Safety assessment of selected Staphylococcus carnosus strains with regard to their application as meat starter culture

• The prevalence of pathogenicity and virulence factors in Staphylococcus carnosus was studied.
• 41% of the strains cannot be applied as starter cultures based on the QPS concept.
• Virulence and pathogenicity determinants are strain- and not subspecies-specific.
• Individual testing of strains is recommended before the application in food.

In this study, 39 different Staphylococcus carnosus strains were analysed for virulence and pathogenicity determinants with regard to their application as starter cultures for the fermentation of meat products. Therefore, the Qualified Presumption of Safety concept of the European Food Safety Authority was used as a guideline to estimate their potential health risk for consumers, with emphasis on antibiotic resistance, presence of toxin genes and production of biogenic amines. The resistance against 17 antibiotics was analysed with an agar disc diffusion test according to the Clinical and Laboratory Standards Institute. Ten strains were resistant or intermediate resistant against cefotaxime, chloramphenicol, oxacillin or trimethoprim/sulfamethoxazole. Of these, only two strains were resistant to more than one antibiotic. None of the tested strains was PCR-positive with primers targeting the staphylococcal enterotoxin genes (sea-see, seh), the exfoliative toxin gene (eta) or the toxic shock syndrome toxin gene (tst-1). Two strains showed β-haemolysis on human blood agar plates and were excluded from the study. The remaining 22 antibiotic-sensitive and non-toxigenic S. carnosus strains were tested for the production of biogenic amines by HPLC-analysis. None of the strains produced cadaverine, putrescine and histamine under the experimental conditions used, but 12 strains produced phenethylamine in concentrations ranging between 2.6 and 15.0 μg/mL. The results of this study indicate that safety risks, such as antibiotic resistance and biogenic amine production, are quite common among strains of the species S. carnosus. Consequently, each strain should be analysed individually before it is applied as starter culture in meat products.