In-situ inhibicija Staphylococcus aureus bakterijama mliječne kiseline iz dva tradicionalna slovenska sira proizvedena od sirovog mlijeka

Bacteriocin(s) producing lactic acid bacteria naturally present in traditional cheeses represent an inexhaustive pool of microbes with safeguarding potential. Some bacteriocins produced by cheese lactic acid bacteria were already described as successful anti-staphylococcal agents. The presence of genes for bacteriocins with potential anti-staphylococcal activity was also demonstrated in two Slovenian traditional raw milk cheeses, “Tolminc” and “Kraški ovčji sir”. Same bacteriocin genes were also detected in viable lactic acid bacteria consortia’s isolated from “bacteriocin positive cheeses” on Rogosa, M17 and CATC agar media. The aim of the research was to elucidate whether or not this particular cheese consortia, in which bacteriocin genes were detected, actually exhibit anti-staphylococcal activity in milk and/or cheese. For this purpose different cheese consortia were selected in relation to versatility of detected bacteriocin genes and used to perform challenge tests against Staphylococcus aureus in milk and cheese. In milk following the time/temperature regime of traditional cheese production all cheese consortia effectively inhibited growth of Staphylococcus aureus in the range of app. 2 to 3 log. In cheese the inhibition of staphylococci was less pronounced but still evident since inhibition of app. 1.5 log was detected. Sole inhibition by lactic acid production was ruled out while linking inhibition directly to bacteriocin production would take some additional work.Bakterije mliječne kiseline (BMK), prirodno prisutne u tradicionalnim sirevima, predstavljaju neograničen izvor mikroba sa zaštitnim svojstvima. Za neke bakteriocine, koje proizvode BMK iz sira, antistafilokokna svojstva već su poznata. Prisutnost gena za bakteriocine s antistafilokoknim svojstvima potvrđena je u dva tradicionalna slovenska sira iz sirovog mlijeka; to su sir “Tolminc” i “Kraški ovčji sir”. Prisutnost istih bakteriocina potvrđena je i kod bakterija mliječne kiseline, koji su izolirali iz tih sireva na agar podlogama Rogosa, M17 i CATC. Cilj je bio provjeriti da li izolirani sojevi bakterija mliječne kiseline, koji nose gene za bakteriocine, zaista pokazuju antistafilokokna svojstva u mlijeku i/ili siru. Na temelju prisutnih gena za bakteriocine ispitana je antimikrobna aktivnost združene kulture bakterija mliječne kiseline prema bakteriji Staphylococcus aureus u mlijeku i siru. U mlijeku kojeg smo podvrgnuli vremensko-temperaturnom režimu proizvodnje tradicionalnih sireva, združena kultura bakterija mliječne kiseline inhibirala je rast bakterije Staphylococcus aureus u rasponu od 2 do 3 logaritamske jedinice. U siru je inhibicija stafilokoka bila nešto manje izražena, ali još uvijek očita sa 1,5 logaritamskih jedinica slabijim rastom S. aureus nego u kontrolnom siru. Učinak inhibicije izazvane mliječnom kiselinom bio je isključen, ali bi bilo potrebno izvesti još dodatna ispitivanja, da se utvrdi izravno inhibicijsko djelovanje bakteriocina na stafilokoke