Comparative Evaluation of Ciprofloxacin and Azithromycin Against Biofilm Forming Escherichia coli

Abstract

Background and Objective: Escherichia coli biofilm-associated infections pose a major therapeutic challenge due to the protective nature of the Extracellular Polymeric Substance (EPS) matrix, which enhances bacterial resistance to antibiotics and host immune responses. These biofilms are responsible for recurrent urinary tract infections (UTIs) and infections associated with indwelling medical devices. The present study aimed to compare the antimicrobial efficacy of ciprofloxacin and azithromycin against E. coli biofilms and to explore potential synergistic effects between the two antibiotics.

Materials and Methods: Clinical isolates of E. coli were obtained and tested for biofilm formation using standard culture techniques. The antimicrobial susceptibility of the isolates was evaluated using the Kirby-Bauer disc diffusion method. Ciprofloxacin and azithromycin, representing fluoroquinolone and macrolide antibiotic classes respectively, were tested individually and in combination to assess their inhibitory effects. Zones of inhibition were measured to determine antibiotic efficacy and potential synergism between the two agents.

Results: Ciprofloxacin exhibited significant antibacterial activity against planktonic E. coli but showed reduced efficacy against biofilm-embedded bacteria, likely due to restricted antibiotic penetration and low bacterial metabolic activity within the biofilm matrix. Azithromycin demonstrated moderate inhibition of E. coli biofilms, attributed to its interference with quorum sensing and disruption of biofilm integrity. When used in combination, ciprofloxacin and azithromycin showed enhanced antibacterial activity, reflected by increased zones of inhibition, indicating a synergistic interaction.

Conclusion: The findings highlight the limited effectiveness of ciprofloxacin alone against E. coli biofilms and emphasize the potential of azithromycin to enhance its efficacy through combined action. This study supports a multifaceted therapeutic approach for managing biofilm-associated infections, incorporating combination antibiotic therapies and biofilm-targeting strategies. Further research into antibiofilm agents and molecular mechanisms of resistance is essential for developing effective interventions against persistent E. coli infections and mitigating the growing threat of antimicrobial resistance.