OCCURRENCE OF PROPIONIBACTERIUM-FREUDENREICHII BACTERIOPHAGES IN SWISS CHEESE

We isolated bacteriophages active against Propionibacterium freudenrei chii from 16 of 32 Swiss cheese samples. Bacteriophage concentrations ranged from 14 to 7 x 10(5) PFU/g, depending on the sample and the sen sitive strain used for detection. Only a few strains, 8 of the 44 stra ins of P. freudenreichii in our collection, were sensitive. We observe d that multiplication of bacteriophages occurred in the cheese loaf du ring multiplication of propionibacteria in a warm curing room, but it seems that these bacteriophages have no adverse effect on the developm ent of the propionic flora. We also found that sensitive cells, origin ating from either the starter or the cheese-making milk, were present at a high level (10(9) CFU/g) in the cheese.