The invention relates to an antibiotic substance of microbial origin, arbitrarily denominated antibiotic 107891 which is produced by fermentation of Microbispora sp. ATCC PTA-5024, the pharmaceutically acceptable salts and compositions thereof, and their use as an antibacterial agent having inhibitory activity versus susceptible microbes. Antibiotic 107891, which is a complex comprising two Factors, denominated Factors Al and A2, has a peptide structure containing lanthionine and methyllanthionine as constituents which are typical characteristics of the antibiotics of the lantibiotics group. Antibiotic 107891 and its Factors Al and A2 show a good antibacterial activity against Gram-positive bacteria including methicillin resistant and van comycin resistant strains, and is active also against some Gram-negative bacteria such as M. catharralis, Neisseria species and H. influenzae and Mycobacteria.Jedinjenje formule(SEQ ID NO:2) u kome je X odabrano iz grupe koju čine: H, F, Cl, Br i J；pri čemu su Y1,Y2, Y3, Y4 i Y5 nezavisno odabrani iz grupe, koju čine: S, S-O-, S=O, O- -S=O i O=S=O；i pri čemu su R1, R2, R3, R4, R5, R6, R7 i R8 nezavisno odabrani iz grupe koju čine: H, OH, alkil i aril, uz uslov da najmanje jedan od Y1, Y2, Y3, Y4 i Y5 nije S.Prijava sadrži još 17 patentnih zahteva.
