The invention related to a antimicrobial agent being a Lactobacillus reuteri DAN080 culture, a partially inactivated L. reuteri DAN080 culture, liquid supernatant of L. reuteri DAN080 culture, concentrated supernatant of L. reuteri DAN080 culture, and dried supernatant of L. reuteri DAN080 culture, for the prophylaxis and treatment of medical conditions developing as a result of infections caused by bacteria, fungi, and other pathogens of the gastrointestinal tract, body surface, and other systems, such as urogenital system, respiratory system, in vertebrates. An antimicrobial agent selected from the group comprising the whole L. reuteri DAN080 culture, liquid supernatant, concentrated supernatant, and dried supernatant obtained from L. reuteri DAN080 culture and from mixed bacterial cultures, containing L . reuteri DAN080, and liquid supernatants, concentrated supernatants and dried supernatants obtained from the cultures of prokaryotic and eukaryotic recombinants, and the whole cultures of prokaryotic and eukaryotic recombinants, in which and/or from which genes are utilized, which genes provide specific modulatory, inhibitory, and homeostatic activity with respect to H. pylori and other bacteria； proteins/oligopeptides/peptides of molecular weight of approximately: 150 and/or 141 and/or 115 and/or 95 and/or 90 and/or 86 and/or 83 and/or 77 and/or 71 and/or 63 and/or 59 and/or 56 and/or 49 and/or 46 and/or 43 and/or 39 and/or 34 and/or 32 and/or 30 and/or 22 kD, or lower, purified/isolated from liquid, concentrated, dried supernatants, obtained from L. reuteri DAN080, and purified/isolated from the whole L. reuteri DAN080 cultures, and from other mixed bacterial cultures, which included L. reuteri DAN080, and from purified or isolated cultures of prokaryotic and eukaryoticrecombinants, in which and/or from which genes are utilized, which genes provide specific modulatory, inhibitory, and homeostatic activity with respect to H. pylori an
