Tight-adherence genes of Actinobacillus actinomycetemcomitans are required for virulence in a rat model

Abstract

Actinobacillus actinomycetemcomitans is a Gram-negative coccobacillus that has been associated with localized aggressive periodontitis and infections of the heart, brain, and urinary tract. Wild-type clinical isolates have the remarkable ability to adhere tenaciously and nonspecifically to solid surfaces such as glass, plastic, and hydroxyapatite. Adherence by A. actinomycetemcomitans is mediated by the tight-adherence (tad) gene locus, which consists of 14 genes (flp-1-flp-2-tadV-rcpCAB-tadZABCDEFG). All but 2 of the genes have been shown to be required for the secretion and assembly of long, bundled Flp1 fibrils. To test whether the tad locus is required for colonization and disease, we developed a rat model for periodontal disease. To mimic the natural route of infection, Sprague-Dawley rats were inoculated orally by adding bacteria directly to their food for 8 days. After inoculation with wild-type or mutant strains defective in adherence (flp-1 and tadA), the rats were assessed for colonization of the oral cavity and pathogenesis. Wild-type A. actinomycetemcomitans was able to colonize and persist for at least 12 weeks in the oral cavity, elicit a humoral immune response, and cause significant bone loss in rats. In contrast, rats fed flp-1 or tadA mutant strains showed no bone loss and their immune responses were indistinguishable from those of the uninoculated controls. These results demonstrate the critical importance of the tad locus in the colonization and pathogenesis of A. actinomycetemcomitans. nonspecific adherence ͉ tad genes ͉ pathogenesis ͉ localized juvenile periodontitis

Ocorrência de genes tad associados à formação de biofilme em isolados de Pasteurella multocida de pulmões de suínos com pneumonia

“…Com seu lócus gênico composto por flp1, flp2, tadV, rcpC, rcpA, rcpB, tadZ, tadA, tadB, tadC, tadD, tadE, tadF e tadG ou apenas flp-rcp-tad, têm sido implicado na patogênese de diversos gêneros bacterianos (Tomich et al 2007). Schreiner et al (2003) O objetivo deste trabalho foi analisar a ocorrência de P. multocida em pneumonias de suínos e da microbiota de pulmões sem lesão e a ocorrência dos genes do lócus tad nestes isolados.…”

Ralstonia solanacearum Needs Flp Pili for Virulence on Potato

“…actinomycetemcomitans (Schreiner et al 2003), Haemophilus ducreyi (Nika et al 2002;Spinola et al 2003), Yersinia ruckeri (Fernandez et al 2004) and Pasteurella multocida (Fuller et al 2000). In contrast to these human and animal pathogenic bacteria, the functional significance of the tad locus in phytopathogenic bacteria has not yet been reported.…”

Fimbriae-associated Genes are Biofilm-forming Factors in Aggregatibacter actinomycetemcomitans Strains

“…The gene associated with adherence by A. actinomycetemcomitans is mediated by the tight-adherence (tad) gene locus, which consists of 14 genes (flp-1-flp-2-tadV-rcpCABtadZABCDEFG) 20) . The genes for rcpA and rcpB, are tandemly located downstream of the fimbriae genes fa and flp 11,12) .…”