Taxonomic characterization of coagulase-negative staphylococci in ripening flora from traditional French cheeses

Various methods were used to identify 145 staphylococcal strains isolated from 25 traditional types of cheeses. With the biochemical micromethod rapid gallery system. ATE 32 Staph, only 33% of the strains could be identified. All the strains unidentified by API system (98 strains) were subjected to 35 conventional biochemical and physiological tests according to the Devriese's identification scheme (1985). The results were then analyzed by a numerical method using the Sokal and Michener similarity coefficient and the 98 strains were distributed into 15 clusters at the similarity level of 60%. Of the 145 strains analyzed, 36% were identified using the association of two phenotypic methods and 26% were considered as atypical S. xylosus or S. equorum strains. An identification method based on analysis of the ribotypes was applied to 67 strains from the 15 taxa. The cellular DNA was cleaved by the HindIII and EcoRI restriction enzymes. The restriction fragments were separated by electrophoresis, blotted and probed with fluorescein labeled plasmid pBA2 containing a Bacillus subtilis gene encoding 16S rRNA. Sixty six of the 67 strains ribotyped (98.5%) gave typical known species patterns. In conclusion, 99.5% of the 145 staphylococcal cheese strains were identified. All chese strains belonged to the novobiocin-resistant CNS species and near 90% to S. equorum, S. vitulus and S. xylosus which are not widespread among human associated strains.