Antibiotic activity of antimicrobial peptide against Pseudomonads isolated from a patient with gallstones.

We investigated the in vitro antibiotic activity of the 19-amino acid antimicrobial peptide HP (2-20), derived from the N-terminus of Helicobacter pylori Ribosomal Protein L1 (RPL1), against antibiotic susceptible and resistant pathogens from a patient with gallstones. HP (2-20) was active against antibiotic-susceptible and antibiotic-resistant clinical isolates of pathogens from a patient with gallstones, but this peptide showed no hemolytic activity against normal human erythrocytes. HP (2-20) acted synergistically with ciprofloxacin against pathogenic bacteria. Fluorescence activated flow cytometry revealed that the effect of HP (2-20) was dependent on energy and salt concentration. In addition, scanning electron microscopy showed that HP (2-20) caused significant morphological alterations to the cell surface of pathogens. Using 16S rDNA sequences, we found that isolates from bile were 100% homologous to Pseudomonas aeruginosa. These findings suggest that HP (2-20) may be useful clinically as an antibiotic against acquired pathogens from patients with gallstones and against pathogens resistant to other antibiotics.