Background. In terms of serological properties and immunization, the wild type of HBsAg HBV and its G145R mutant behave as different antigens. This testifies to serious structural changes, which presumably could have a significant impact on the morphogenesis of virions and subviral particles. Nevertheless, morphological and ultrastructural investigations of HBV with G145R mutation have not been carried yet. Objectives. Research of structural and morphological organization of HBV in the presence of the G145R escape mutation. Methods. Studies of sera, purified viruses and recombinant HBsAg were carried out by transmission electron microscopy by the method of negative staining and indirect reaction of immunelabeling using monoclonal antibodies of different specificity. Specimens of wild type HBV and HBV with S143L mutation obtained in an identical manner were used as the control. Results. The presence of typical virus particles of HBV was shown in the specimens of wild strain and HBV with S143L mutation. Specimens of HBV with G145R mutation were characterized by expressed morphological heterogeneity. In the initial serum and in the specimen of purified virus containing G145R mutant, large oval particles 60-70 nm and up to 200 nm in size, respectively, were found. The presence of antigen structures of HBV in all heterogeneous forms was confirmed. It was shown that forming of subviral particles in the process of expression of the recombinant HBsAg with G145R mutation depends on conditions of expression and purification of the protein. They can vary from well-formed circular and oval particles to practically unstructured fine-grained masses. Conclusion. Direct data on the impact of G145R escape-mutation in S-gene, in contrast to S143L mutation, on the morphogenesis of virions and subviral particles of HBV were obtained.

Aim. To study the effect of the antibiotics oxacillin and cefazolin on culture growth and biofilm formation of Streptococcus pyogenes type 30M in vitro.Materials and methods. The formation of biofilms was studied in light and scanning electron microscope, on sterile cover glasses using special nutrient medium. To identify the biofilm, experimental samples were stained with alcohol-water solution of alcian blue.Results. Small quantitative doses (0.01–0.1 mg) of oxacillin and cefazoline, regardless of the duration of the exposure, did not have a negative effect both on the biofilm formation process and the formed streptococcal biofilm. An increase in quantitative doses of antibiotics to 0.5–1.0 mg at the stage of formation of Streptococcus biofilm had an inhibitory effect on the growth of microbial cells and the formation of biofilm. The integrity of streptococcal chains and biofilm was preserved when oxacillin and cefazoline were applied at a quantity of 0.5–1.0 mg to the formed biofilm. However, in some cases, the twisting of the chains in spherical shape with visible colored biofilm inside was observed. In addition, there was a stimulating effect of cefazoline on the formed Streptococcal biofilm. When the formed biofilm was exposed to high doses of antibiotics (2 mg or higher), a break of streptococcal chains was observed, while oxacillin had a destructive effect on the microbial biofilm. In similar experiments with cefazolin, the biofilm was preserved, despite the fact that the destruction of microbial chains was also observed.Conclusion. Significant differences were found in the effect of tested antibiotics on both the mature S. pyogenes type 30M biofilm and the biofilm formation process.

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