Probiotic characterization of Lactobacillus helveticus BGTRM7-58 from Khiki cheese: safety, antimicrobial activity, antioxidant capacity, and anti-biofilm effects against Staphylococcus aureus.

Traditional Iranian cheeses, especially "Khiki cheese," represent valuable sources of indigenous lactic acid bacteria with potential probiotic properties. This study evaluated the probiotic attributes, safety profile, antimicrobial efficacy, antioxidant capacity, and anti-biofilm activity of Lactobacillus helveticus BGTRM7-58, a strain isolated from Khiki cheese. The strain demonstrated considerable anti-adhesion capability against Staphylococcus aureus. The cell-free supernatant (CFS) exhibited potent antimicrobial activity, displaying a minimum inhibitory concentration (MIC) of 15.625 mg/mL against S. aureus. Furthermore, the CFS inhibited biofilm formation by 87% at 4× MIC and disrupted pre-established mature biofilms by 89% at the same concentration. In vitro cytotoxicity assessment revealed dose-dependent antiproliferative effects against cancer cell lines. Quantitative real-time PCR analysis indicated significant downregulation of key staphylococcal virulence genes, most notably a 47% reduction in agr expression. The strain also exhibited substantial antioxidant activity, scavenging 68.67%, 71.75% of DPPH and ABTS radicals, respectively. Comprehensive safety evaluation confirmed the absence of hemolytic and DNase activities, no production of biogenic amines, and susceptibility to clinically relevant antibiotics. Taken together, these findings indicate that L. helveticus BGTRM7-58 fulfills the fundamental criteria for a safe and functional probiotic strain, highlighting its potential for application in functional food formulations and strategies aimed at controlling biofilm-associated infections.