The effect of low-intensity laser radiation on the sensitivity of Staphylococcus aureus to some halogen-containing azaheterocycles

The rapid rate of acquisition and spread of resistance to antibiotics by microorganisms leads to the search and investigation of new ways of combating infectious agents. Being a modern, minimally invasive method with an almost complete absence of side effects, the use of low-intensity laser radiation can be considered as one of the alternatives to traditional antibiotic therapy. At the same time, the search for new chemical compounds with pronounced antimicrobial activity is also promising. The impact of low-intensity laser of the red spectrum (lambda = 660 nm) on the sensitivity of a clinical isolate of Staphylococcus aureus to newly synthesized halogen- and chalcogen-halogencontaining derivatives of the quinazoline and benzothiazole series was studied using the serial microdilutions method with the determination of minimal inhibitory and minimal bactericidal concentrations. To evaluate the antimicrobial properties of the investigated substances in dynamic, we investigated their activity two months after the synthesis with subsequent comparison to freshly synthesized compounds. The research results indicate that the most pronounced antimicrobial effect was shown by trichlorotelluromethylthiazoloquinazolinium chloride and propargylthiobenzothiazolium hexachlorotellurate. Evaluating the dynamics of the activity of the studied compounds, it was noted that the absolute majority of substances retained their properties, which indicates their stability. When evaluating the effect of irradiation of microbial inoculum with low-intensity laser radiation on the susceptibility to chemical compounds, an increase in the sensitivity of irradiated microorganisms to some investigated chemicals was noted compared to similar non-irradiated microbial suspensions. In the case of 2 out of 9 studied chemical compounds we noted a 2- to 4-fold decrease in the minimal inhibitory concentration for irradiated microbial suspensions. A decrease in the minimal bactericidal concentration after irradiation was noted for one of the substances. In the cases of butynylthiobenzothiazolium hexabromotellurate, and tribromotelluromethylthiazoloquinazolinium bromide, decrease of both minimal inhibitory and minimal bactericidal concentrations in the irradiated inoculum was observed. The above shows that low-intensity laser radiation under certain parameters increases the susceptibility of microorganisms to antimicrobial agents.