Characterization of autochthonous Enterococcus species isolated from traditionally produced cheeses

U ovom radu provedena je izolacija autohtonih bakterija mliječne kiseline (BMK) iz tradicionalno proizvedenih sireva s ciljem odabira predstavnika Enterococcus vrsta kao potencijalnih probiotičkih starter kultura. Pomoću klasičnih mikrobioloških metoda odabrani autohtoni izolati su okarakterizirani kao gram-pozitivni, katalaza-negativni, nesporogeni, kuglasti, koji uspješno spuštaju pH vrijednost hranjive podloge, te sintetiziraju visoke koncentracije mliječne kiseline. Provedena je genotipska identifikacija sekvencioniranjem 16S rRNA gena prema kojoj je među odabranim autohtonim BMK bilo prisutno 7 različitih bakterijskih sojeva iz roda Enterococcus. Autohtoni sojevi BMK BGRE 2-24, BGRE 2-43 i BGBU 1-42 najbolje preživljavaju simulirane uvjete gastrointestinalnog trakta. Ispitivanjem osjetljivosti Enterococcus vrsta na 12 različitih antibiotika, utvrđeno je da Enterococcus faecalis / durans / faecium BGBU 1-41 nije osjetljiv na neomicin i streptomicin, kao i sojevi Enterococcus faecalis BGRE 2-24 i Enterococcus faecium/ durans BGRE 2-57, dok Enterococcus faecium / durans BGBU 1-42 i Enterococcus hirae / faecium BGRE 2-43 nisu osjetljivi na streptomicin, ali jesu na neomicin koji također pripada skupini aminoglikozidnih antibiotika.In this paper isolation of the autochthonous isolates of lactic acid bacteria (LAB) from traditionally produced cheeses was performed aimed to select representatives of Enterococcus species with a potential as probiotic starter cultures. Selected autochthonous isolates were characterized as gram-positive, catalase-negative sphere-shaped bacteria by conventional microbiological methods, which were successfull in lowering pH value of the medium and synthesized high concentrations of lactic acid. Identification performed by 16S rRNA gene sequencing revealed that between selected autochthonous LAB 7 different strains were identified as representatives of Enterococcus. Autochthonous LAB BGRE 2-24, BGRE 2-43 and BGBU 1-42 showed high survival rates in simulated gastrointestinal tract conditions. Investigation of the susceptibility to different antibiotics revealed that Enterococcus faecalis / durans / faecium BGBU 1-41, Enterococcus faecalis BGRE 2-24 and Enterococcus faecium / durans BGRE 2-57 were not sensitive to neomycin and streptomycin while strain Enterococcus faecium / durans BGBU 1-42 and Enterococcus hirae / faecium BGRE 2-43 were resistant to neomycin but not to streptomycin which are all aminoglycoside antibiotics