The ability of Listeria monocytogenes to grow at low temperatures and increase to
hazardous levels during storage of dairy products is of great concern to the dairy
industry. List. monocytogenes was detected in 3·6% of 774 cows' milk samples from
114 farms in Central Spain (Gaya et al. 1998). Ewes' and goats' milks produced in
Spain had contamination levels of 2·2 and 2·6% respectively (Rodríguez et al. 1994;
Gaya et al. 1996). List. monocytogenes may survive during the manufacture and
ripening of most cheese varieties, with higher risk in soft surface-ripened cheeses
owing to the rise in pH during ripening (Maisnier-Patin et al. 1992; Giraffa &
The efficacy with which actively growing bacteriocin-producing cultures inhibit
List. monocytogenes in some cheese varieties has been demonstrated. Nisin-producing
starters inhibited List. monocytogenes V7 in Camembert cheese (Maisnier-Patin et al.
1992) and List. innocua BL86/26 in raw ewes' milk Manchego cheese (Rodríguez et al.
1998). A lacticin 3147-producing starter culture (McAuliffe et al. 1999) reduced
List. monocytogenes Scott A levels in cottage cheese. Inoculation of milk with
enterocin AS-48-producing Enterococcus faecalis INIA 4 inhibited List. monocytogenes
strains Ohio and Scott A during the manufacture and ripening of Manchego cheese
(Nuñez et al. 1997).
Semi-hard cheese varieties from raw or pasteurized cows' milk mixed with
different proportions of ewes' and/or goats' milk represent ∼ 50% of Spanish cheese
production. The objective of the present work was to evaluate the antilisterial
activity of three bacteriocin-producing lactic acid bacteria strains isolated from milk
(Rodríguez et al. 2000) during the manufacture and ripening of a semi-hard cheese
manufactured from raw milk.