Aggregatibacter actinomycetemcomitans colonization and persistence in a primate model.

Area of Science:

• Microbiology
• Oral Health
• Periodontics

Background:

• Aggregatibacter actinomycetemcomitans is a key pathogen in aggressive periodontitis, leading to tooth loss.
• Bacterial adherence and biofilm formation are critical for oral microbial survival and pathogenicity.
• Understanding microbial interactions is crucial for developing effective periodontitis treatments.

Purpose of the Study:

• To investigate the role of leukotoxin (ltx) variants of A. actinomycetemcomitans in colonization and biofilm formation.
• To assess the impact of Ltx production on bacterial attachment and survival in vivo.
• To identify microbial interactions that support A. actinomycetemcomitans colonization in the oral cavity.

Main Methods:

• Utilized a rhesus monkey model for in vivo colonization studies.
• Employed 16S rRNA sequencing and weighted network analysis to study microbial communities.
• Created and tested A. actinomycetemcomitans variants with varying leukotoxin (ltx) production levels in vitro and in vivo.

Main Results:

• Hyper-Ltx-producing strains of A. actinomycetemcomitans exhibited significantly higher prevalence and levels of colonization compared to wild-type or ltx mutants (P=0.05).
• In vitro assays confirmed that hyper-Ltx production enhances hydroxyapatite binding and biofilm formation.
• Colonizing A. actinomycetemcomitans strains were found to associate with lactate-producing bacteria, such as Leptotrichia, Abiotrophia, and Streptoccocci.

Conclusions:

• Hyper-production of leukotoxin (ltx) provides A. actinomycetemcomitans with a competitive advantage for tooth adherence and colonization.
• Increased attachment is linked to ltx gene expression and the upregulation of adherence-associated genes.
• The availability of lactate from associated species enhances the growth and survival of attached A. actinomycetemcomitans in the oral environment.