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Namen magistrske naloge je bil raziskati odpornost proti antibiotikom eritromicinu, tetraciklinu in kanamicinu med laktobacili, izoliranimi iz sirov. V raziskavi smo uporabili 34 vzorcev sirov, dostopnih na slovenskem tržišču, iz katerih smo osamili 176 izolatov. Z analizo RAPD-PCR smo izolate pregledali in med izolati z istim vzorcem pomnožkov izbrali po enega za nadaljnjo analizo. 106 izolatov z različnimi vzorci pomnožkov smo najprej identificirali na nivoju vrste in ugotovili, da je največ sevov pripadalo vrstama Lactobacillus (L.) plantarum (26) in L. paracasei (22), 18 sevov vrsti Pediococcus pentosaceus in 1 sev vrsti Bifidobacterium animalis subsp. lactis. Fenotipsko odpornost smo ugotavljali z metodo razredčevanja v mikrotitrski ploščici. Ker so pri 70 sevih dobljene vrednosti minimalne inhibitorne koncentracije presegle vrednosti, predpisane s strani EFSA, smo z metodo PCR pri njih preverili še morebitno prisotnost genov z zapisi za odpornost proti antibiotikom: tet(A), tet(B), tet(C), tet(M), tet(O), tet(W), ermA, ermB, ermC, ermT, aph(3')-llla, aac(6')-aph(2'') in ant(6)-la. Vseh 70 odpornih sevov je izkazalo fenotipsko odpornost proti kanamicinu, proti eritromicinu pa je bilo odpornih 5 sevov iz vrst L. parabuchneri, L. capillatus, L. plantarum, P. pentosaceus in L. paracasei, vendar pri nobenem sevu nismo potrdili prisotnosti preiskovanih genov. Odpornost proti tetraciklinu je izkazalo 9 sevov, prisotnost genov tet(A) in tet(M) smo potrdili le pri sevu vrste L. capillatus. Ugotovili smo, da laktobacili iz sirov ne predstavljajo resnejšega tveganja za horizontalen prenos genov, vendar je vseeno potrebno preverjanje odpornosti proti antibiotikom pri mlečnokislinskih bakterijah. The aim of the study was to investigate antibiotic resistance of erythromycin, tetracycline and kanamycin among lactobacilli isolated from cheese. We used 34 samples of cheese available on the Slovenian market, from which we isolated 176 isolates. Isolates were analysed by using RAPD-PCR and among isolates with the same RAPD-PCR band pattern, one was selected for further analysis. 106 isolates with different band pattern were first identified at species level and it was revealed that most strains belonged to the species of Lactobacilus plantarum (26) and L. paracasei (22), 18 strains belonged to Pediococcus pentosaceus species and 1 strain to Bifidobacterium animalis subsp. lactis species. Phenotypic resistance was determined by the microdilution method. 70 strains exerted MIC values above the cut-off values proposed by EFSA. Therefore, PCR was carried out to search for antibiotic resistance genes as follows: tet(A), tet(B), tet(C), tet(M), tet(O) , tet(W), ermA, ermB, ermC, ermT, aph(3')-llla, aac(6')-aph(2'') in ant(6)-la. Among resistant strains, all 70 strains revealed phenotypic resistance to kanamycin, while 5 strains, belonging to L. parabuchneri, L. capillatus, L. plantarum, P. pentosaceus and L. paracasei were resistant to erythromycin, but none of the strains carried the investigated antibiotic resistance genes. Resistance to tetracycline showed 9 strains but the presence of genes tet(A) and tet(M) was found only in the strain of L. capillatus. We can conclude that there is no serious risk of horizontal gene transfer between investigated lactobacilli, but there is still necessity to test LAB for antibiotic resistance.