Inhibition of ruminal staphylococci and enterococci by nisin in vitro.

A collection of 59 ureolytic and lactic acid-producing ruminal staphylococci and enterococci, isolates from domestic and wild ruminants, were tested for sensitivity or resistance to lantibiotic nisin. All strains tested were sensitive with zones of inhibition, around wells containing 250 micrograms nisin, from 6 to 26 mm. 74.6% of isolates had zones of inhibition more than 10 mm and 11.1% more than 20 mm. Nisin was more effective against enterococci than staphylococci. Sensitivity of ruminal isolates to nisin may be used to control bacterial growth during the colonization of the rumen or to study the role of antibacterial activity in microbial interactions. Results obtained can be also used in experiments on gnotobiotic animals.