Snail mucus is suggested to have the ability to act as an antimicrobial and anti-inflammatory agent as well as to stimulate cell regeneration. The purpose of this master thesis was to investigate the effect of snail mucus collected from garden snails (Helix aspersa Müller) on cell growth and biofilm formation of bacteria Staphylococcus aureus and Pseudomonas aeruginosa in an optimized testing system. S. aureus and P. aeruginosa are opportunistic pathogens often isolated from chronic wounds. They can cause a wide range of local and systematic infections in humans. Their treatment is becoming increasingly challenging due to the emergence of drug resistance. Therefore, many studies are focused on finding new approaches of infection control. In our thesis, we first optimized a system for testing the effect of snail mucus on cell growth and biofilm formation. As part of the optimization, we tested two types of polystyrene 96-well plates (flat and curved bottom), three different media (LB, BHI, TSB) without added glucose and with two different glucose concentrations (0.2 and 2 %) and optimized preparation of testing culture (with/without shaking during growth and time of culture growth prior testing). We tested the effects of snail mucus on two out of seven S. aureus strains and two out of six P. aeruginosa strains isolated from chronic wounds, which produced the highest amounts of biofilm. The testing was conducted on non-shaked 10-hour bacterial cultures in the exponential growth phase using following system parameters: curved bottom 96-well plate, BHI medium for P. aeruginosa and BHI with 2 % glucose for S. aureus. We found that natural snail mucus filtrate does not inhibit any cell growth nor any biofilm formation. On contrary, it can stimulate growth and biofilm formation in some cases, especially in P. aeruginosa.