Analysis of selected virulence properties of Filifactor alocis

Abstract: ABSTRACT Filifactor alocis is a gram-positive rod-shaped bacterium, and several studies have demonstrated that the species is associated with periodontal disease. It has several proteins and properties that makes it a potential partner in crime in a disease process. Here we studied a small collection of 10 isolates of F. alocis, sampled for routine analysis at Oral Microbiology. One of the main questions of this exam project was to investigate if there was any genotypic and/or phenotypic differences between those isolates with potential association with virulence. To examine that we used a selection of laboratory methods, including PCR, SDS-PAGE, Silver-staining, extraction of membrane vesicles, Western immunoblotting and cytotoxicity assays on human macrophages. Our results show that there were both genotypic and phenotypic differences among the 10 strains. For example, they could be divided in two genotypes, based on carriage of gene (here denoted rtx) encoding a protein with similarity to Leukotoxin.  There were also differences in their protein content. Of the two tested F. alocis strains, frozen whole cell extracts from them both showed a similar dose-dependent cytotoxic effect on macrophages.  It also showed that the cytotoxicity did not depend on the rtx gene product since this study was conducted on two F. alocis strains, one with the rtx gene and the other without. In conclusion, our study could come in use in characterizing different F. alocis strains and their virulence factors in order to find future ways to reduce its virulence.