MONITORING AND CHARACTERIZATION OF LACTOCOCCAL BACTERIOPHAGES IN A DAIRY PLANT

During a 6-months period, phage monitoring was performed in the quarg production section of a dairy factory practising rotation of 5 undefin ed mixed-strain starter cultures. A wide distribution of virulent phag es was shown in samples from the bulk starters, from wheys and those d rawn from the air. Phage load was up to 3x10(9) plaque forming units ( pfu) per ml whey and up to 6x10(6) pfu per m3 air from the separator r oom. A significant shift in phage population occurred during the cours e of this study: While small isometric-headed phages were found in the beginning, prolate-headed phages appeared later upon introduction of culture C into the rotation scheme. This culture was not related to th e other 4 cultures with respect to phage sensitivity. The latter were all phage-related and only partly suitable for culture rotation.