Inactivation of food-borne pathogens with magainin peptides

The antimicrobial activity of magainin 2 (mag 2) and magainin 2 amide (mag 2 amide) was determined for 13 pathogenic bacterial test strains associated with food-borne disease. Magainin 2 (100 mu g/ml) initially inhibited the growth of some of the test strains, but recovery of the cells occurred between the 5th and 24th h of exposure to the peptide. Of the 13 bacterial strains tested, Salmonella heidelberg 3432-2 demonstrated the greatest recovery (from an initial reduction of similar to 7 log cycles). Magainin 2 amide exhibited greater inactivation across all bacterial test strains compared to mag 2. After 24 h of exposure, all 13 test strains were completely inactivated with log(10) reductions in the cell population exceeding 8.7. The minimal inhibitory concentration of mag 2 amide (total inactivation after 24 h of exposure to mag 2 amide) was determined for the 13 test strains and ranged from <3 mu g/ml to 50 mu g/ml. At 4 degrees and 20 degrees C, mag 2 amide exhibited less bactericidal activity than at 37 degrees C for the organisms tested. While the addition of bovine serum albumin to the inactivation assay medium at 37 degrees C reduced the bactericidal activity of mag 2 amide against the test strains, reductions in cell population still exceeded 3 log cycles.