Synergistic Interaction of Salicylic Acid and Ciprofloxacin against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Serratia marcescens

Almonther Hershan

Background and Objective: Salicylic acid (SA), a notable member of phytoconstituents is known to possess remarkable antibacterial potential. The present investigation deals with the synergistic interaction of salicylic acid and ciprofloxacin (CIP), evaluating their antibacterial potential against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae and Serratia marcescens. Materials and Methods: The antibacterial potential of CIP, SA and a combination of CIP and SA was validated by MIC, MBC, broth checkerboard method, biofilm inhibition by crystal violet assay, membrane stability and time-kill kinetics. Expression levels of genetic markers such as lasB, MrkA and bsmB in P. aeruginosa, K. pneumoniae and S. marcescens, respectively were analyzed using PCR. Results: The MIC and MBC of E. coli and S. aureus of CIP was 5 μg/mL and for SA it was found to be 5 mg/mL for all the two microbes. Escherichia coli and Staphylococcus aureus tend to be resistant to SA. The combination of CIP and SA showed exceptional antibacterial capability toward P. aeruginosa, K. pneumoniae and S. marcescens. In the checkerboard assay, K. pneumoniae exhibited a partial synergistic effect with a FICI value of 0.502. Serratia marcescens and P. aeruginosa with FICI values of 0.49 and 0.48, respectively demonstrated synergistic action. The combination of CIP and SA effectively inhibits biofilm formation in P. aeruginosa, K. pneumoniae and S. marcescens in crystal violet assay. From membrane stability, it can be found that the combination of CIP and SA causes destabilization of the outer membrane of tested microbes. The results of the time-kill assay demonstrated that the combination of CIP and SA remarkably inhibited the proliferation of the tested bacterial population. The combination of CIP and SA exhibited significant downregulation of lasB, MrkA and bsmB. Conclusion: The combination of CIP and SA exerts enhanced antibacterial capability against tested microbes compared to CIP and SA alone. The antibacterial efficacy was greater against P. aeruginosa than against K. pneumoniae and S. marcescens.

View Fulltext Back