Osim primjene u industrijskim fermentacijama, bakterije mliječne kiseline (BMK) čine važan dio mikrobne populacije prirodnih ekosustava poput urogenitalnog i gastrointestinalnog trakta ljudi i životinja. U ovakvom mikrookolišu značajno je ihhibicijsko djelovanje BMK prema nepoželjnim mikroorganizmima. Pojedini predstavnici BMK upravo su definirani i kao probiotici koji doprinose poboljšanju ljudskog i životinjskog zdravlja na prirodan način, a upravo antagonističko djelovanje prema nepoželjnim i patogenim mikroorganizmima je jedno od najvažnijih funkcionalnih svojstava. U ovom radu istraženo je antimikrobno djelovanje probiotičih sojeva Lactobacillus helveticus M92, Lactobacillus plantarum L4 i Enterococcus faecium L3, prema šest različitih test mikroorganizmima: Staphylococcus aureus 3048, Staphylococcus aureus K-144, Escherichia coli 3014, Salmonella enterica serovar Typhimurium FP1, Bacillus subtilis ATCC 6633 i Bacillus cereus TM2. Svi probiotički sojevi iskazuju snažno antimikrobno djelovanje prema testiranim mikroorganizmima, što je važno funkcionalno svojstvo probiotičkih sojeva i jedan od bitnih mehanizama kompetitivne ekskluzije koja im daje selektivnu prednost pred patogenima u specifičnom mikrokolišu poput gastrointestinalnog trakta domaćina.

Beyond their involvement in industrial fermentations, LAB make part of natural ecosystems such as the urogenital or the gastro-intestinal tract of humans and other animals. In these microenvironments, LAB also play a role in the inhibition of pathogenic microorganisms. Some species of LAB reportedly have a beneficial role on health and wellbeing of the host. Some members of those bacteria are also defined as probiotics which increase human and animal health on natural way. Desirable property of lactic acid bacteria starter cultures and probiotic strains is their antagonistic effect on undesirable and pathogen microorganisms. In this work, antibacterial activity of three probiotic strains Lactobacillus helveticus M92, Lactobacillus plantarum L4 and Enterococcus faecium L3 has been examined, using the turbidimetric method towards six different test-microorganisms: Staphylococcus aureus 3048, Staphylococcus aureus K-144, Escherichia coli 3014, Salmonella enterica serovar Typhimurium FP1, Bacillus subtilis ATCC 6633 i Bacillus cereus TM2. All probiotic strains exhibit strong antimicrobial activity against test microorganisms, what is an important functional propertie and one of the major mechanisms of competitive exclusion. Final results indicate bacteriocin activity of examined probiotic strains.