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The effects of magainin 2, cecropin, mastoparan and melittin on Brucella abortus
1USDA/ARS/NADC, Ames, IA 50010 USA. shalling@asrr.arsusda.gov
Abstract:
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.
Insights
Certain alpha-helical peptides show limited effect on smooth Brucella abortus strains but significantly reduce the viability of rough Brucella abortus mutants, indicating targeted antimicrobial potential. Salmonella Typhimurium was more susceptible.
Area of Science:
- Antimicrobial Peptides
- Bacteriology
- Immunology
Background:
- Brucella abortus causes significant zoonotic disease.
- Developing novel antimicrobials against Brucella is crucial.
- Alpha-helical polycationic peptides are a potential class of antimicrobials.
Purpose of the Study:
- To evaluate the in vitro efficacy of four alpha-helical peptides against various Brucella abortus strains.
- To compare the susceptibility of smooth and rough Brucella abortus strains to these peptides.
- To assess the potential of these peptides as targeted antimicrobials.
Main Methods:
- Testing magainin 2, melittin, mastoparan, and cecropin against smooth and rough Brucella abortus strains.
- Using Salmonella Typhimurium as a control organism.
- Determining peptide effects on bacterial viability at specific concentrations.
Main Results:
- Smooth Brucella abortus strains were resistant to all tested peptides.
- Rough Brucella abortus strains showed varying susceptibility: Cecropin (10-fold reduction), Mastoparan (100-fold reduction), Melittin (1000-fold reduction).
- Magainin 2 showed no significant effect on rough strains at the tested concentration. Brucellae were more resistant than S. Typhimurium.
Conclusions:
- Alpha-helical peptides exhibit differential activity against Brucella abortus, primarily affecting rough strains.
- Melittin and Mastoparan demonstrate potent bactericidal activity against rough Brucella abortus mutants.
- These findings suggest potential for developing peptide-based therapies targeting specific Brucella virulence factors or forms.