Levofloxacin and indolicidin for combination antimicrobial therapy.

Despite the increasing need for antibiotics to fight infectious diseases, fewer new antibiotics are available on the market. Unfortunately, developing a new class of antibiotics is associated with high commercial risk. Therefore, modification or combination of existing antibiotics to improve their efficacy is a promising strategy. Herein, we conjugated the antibiotic, levofloxacin, with two peptides, i.e. an antimicrobial peptide indolicidin and a cell penetrating peptide (TAT). Glycolic acid and glycine linkers were used between levofloxacin and peptides. We developed an optimized condition for coupling of levofloxacin via its carboxylic group to glycolic acid using solid phase peptide synthesis (SPPS). Antibacterial and haemolytic assays were carried out on the conjugates and only the levofloxacin-indolicidin conjugate demonstrated moderate antibacterial activity. Interestingly, physical mixture of levofloxacin and indolicidin showed improvement in the activity against Gram-positive bacteria.