DIRECT DETECTION OF LACTOCOCCAL BACTERIOPHAGES IN CHEESE WHEY USING DNA PROBES

We have designed a new method for the rapid detection of lactococcal phage directly in milk samples. The method was based on a dot blot analysis and did not require a biological assay with sensitive indicator strains. Culture media or whey permeate samples containing phage were spotted directly onto a nylon membrane and the phage were lysed in situ prior to hybridization. For skim milk, whole milk and whey samples, the, samples were first treated with 50 mM EDTA, 20% Triton X-100 and heated at 60-degrees-C for 5 min, prior to spotting on the membrane. The detection limit was approximately between 10(5) and 10(7) pfu/spot. A large number of samples could be processed simultaneously and the results were obtained within 24 h.