Violacein@Biogenic Ag system: synergistic antibacterial activity against Staphylococcus aureus.

Abstract

OBJECTIVES: To examine the synergistic antibacterial activity of violacein and silver nanoparticles (AgNPs) against ATCC bacteria, Staphylococcus aureus, Escherichia coli and two bacteria isolated from bovine mastitis. METHODS: Violacein from Chromobacterium violaceum and biogenic AgNPs from Fusarium oxysporum were evaluated in antimicrobial tests. RESULTS: E. coli isolates were not inhibited by violacein at concentrations up to 400 μM and they showed sensitivity for AgNPs between 62.5 and 250 μM. Staphylococcus aureus showed sensitivity to violacein with MIC of 200 μM, and the MIC with AgNPs between 250 μM and 125 μM. It was also tested the association between the two compounds through a concentration gradient and was observed the reduction of the MIC in the combination for both strains. CONCLUSION: The bactericidal effect of violacein against S. aureus was better when combined with AgNPs (synergistic).