Detection of biofilm formation, virulence factor genes, antibiotic-resistance, adherence properties, and some beneficial properties of cheese origin S. infantarius, S. gallolyticus, and S. lutetiensis strains belonging to the S. bovis/S. equinus complex

Abstract

This study was conducted to determine whether the potential health benefits of cheese-related Streptococcus (S.) infantarius, S. gallolyticus, and S. lutetiensis strains taxonomically belonging to the S. bovis/S. equinus complex (SBSEC) could be addressed without safety concern. All strains showed antagonistic effect against Staphylococcus (S.) aureus ATCC 25923 and produced a high amount of exopolysaccharide (293.48–365.95 μg/mL). Moreover, they presented high hydrophobicity towards n-hexadecane and xylene. The highest cholesterol assimilation (13.95–19.30%) and β-galactosidase activity (35.17–43.33 MU) were determined in isolates 930 and 120. Besides, all isolates neither showed hemolytic activity nor harbored virulence genes (asa1, gelE, cylA, cylB, epfSTR, hylSTR, mrpSTR, slySTR, bay046STR). However, only isolate 937 harbored the arcSTR virulence gene. Besides, isolates 937 and 120 were observed to degrade arginine. All isolates, except for isolate 937, were susceptible to penicillin, ampicillin, chloramphenicol, and vancomycin. All isolates had biofilm-forming capability. Considering all benefits and safety features, isolate 930 can be suggested for further in vivo and in situ investigations. This study does not claim that the SBSEC group bacteria, which are associated with many diseases, are actually beneficial, but only supports the view that clinical origin SBSEC group bacteria can be evaluated differently from those isolated from fermented products.