Evaluation of Antimicrobial Peptides Against Pseudomonas aeruginosa in Various Media
Technical Report,01 Jul 2014,31 May 2018
Naval Medical Research Unit San Antonio Fort Sam Houston United States
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Multidrug resistant MDR bacteria, and nosocomial infections are increasingly common, with military personnel and the general population. However, few novel antibiotics are currently in development to combat them. The use of antimicrobial peptides AMPs is one new avenue currently under development to address the global need for new antibacterial therapies. On the other hand, as experiments use varying growth conditions, target species or strains, and doses, research consensus on AMP efficacy is limited. The purpose of this study was to evaluate the effect of bacterial growth conditions on AMP antibacterial activity, and set a reasonable standard for objective comparison between AMPs. Three AMPs were selected and tested against Pseudomonas aeruginosa, an opportunistic pathogen of international concern. AMP selection was based on their peptide size, mode of action, efficacy, and cytotoxicity. This evaluation was designed to balance antibacterial and antibiofilm activity against cytotoxicity levels. Standardized antibacterial activity assays were conducted with three selected AMPs against four varieties of P. aeruginosa two laboratory strains and two MDR clinical isolates. Bacteria were exposed to various growth conditions two different minimal and two different complete media. AMPs were also tested for antibiofilm activity and cytotoxicity in human gingival epithelium progenitor cells. Antibacterial and antibiofilm efficacies varied by over 100-fold with target bacterial strain and growth conditions. AMP 1018 disrupted biofilms at low concentrations while K6L9 was effective against both laboratory strains and biofilms. KSL-W showed generally better antibacterial activity but was less effective in disrupting biofilms than 1018. Culture medium had a larger impact on AMP efficacy than strain identity, including MDR status. Changes in bacterial growth conditions have large effects on AMP efficacy.