Use of conventional biochemical tests and analyses of ribotype patterns for classification of micrococci isolated from dairy products

Various methods were used to study 42 Gram-positive cocci belonging to the family of Micrococcaceae and isolated from dairy products. Only a few strai ns could be identified using the ATE 32 biochemical micromethod rapid galle ry system (API).; All strains were subjected to conventional biochemical te sts. The results were then analysed by a numerical method using the Sokal-M ichener similarity coefficient. The 42 strains were distributed into 10 clu sters at the Euclidean distance of 3.2. Most (75 %) of the isolates were id entified at the species level, but Micrococcus luteus could not be differen tiated from Mc. lylae within the,Micrococcus genus. An identification metho d based on the analysis of ribotype patterns was then applied to the isolat es and these were compared with the patterns of collection strains. Cellula r DNA was cleared by the restriction enzymes SacI and KpnI and probed with the perosidase-labelled 16S + 23S rRNA of Escherichia coli. Ribotype patter ns were analysed using a Dice coefficient and the unweighted pair group met hod using arithmetic averages, making dendrogram construction possible. Of the strains investigated, > 84 % were characterized to the species level. T he remaining strains were found to belong to the Arthrobacter group or were atypical,Micrococcus species. Of the isolates, 52% belonged to Micrococcus luteus, 17 % were identified as Kocuria varians and 7 % were assigned to t he Brachybacterium genus.