The effects of magainin 2, cecropin, mastoparan and melittin on Brucella abortus.

The effect of the alpha-helical polycationic peptides magainin 2, melittin, mastoparan and cecropin on the viability of Brucella abortus 544 (type species), B. abortus S19 (vaccine strain) and B. abortus S2308 (vaccine challenge strain) was determined. Rough mutants of these strains and the rough candidate vaccine strain B. abortus RB51 were also tested. S. typhimurium was used as a control. The peptides did not affect the viability of B. abortus smooth strains but some of the peptides affected viability of the rough strains. Magainin 2 at a concentration of 100 micrograms ml-1 did not reduce the viability of the rough B. abortus strains. Cecropin at a concentration of 15 micrograms ml-1 reduced the viability of the rough strains by approximately 10-fold. Mastoparan at a concentration of 50 micrograms ml-1 reduced the viability of the rough strains by approximately 100-fold. Melittin at a concentration of 20 micrograms ml-1 reduced the viability of the rough strains of B. abortus by approximately 1000-fold. The brucellae were significantly more resistant to all the cationic peptides than was S. typhimurium.