Lacticin 3147, produced by a lactococcal isolate from Irish Kefir grains used in the manufacture of buttermilk, is effective against a wide spectrum of gram-positive bacteria (McAuliffe et al., 1998; Ryan et al., 1998; McAuliffe et al., 1999). Unlike nisin lacticin 3147 is effective at neutral pH. The genetic determinants of the lacticin are located on a conjugative plasmid and have recently been transferred to strains used in the manufacture of Cheddar cheese (Ryan et al., 1996). The resulting cheeses were of normal composition except that they contained no non-starter lactic acid bacteria (NSLAB). This application of lacticin 3147 will prove very useful in studying the role of these latter bacteria in developing flavour and other characteristics in cheeses.