The study found that mixing the natural antimicrobial peptide LL-37 with lab-made compounds called ceragenins (CSA-13 and CSA-131) kills drug‑resistant E. coli in the bladder better than LL-37 alone. This suggests a possible new way to boost the body's own defenses against stubborn urinary infections.

Urinary tract infections (UTIs) are one of the most common bacterial infections. High recurrence rates and the increasing antibiotic resistance among uropathogens constitute a large social and economic problem in current public health. We assumed that combination of treatment that includes the administration ceragenins (CSAs), will reinforce the effect of antimicrobial LL-37 peptide continuously produced by urinary tract epithelial cells. Such treatment might be an innovative approach to enhance innate antibacterial activity against multidrug-resistant E. coli. Antibacterial activity measured using killing assays. Biofilm formation was assessed using crystal violet staining. Viability of bacteria and bladder epithelial cells subjected to incubation with tested agents was determined using MTT assays. We investigated the effects of chosen molecules, both alone and in combinations against four clinical strains of E. coli, obtained from patients diagnosed with recurrent UTI. We observed that the LL-37 peptide, whose concentration increases at sites of urinary infection, exerts increased bactericidal effect against E. coli when combined with ceragenins CSA-13 and CSA-131. We suggest that the employment of combination of natural peptide LL-37 with synthetic analogs might be a potential solution to treat urinary tract infections caused by drug-resistant bacteria.