A STUDY OF THE MICROBIOLOGICAL STATUS OF IRISH FARMHOUSE CHEESES WITHEMPHASIS ON SELECTED PATHOGENIC AND SPOILAGE MICROORGANISMS

Ninety-six 25 g samples from 25 Irish farmhouse cheeses, two Irish non -farmhouse cheeses and four foreign cheeses were evaluated for the pre sence of a variety of micro-organisms, namely, coliforms, faecal strep tococci, Staphylococcus aureus, yeasts, moulds, salmonellas and shigel las. Seventeen cheeses, i.e. the soft and semi-soft types, were examin ed for Listeria monocytogenes. Most of the farmhouse cheeses are curre ntly manufactured from raw milk, but some producers now use heat-treat ed milk. The incidence of coliforms and faecal coliforms was higher in soft, semi-soft and semi-hard cheeses than in hard types. High levels of contamination by faecal streptococci and non-pathogenic (coagulase -negative Staph. aureus prevailed in a high proportion of the cheeses. Pathogenic (coagulase-positive) staphylococci, however, were also iso lated from 50% of the cheeses, some of which were manufactured from pa steurized milk. Yeasts were found mainly in unpasteurized varieties, e specially in the category of soft cheeses. Moulds were isolated from f ive non-mould-ripened cheeses, as well as from mould-ripened varieties . Salmonellas, shigellas and Listeria monocytogenes were not detected after direct enrichment.