A porcine bimicrobial abscess model for testing interventional treatments

Abstract Background Abscess formation is a host defense mechanism to contain the spread of infection. Abscesses can affect any part of the body and are common sequelae to complications of trauma, surgery, systemic infections and other disease states. Most models for abscesses are in small animals. Pursuant to the goal of developing more advanced treatments for abscesses, we sought to develop a large animal model which would reasonably mimic a fluid-filled human abscess. Methods Domestic swine were inoculated with a bimicrobial mixture of Bacteroides fragilis ( B. fragilis ) and Escherichia coli ( E. coli ) supplemented with an irritant (dextran). Inoculations were performed under ultrasound guidance in the muscle, subcutaneously or intradermally within the same animal. Fourteen days after inoculation, lesions were imaged with ultrasound, resected and prepared for histological evaluation. Results Injection of bimicrobial (aerobic and anaerobic) bacterial mixtures at multiple sites in a pig produced multiple lesions with histological features similar to encapsulated and multiloculated/multichamber abscesses often observed clinically in humans. Important salient features include the formation of a connective tissue capsule surrounding histologically nearly amorphous pus. Conclusions This paper provides the first description of a pig model for multiloculated abscesses. This animal model could potentially enable the evaluation of new technologies to replace or augment the current standard of care (image-guided percutaneous abscess drainage with antibiotics).