Study of enterococci and micrococci isolated throughout manufacture and ripening of San Simón cheese

Abstract

The aim of this study was the enumeration and identification of enterococci and Micrococcaceae throughout the manufacture and ripening of five batches of San Simón cheese. The highest counts on mannitol salt agar (MSA) were obtained after 1 week of ripening in the samples taken from the core of the cheese and after 2 weeks in those from the surface. The percentage of strains that belonged to the Micrococcaceae was only 18·89% of the isolates from the core portion of the cheese and 35% with respect to those isolated on the surface. The predominant species both in the core and on the surface of the cheese was Staphylococcus sciuri. Of the strains isolated in MSA from the milk, curd and core of the cheese, 38·89% were from the genus Enterococcus and 26·25% of those isolated in the superficial portion were Enterococcus faecalis in both cases. During ripening the percentage ofMicrococcaceae decreased, while the percentage of enterococci increased, a phenomenon which can be related to the ability of enterococci to adapt to the conditions present in cheese during ripening. The maximum counts were obtained on kanamycin aesculin azide (KAA) agar after 1 week of ripening, both in the core and on the surface of the cheese, and were fairly stable during the whole ripening. Enterococci isolated in KAA agar constituted 79·63% of the isolates from the milk, curd and core of the cheese (and 90% with respect to the isolates taken from the surface), with predominance in both portions of the species E. faecalis.