Bacteriostatic aftereffect of the electron beam was observed at energy loads from 0.8 to 3.8 kGy. Bactericidal effect was observed after irradiation of test strains by doses starting from 4.0 kGy. Irradiation of model samples with sublethal doses of relativistic electrons was shown to result in the appearance of phenotypic modifications in 10.0-20.0%, characterized by disappearance or reduction in the activity of certain enzymes typical for test strains of P.aeruginosa. 25.0% of the 32 biochemical features under investigation were found to have no fermentation of L-rhamnose, N-acetylglucosamine and acetate. The indicated changes did not depend on the dose of irradiation of the strains by an electron beam. Conclusions. All the detected phenotypic changes disappeared through 1-3 passages of cultures; that is, they were non-hereditary. Indices of adhesive activity of strains after irradiation did not have statistically significant changes. We also noted the inhibition of the biofilm-forming ability of the test strains of Pseudomonas aeruginosa by 1.7-6.6 fold.