Persistence of associated gram-negative bacteria in experimental actinomycotic lesions in mice

Area of Science:

• Microbiology
• Infectious Diseases
• Bacterial Pathogenesis

Background:

• Actinomycosis is a complex infection often caused by Actinomyces species.
• The role of polymicrobial interactions in actinomycosis pathogenesis is not fully understood.
• Gram-negative bacteria like Eikenella corrodens and Actinobacillus actinomycetemcomitans are frequently found in mixed infections.

Purpose of the Study:

• To investigate the role of specific gram-negative bacteria in the chronicity of actinomycotic infections.
• To establish a mouse model for studying mixed actinomycotic infections.
• To determine the persistence of E. corrodens and A. actinomycetemcomitans in the presence of Actinomyces israelii.

Main Methods:

• Establishment of mixed actinomycotic infections in a weanling mouse model.
• Inoculation with combinations of Actinomyces israelii and Eikenella corrodens.
• Inoculation with combinations of Actinomyces israelii and Actinobacillus actinomycetemcomitans.

Main Results:

• Acute lesions caused by E. corrodens or A. actinomycetemcomitans alone resolved within weeks.
• These gram-negative organisms persisted for up to 3 months in chronic lesions when coinfected with A. israelii.
• A. israelii facilitated the prolonged survival of coinfecting gram-negative bacteria.

Conclusions:

• Mixed infections with Actinomyces israelii and certain gram-negative bacteria can lead to persistent infections.
• The presence of A. israelii is crucial for the long-term survival of E. corrodens and A. actinomycetemcomitans in this model.
• Understanding these polymicrobial dynamics is important for managing complex actinomycotic infections.