Characterization of the Synergistic Antibacterial Effect of Verapamil on Bacterial Isolates From Cancer Patients

Multidrug-resistant (MDR) bacteria represent a significant global health challenge, particularly among immunocompromised populations such as cancer patients undergoing chemotherapy. These patients are highly susceptible to severe infections due to weakened immune defenses, often necessitating the use of broad-spectrum or combination antibiotic therapy. Combination regimens may enhance treatment efficacy through synergistic effects, helping to overcome bacterial resistance mechanisms and improve clinical outcomes. In recent years, there has been growing interest in the use of non-antibiotic drugs as adjunctive agents to enhance antimicrobial activity. These agents, often referred to as antibiotic adjuvants or resistance modifiers, may improve antibiotic effectiveness through mechanisms such as inhibition of bacterial efflux pumps, disruption of biofilm formation, or interference with resistance pathways. Verapamil, a widely used calcium channel blocker, has demonstrated potential antimicrobial and resistance-modifying properties. Experimental evidence suggests that verapamil can inhibit bacterial efflux pumps, thereby increasing intracellular concentrations of antibiotics and enhancing their activity against resistant organisms. This study aims to evaluate the in vitro synergistic antibacterial activity of verapamil in combination with selected antibiotics against MDR, extensively drug-resistant (XDR), and pandrug-resistant (PDR) bacterial isolates obtained from cancer patients. Standard microbiological methods will be used to determine antimicrobial susceptibility and minimum inhibitory concentrations, while combination effects will be assessed using established synergy testing approaches. The findings of this study may contribute to identifying novel, cost-effective strategies to combat antimicrobial resistance through drug repurposing and optimization of existing antibiotic therapies.