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Effect of co-aggregation on the pathogenicity of oral bacteria
K Ochiai1, T Kurita-Ochiai, Y Kamino
1Department of Microbiology, Nihon University, School of Dentistry at Matsudo, Chiba, Japan.
Abstract:
The pathogenicity of oral bacteria was studied by measuring the development of subcutaneous abscesses in mice after infection with Actinomyces viscosus and Streptococcus mitis either singly or as co-aggregated pairs. Heat-treated cells were also tested. The pathogenicity of the co-aggregates was examined in various viable and heat-treated combinations of the two bacterial species. More abscesses were formed by A. viscosus than S. mitis at all the bacterial concentrations tested. Also, abscess formation by co-aggregates of the two strains produced a higher percentage of abscess formation than those caused by infection with pure suspensions of A. viscosus or S. mitis. Co-aggregated cells were more resistant to phagocytosis and killing by neutrophils in vitro and in vivo. Furthermore, A. viscosus in co-aggregates were resistant to killing after engulfment by neutrophils. These results suggest that oral bacteria that are able to co-aggregate may resist phagocytosis, and this ability may be linked with pathogenicity.
Insights
Co-aggregation of oral bacteria like Actinomyces viscosus and Streptococcus mitis enhances abscess formation and resistance to immune cells. This bacterial co-aggregation may be a key factor in oral pathogenicity.
Area of Science:
- Oral microbiology
- Bacterial pathogenicity
- Immunology
Background:
- Oral bacteria, including Actinomyces viscosus and Streptococcus mitis, can cause infections.
- Understanding the factors contributing to bacterial pathogenicity is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the pathogenicity of Actinomyces viscosus and Streptococcus mitis, both individually and as co-aggregated pairs.
- To determine if co-aggregation influences bacterial resistance to host immune defenses.
Main Methods:
- Subcutaneous abscess development was measured in mice after infection with single strains or co-aggregates of A. viscosus and S. mitis.
- Heat-treated bacterial cells were also used to assess viability effects.
- Resistance to phagocytosis and neutrophil killing was evaluated in vitro and in vivo.
Main Results:
- Actinomyces viscosus was more abscess-forming than Streptococcus mitis across tested concentrations.
- Co-aggregates of A. viscosus and S. mitis induced higher abscess formation rates than pure cultures.
- Co-aggregated bacteria exhibited increased resistance to phagocytosis and neutrophil-mediated killing.
Conclusions:
- Bacterial co-aggregation enhances pathogenicity by increasing resistance to immune clearance mechanisms.
- The ability of oral bacteria to co-aggregate is a significant factor linked to their pathogenic potential.