Infectivity of organisms recovered from polymicrobial abscesses

Area of Science:

• Microbiology
• Infectious Diseases
• Bacteriology

Background:

• Clinical abscesses harbor diverse bacterial communities, including anaerobes and aerobes.
• Identifying the primary pathogens responsible for abscess formation is crucial for understanding infectious processes.

Purpose of the Study:

• To determine the role of bacterial capsules in the pathogenesis of abscesses.
• To identify key bacterial pathogens contributing to clinical abscesses using a murine model.

Main Methods:

• Bacteria isolated from 13 human clinical abscesses were inoculated subcutaneously into mice.
• The ability of encapsulated and non-encapsulated isolates to induce abscesses independently and in combination was assessed.
• Bacterial recovery from induced abscesses was performed to confirm pathogen survival and contribution.

Main Results:

• Sixteen encapsulated bacterial isolates, including various Bacteroides species, anaerobic gram-positive cocci, Clostridium species, and Escherichia coli, were identified.
• All but one encapsulated organism could induce abscesses independently and were recovered when co-inoculated.
• Non-encapsulated organisms generally failed to induce abscesses alone but could survive and contribute to abscess formation when paired with encapsulated bacteria.

Conclusions:

• Possession of a bacterial capsule significantly increases the likelihood of an isolate being a major contributor to abscess formation.
• Bacterial capsules are critical virulence factors in the pathogenesis of subcutaneous abscesses.
• The murine subcutaneous abscess model is effective for evaluating bacterial pathogenicity and the role of capsules.