IDENTIFICATION OF BACILLUS STRAINS ISOLATED FROM MILK AND CREAM WITH CLASSICAL AND NUCLEIC-ACID HYBRIDIZATION METHODS

A total of 529 bacterial strains have been isolated from milk and crea m sampled at different sites in a dairy production plant under conditi ons selective for aerobic sporeforming bacteria. Identification with c lassical methods based on morphological, physiological and biochemical criteria showed Bacillus licheniformis to be the most frequently occu rring Bacillus sp. The investigation also revealed 62 unidentified str ains. Classical identification methods were time consuming (3-7 d), la cked specificity and-because of their dependence on phenotypic gene ex pression -sometimes produced ambiguous results. Consequently, a colony hybridization method developed for the identification of B. lichenifo rmis strains and using nonradioactive labelled 23S rRNA targeted oligo nucleotide probes was also used. Identification of B. licheniformis wi th both classical and hybridization methods revealed diverging identif ication results for 70 strains.