In vitro antagonistic effect of nisin on faecal enterococci and staphylococci

Enterococci and staphylococci, isolates from faecal samples of 46 different animals such as deer, chamois, European bison, zebra, camel, antelope, gazelle, horse, and piglets were treated by nisin (concentration 1 mg/ml). Only two strains (SX38 and EA163), isolates from the faeces of deer were not inhibited by nisin under in vitro conditions. It means 97.4% of target isolates were inhibited by nisin and 2.6% were resistant. The majority of microorganisms were inhibited by nisin under MIC 1.56-100 mug/ml. Twenty-two percent out of 77 isolates were inhibited by MIC of nisin 3.12 mug. Enterococcus sp. E6B strain was found the most sensitive (inhibition by MIC 1.56 mug of nisin). Although only a few staphylococci were tested, most of them were inhibited by nisin. Even though the effect of nisin on the individual species was not evaluated, its effect on the group of bacteria is already important. In general, the properties of nisin indicate a broad spectrum of its utilization.