Influence of antibiotics on biofilm formation by Streptococcus pyogenes in vitro

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.