Synergistic Effect of Antimicrobial Peptide LL-37 and Ciprofloxacin against Multidrug Resistant Pseudomonas aeruginosa Isolated from Burn Infections

Abstract

Pseudomonas aeruginosa is one of the most prevalent opportunistic bacteria, with a high activities rate in patients with burns and weakened immune systems. This study aimed to determine the inhibitory activity of the antimicrobial peptide LL-37 in combination with the antibiotic Ciprofloxacin against multidrug resistant isolates of Pseudomonas aeruginosa isolated from patients with burn infections. In this study, the checkerboard broth microdilution method was used to examine the antibacterial properties of the combination of LL-37 and Ciprofloxacin to determine the fractional inhibitory concentrations (FICs) at the concentrations (7.8-0.060 µg/ml) for selected eight multidrug resistant isolates. The results of synergism revealed that the concentrations with inhibitory activity for antimicrobial peptide LL-37 and ciprofloxacin were reduced to very low concentrations with FIC ranging from (0.0024-0.26 µg /ml). According to the synergistic effect, the MIC of LL-37 was reduced from 250 to 0.97 µg/ml for the isolate P1, while for the isolate P32 the MIC OF Ciprofloxacin was reduced from 1000 to 0.12 µg/ml. In conclusion, the current findings indicated that LL-37 and Ciprofloxacin combination was effective against multidrug-resistant Pseudomonas aeruginosa strains and suggested a new alternative option for burn infection treatment.