Bicarinalin Enhances the Antibacterial Activity of Levofloxacin and Clarithromycin Against Helicobacter pylori.

Background/Objectives:Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the human stomach and causes various gastrointestinal diseases. Although antibiotic therapy is the most effective method for its eradication, the increasing prevalence of antibiotic resistance has made treatment increasingly challenging in recent years. In this study, the antimicrobial activity, synergistic effects with antibiotics, and mechanisms of action of Bicarinalin, an antimicrobial peptide (AMP) derived from the venom of Tetramorium bicarinatum, were investigated against H. pylori. Methods: To determine the antibacterial activity of Bicarinalin, a well diffusion assay was performed, yielding an inhibition zone of 18.3 mm at a concentration of 32 µg/mL for ATCC strain. MIC99 values were determined by microdilution tests as 4.8 μg/mL for the reference strain. The enhancement of the antimicrobial potential of levofloxacin and clarithromycin when administered together with Bicarinalin has been demonstrated using the well diffusion method. Results: Inhibition zones increased from 14.2 mm to 20 mm for levofloxacin and from 7.3 mm to 16 mm for clarithromycin. This study is the first to identify DNA and protein leakage caused by Bicarinalin in H. pylori. Intracellular protein and DNA leakage were measured, with protein and DNA levels released into the extracellular environment determined as 33.25% and 55.10%, respectively, following Bicarinalin treatment. Furthermore, to investigate its effect on membrane damage, scanning electron microscopy (SEM) was performed, revealing disrupted cell membrane structures, penetration between cells, and severe deterioration of morphological integrity. Conclusions: This study has demonstrated for the first time that, when administered concomitantly, Bicarinalin enhances the antimicrobial activities of levofloxacin and clarithromycin. This highlights its potential as an adjunctive treatment for H. pylori alongside existing drugs.