Identification by 16S-23S rDNA intergenic region amplification, genotypic and phenotypic clustering of Staphylococcus xylosus strains from dry sausages.

Aims: To ascertain the identification and typing of the Gram-positive, coagulase-negative cocci present in 'Salsiccia Sotto Sugna', an Italian artisanal sausage. Methods and Results: Fifty-one strains were isolated and genotypically identified by amplification of the 16S-23S rDNA intergenic region with universal primers. Most isolates were identified as Staphylococcus xylosus and one strain as Staph. condimenti. Isolates were clustered by numerical analysis of both RAPD (Random Amplified Polymorphic DNA) PCR profiles and physiological characters. Genotypic clustering allowed the separation of strains showing nitrate reduction and amino acid decarboxylase activities. Phenotypic clustering distinguished strains isolated at diverse ripening stages. Conclusions: The predominance of Staph. xylosus in Italian dry sausages was confirmed. Genotypic similarities related to the possession of single phenotypic traits. Significance and Impact of the Study: In this study, a rapid method of Staphylococcus and Kocuria species distinction was proposed. The suitability of RAPD PCR to discriminate strains of Staph. xylosus with technologically relevant activities was reported.