The search for novel modifications of culture media aimed at culture prolongation is a prerequisite for microbiological diagnostic progress.The aim of the studywas to assess the possibilities of applying dimethicone (polymethylsiloxane) as a barrier between the agar surface and atmosphere to prevent drying of solid and semisolid culture medium providing the retention of its useful properties.Materials and MethodsWe studied the dynamics of water (volume) loss of culture media used in microbiology, and the effect of dimethicone on the process. Dimethicone was arranged in layers on culture medium surface. The effect of dimethicone on growth and generation of fast-growing (Staphylococcus aureus,Escherichia coli,Salmonella entericaSerovar Typhimurium,Burkholderia cenocepacia) and slow-growing (Mycobacterium avium) bacteria was studied, as well as on bacterial mobility (Pseudomonas aeruginosaandEscherichia coli) in semisolid agars.ResultsThe dynamics of water loss in culture media showed the weight loss in all media without dimethicone (control) in 24 h to be statistically significant (p<0.05); 7–8 days later, they lost 50% of weight, and 14 days later they lost approximately 70%. The weight of media under dimethicone underwent no significant changes during the observation period. Growth index of fast-growing bacteria (S. aureus,E. coli,S.Typhimurium,B. cenocepacia) on control culture media without applying any substance, and on culture media under dimethicone had no significant differences. VisibleM. aviumgrowth on chocolate agar in controls was recorded on day 19, under dimethicone — on days 18–19. The number of colonies on culture day 19 under dimethicone tenfold exceeded the control values. The mobility indices ofP. aeruginosaandE. colion semisolid agar under dimethicone 24 h later were significantly higher than under control conditions (p<0.05 in both cases).ConclusionThe study confirmed marked deterioration of culture media properties under prolonged cultivation. The suggested protection technology of culture media growth properties using dimethicone showed beneficial effects.