Kefir's Hidden Arsenal: Examining the Effect of Lactobacilli Supernatant on Antibiotic Resistance Genes and Virulence in Salmonella Typhimurium

Salmonella, a prominent foodborne pathogen, poses significant health risks, causing both intestinal and extra-intestinal infections. Recognizing the potential of lactobacilli as probiotics due to their ability to produce substances inhibiting multidrug-resistant bacteria, this study aimed to assess antibiotic resistance, pathogenic gene frequency, antibacterial effects of lactobacillus supernatant from kefir, and its impact on resistance and pathogenicity gene expression.In Tehran hospitals, 150 isolates from 240 clinical samples were collected and identified as Salmonella Typhimurium using biochemical and serotype tests. Antibiotic sensitivity was assessed, and the frequencies of antibiotic resistance genes (tetA, tetB, and floR) and pathogenicity genes (sip, spvC, and invA) were investigated. Lactobacilli from kefir were isolated, and the minimum inhibitory concentration of lactobacillus supernatant was determined. The relationship between supernatant treatment and tetA and sip gene expression was examined using Real-time PCR.Results revealed 38% of strains as Salmonella Typhimurium serotype, displaying high resistance to ampicillin, tetracycline, and nitrofurantoin. Pathogenicity genes invA and sip exhibited high frequencies of 100% and 70.2%, respectively. Lactobacillus supernatant showed an MIC of 80 μg/ml, effectively reducing tetA and sip gene expression by 42.2% and 55.7%, respectively.In conclusion, the study underscores the high antibiotic resistance in Salmonella Typhimurium and suggests Meropenem, Trimethoprim Sulfamethoxazole, and Ampicillin-Sulbactam as effective treatments. Moreover, lactobacillus supernatant demonstrated significant potential against Salmonella Typhimurium, highlighting lactobacilli as promising probiotics. This health-oriented strategy presents a viable solution for treating Salmonella infections and preventing their spread.