A Qualified Presumption of Safety approach for the safety assessment of Grana Padano whey starters

A Qualified Presumption of Safety (QPS) approach was applied to dominant lactic acid bacteria (LAB) associated with Grana Padano cheese whey starters. Thirty-two strains belonging to Lactobacillus helveticus, Lactobacillus delbrueckii subsp. lactis, Streptococcus thermophilus, and Lactobacillus fermentum, and representing the overall genotypic LAB diversity associated with 24 previously collected whey starters [Rossetti, L., Fornasari, M.E., Gatti, M., Lazzi, C., Neviani, E., Giraffa, G., 2008. Grana Padano cheese whey starters: microbial composition and strain distribution. International Journal of Food Microbiology 127, 168–171], were analyzed. All L. helveticus, L. delbrueckii subsp. lactis, and S. thermophilus isolates were susceptible to four (i.e. vancomycin, gentamicin, tetracycline, and erythromycin) of the clinically most relevant antibiotics. One L. fermentum strain displayed phenotypic resistance to tetracycline (TetR), with MIC of 32 µg/ml, and gentamycin (GmR), with MIC of 32 µg/ml. PCR was applied to this strain to test the presence of genes tet(L), tet(M), tet(S), and aac(6ʹ)-aph(2ʹ)-Ia, which are involved in horizontal transfer of TetR and GmR, respectively but no detectable amplification products were observed. According to QPS criteria, we conclude that Grana cheese whey starters do not present particular safety concerns.