The effects of Acacia arabica gum on the in vitro growth and protease activities of periodontopathic bacteria.

The antibacterial activity of acacia gum was assessed using fresh isolates and reference strains of Actinobacillus actinomycetemcomitans, Capnocytophaga spp., Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. A fine aqueous suspension of gum was produced by sonication and then a soluble fraction isolated by centrifugation and membrane filtration. These preparations were incorporated into columbia agar at doubling concentrations. Growth of P. gingivalis and P. intermedia cultures on the agar was inhibited by whole gum sonicate at concentrations of 0.5-1.0% w/v. Both species showed reduced susceptibility when horse blood was present in the agar. The gum soluble fraction did not inhibit growth of any bacterial culture. The effect of acacia on bacterial proteases was examined with cell sonicates from log phase broth cultures. Enzyme activities were determined by fluorimetric assay with various synthetic peptide substrates. Most protease activities reduced in the presence of 0.5% w/v gum sonicate, with the trypsin-like activities of P. gingivalis and P. intermedia proving most sensitive. The gum soluble fraction was nearly always less inhibitory than the sonicate. The action of acacia gum against suspected periodontal pathogens and their enzymes suggests that it may be of clinical value.