Pseudomonas aeruginosa has eventually developed resistance against
flomoxef sodium,
isepamicin and
cefpiramide. Therefore, in this study, the antibacterial activity and synergistic effects of the amphipathic-derived P5-18mer
antimicrobial peptide were tested against pathogens associated with
cholelithiasis that have developed resistance against commonly used
antibiotics. The results were then compared with the activities of the amphipathic-derived
peptide, P5-18mer,
melittin and common
antibiotics. Growth inhibition of planktonic bacteria was tested using the National Committee for Clinical Laboratory Standards (NCCLS). The bactericidal activity of the
antimicrobial peptides was measured using time-kill curves. Synergistic effects were evaluated by testing the effects of P5-18mer alone and in combination with
flomoxef sodium,
isepamicin or
cefpiramide at 0.5xMIC.
P5-18mer peptide displayed strong activity against pathogens and
flomoxef sodium,
isepamicin and
cefpiramide-resistant bacteria cell lines obtained from a patient with
gallstones; however, it did not exert cytotoxicity against the human keratinocyte HaCat cell line. In addition, the results of time-kill curves indicated that
P5-18mer peptide exerted bactericidal activity against four strains of P. aeruginosa. Finally, the use of P5-18mer and
antibiotics exerted synergistic effects against cell lines that were resistant to commonly used
antibiotics. These results indicate that this class of
peptides has a rapid microbicidal effect on
flomoxef sodium,
isepamicin and
cefpiramide-resistant strains of P. aeruginosa. Therefore, these
peptides may be used as a lead
drug for the treatment of acquired pathogens from patients with
cholelithiasis who are affected with
antibiotic-resistant bacteria.