METFORMIN ANTIBACTERIAL AND ANTI-VIRULENCE ACTIVITIES AGAINST HELICOBACTER PYLORI

Abstract

Introduction: Helicobacter pylori (H. pylori) infection is highly prevalent worldwide and is associated with multiple gastroduodenal pathologies, including gastric cancer. The increasing drug resistance among H. pylori limits available treatment options. To overcome this challenge, drug repurposing and the use of current medications as adjuvant therapies have emerged as a valuable alternative strategy. Metformin is a commonly prescribed anti-diabetic drug for type 2 diabetes mellitus (T2DM); it has been shown to have antibacterial properties. This study aimed to investigate metformin’s antimicrobial activity against H. pylori, its virulence factors and evaluate its potential dual synergy with each of the six antibiotics commonly used in the treatment of H. pylori infections. Methods: The antibacterial effect of metformin on H. pylori was evaluated using both clinical isolates and reference laboratory strains by detecting the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Furthermore, a checkerboard assay was conducted to assess the combined effect of metformin with six antibiotics used to treat H. pylori infections (levofloxacin, metronidazole, tetracycline, amoxicillin, rifampicin, and clarithromycin). Additionally, phenotypic evaluation of its antibiofilm and antiurease activities followed by molecular detection for a panel of virulence genes’ expression using real-time PCR. Results: Metformin showed antibacterial activity against H. pylori with MIC values ranging between 6.38 and 9.75 mM (1131-1615 µg/mL). MIC/MBC ratios and time-kill study suggested a bactericidal effect against the tested H. pylori strains. Moreover, the Fractional Inhibitory Concentration Index (FICI) values support metformin additive effect (FICI values 0.52-1.0), without synergistic or antagonistic interactions. Metformin expressed a profound biofilm suppression with comprehensive downregulation for the studied genes, marked by virB4 gene reduced expression. Conclusion: The additive effect and the bactericidal activity of metformin suggest a potential clinical relevance for diabetic patients already receiving this medication. Furthermore, the observed anti-virulence activity may potentiate metformin’s role as an adjuvant. However, comprehensive studies are needed to further evaluate the safety and efficacy using in vivo, preclinical, and clinical trials.