Atividade antagonista de extrato intracelular obtido de Fusobacterium necrophorum: modo de ação e caracterização bioquímica

Abstract

Fusobacterium necrophorum is considered as a member of the indigenous microbiota of the oral cavity, intestines and genitourinary tract of animals and is associated with the etiopathogenesis of several human and animal diseases, expressing a range of virulence factors for both. The ability to produce antagonistic substances that inhibit the growth or kill competing bacteria is considered an important virulence trait. Among them bacteriocins, a heterogeneous group of peptide antibacterial compounds, should be highlighted. Our group has demonstrated for the first time the production of proteinaceous antagonistic substances by F. necrophorum active against bacteria of other species. This study aimed to contribute to the biochemical and molecular understanding of these molecules. The intracellular extract obtained from a F. necrophorum culture precipitated at 50% ammonium sulfate saturation (C50) was able to kill the indicator strain (Peptostreptococcus anaerobius). C50 completely lost its activity when subjected to temperatures of 45°C or higher and when exposed to proteases. The extract remained stable over a wide range of pH values (6.0 11.0) and after incubation with solvents. Its antibacterial activity was almost completely lost following treatment with EDTA and recovered by the addition of zinc. The minimum inhibitory concentration of C50 was 6,25UA/mL, the same as the minimum bactericidal concentration. In 30 minutes all indicator cells were killed by the extract. The attempt to purify the antagonist substance performed by precipitation with ammonium sulfate (50% saturation) and ion exchange, exclusion, and reverse phase chromatography was not achieved.