Introduction: Listeria monocytogenes strains are widespread in the natural environment and are the etiological factor of listeriosis. Food is the main source of L. monocytogenes. Secondary contamination of food products which results from the formation of biofilm by L. monocytogenes on the surfaces of the processing devices makes an essential problem.

Material and methods: We evaluated the ability of biofilm formation in media supplemented with sheep blood (in a volume of 5.0, 10.0, 20.0 and 50.0%) for the reference strain L. monocytogenes ATCC 7644 and strains isolated from the human blood and carrots on the polypropylene surface.

Results: The strain isolated from blood most efficiently formed a biofilm with increasing blood sheep’s addition (nutrient broth — 4.87 × 105 CFU × cm-2, blood supplement 50.0% (v/v) — 3.4 × 107 CFU × cm-2).The number of L. monocytogenes recovered from the biofilm for the reference strain and the strain from carrot increased to 20.0% by volume of the blood addition (3.07 × 105 CFU × cm-2 and 4.03 × 105 CFU × cm-2 respectively — nutrient broth; 1.1 × 107 CFU × cm-2 and 9.23 × 106 CFU × cm-2 — blood supplement 20.0% (v/v)). Decrease in the number of cells recovered from the biofilm for the reference strain and the one isolated from carrot has been demonstrated at 50.0% addition of blood into nutrient medium (8.8 × 106 CFU × cm-2 and 7.87 × 106 CFU × cm-2 respectively).

Conclusion: The addition of sheep blood to the medium at concentrations up to 20.0% increases the number of cells recovered from the biofilm for all studied L. monocytogenes strains whereas medium with 50.0% blood stimulates the biofilm formation only by the strain isolated from blood.