Identification of Staphylococcus Spp. Isolated From Food by Two Methods

Abstract

One hundred and ninety-three staphylococcal strains were isolated from samples of alaska pollock meat (Theragra chalcogramma), atlantic mackerel meat (Scomber scombrus), atlantic herring meat (Clupea harengus), and femoral muscle samples of the wild pheasants (Phasianus colchicus), wild rabbits (Oryctolagus cuniculus) and bryndza cheese. Phenotypic manifestations typical of individual staphylococcal species were detected in these isolates. Species identification was also performed by matrix-assisted-laser-desorption-ionization-mass-spectrometry on the basis of which 5 species of staphylococci were determined: S. aureus, S. epidermidis, S. capitis, S. haemolyticus, S. warneri. Subsequently, the presence of the 16S rDNA gene was confirmed by PCR assay; a specific sequence for S. aureus species; putative transcriptional regulator gene serp0107, a specific sequence of the sodA gene was used to identify S. epidermidis and to identify S. warneri, S. haemolyticus, S. capitis species. When comparing the results of identification by PCR assay and matrix-assisted-laser-desorption-ionization-mass-spectrometry, the identification at the genus level was identical in all cases (100%). However, the discrepancies in results were confirmed at the species level, where congruence for identification of isolates by PCR assay and matrix-assisted-laser-desorption-ionization-mass-spectrometry was only 80%. For these isolates, the score value ranged from 1.953 to 2.564.