<i>Aggregatibacter actinomycetemcomitans</i> colonization and persistence in a primate model.

Abstract

<i>Aggregatibacter actinomycetemcomitans</i> is associated with aggressive periodontitis resulting in premature tooth loss in adolescents. Tooth adherence and biofilm persistence are prerequisites for survival in the oral domain. Here, using a rhesus monkey model, 16S rRNA sequencing, and weighted network analysis, we assessed colonization of <i>A. actinomycetemcomitans</i> variants and ascertained microbial interactions in biofilm communities. Variants in <i>A. actinomycetemcomitans</i> leukotoxin (<i>ltx</i>) were created, labeled, inoculated, and compared with their progenitor strain for in vivo colonization. Samples of tooth-related plaque were assessed for colonization at baseline and after debridement and inoculation of labeled strains. Null, minimal, and hyper-Ltx-producing strains were created and assessed for hydroxyapatite binding and biofilm formation in vitro. Ltx-hyperproducing strains colonized with greater prevalence and at higher levels than wild type or <i>ltx</i> mutants (<i>P</i> = 0.05). Indigenous and inoculated <i>A. actinomycetemcomitans</i> strains that attached were associated with lactate-producing species (i.e., Leptotrichia, Abiotrophia, and Streptoccocci). <i>A. actinomycetemcomitans</i> was found at 0.13% of the total flora at baseline and at 0.05% 4 wk after inoculation. In vivo data were supported by in vitro results. We conclude that hyper-Ltx production affords these strains with an attachment advantage providing a foothold for competition with members of the indigenous microbiota. Increased attachment can be linked to <i>ltx</i> gene expression and up-regulation of adherence-associated genes. Growth of attached <i>A. actinomycetemcomitans</i> in vivo was enhanced by lactate availability due to consorting species. These associations provide <i>A. actinomycetemcomitans</i> with the constituents required for its colonization and survival in the complex and competitive oral environment.