Leukotoxic Activity of Actinobacillus Actinomycetemcomitans Isolated From Human and Non-Human Primates

Abstract

Actinobacillus actinomycetemcomitans is a clinically relevant periodontopathogenic Gram-negative coccobacillus that produces a leukotoxin of the RTX cytolysin family. In this study, we evaluated the leukotoxic activity of A. actinomycetemcomitans strains isolated from human and marmosets by Trypan blue exclusion and by the chemiluminescence assays. Among eight A. actinomycetemcomitans human strains studied, two (P 2.17 and P 8.12 ) were classified as high leukotoxin producers and among eight marmoset strains, one (M 22.11 ) showed high leukotoxin production, as determined by Trypan blue exclusion assay. The reference strains ATCC 29523 and FDC Y4 respectively behaved like moderate and low producers. The chemiluminescence assay was used to evaluate the leukotoxic activity of M 22.11 and P 2.17 strains submitted to different growth conditions. Leukotoxic activity was detected on cells at the logarithmic phase and was similar under anaerobic and microaerophilic growth conditions. It was greatly reduced when cells were grown at glucose concentrations lower or higher than 0.75% (0.25% and 1.5%) in thioglycolate medium. Leukotoxin production mainly by the M 22.11 strain was low in BHI broth, whereas production in TSB medium showed a similar level as in thioglycolate broth medium. Sodium bicarbonate at 10 mM did not affect leukotoxin production.

Oleoresins and naturally occurring compounds of Copaifera genus as antibacterial and antivirulence agents against periodontal pathogens

“…This test was carried out by following the methodology described by de Lima et al 41 . Mononuclear human leukocytes (LMNS) were isolated from an enriched fraction of venous blood leukocytes by using Histopaque 1077 (Sigma-Aldrich); the manufacturer's instructions were followed.…”

Immunoglobulin G proteolytic activity of Actinobacillus actinomycetemcomitans

“…Moreover, A. actinomycetemcomitans produces a bacteriocin that plays an important ecological role in regulating the intra-and inter-specific oral microbiota (6,10,11). Antibodies produced against these virulence factors may be beneficial to the host, but A. actinomycetemcomitans produces proteases that cleave immunoglobulins [Igs] (5) and factors that can inhibit Igs production by human B cells (15) and the lymphoproliferative response (17).…”