Chapter 47 - Tissue Cage Infection Model

Abstract

The animal model which best reproduces the clinical characteristics of human device-associated infection is the tissue cage infection model. In this model, perforated cylinders are implanted in the subcutaneous tissue. This model has been used in various animal species, however, guinea-pigs are the most commonly used species, especially for the study of pathogenesis, antimicrobial prophylaxis, and short-term therapy. For the study of long-term therapy, the rat model is preferred, as guinea-pigs do not support prolonged antimicrobial therapy. No specialized housing or care nor specific pretreatment is required, as long as animals are not infected. After implantation of the tissue cages, testing of antimicrobial agents should not be started before the cages are filled with clear interstitial fluid. It takes about three weeks until tissue-cage fluid is no longer hemorrhagic. After surgery or after infection, single housing is preferable as infected wounds are occasionally traumatized by cage-mates. In guinea pigs, two gas-sterilized tissue cages are inserted into each flank, and the skin is closed with metal clips. In rats only one cage is inserted into each flank. Tissue-cage infection can be induced either directly by injecting bacteria into the cages, or hematogenously by injecting them intracardiacly. Anesthetic (preferably intramuscular neuroleptanalgesia), opiate antidote, hair clippers or razor, skin disinfectant, a pair of curved scissors, surgical tweezers, scalpel handle plus blades, forceps for inserting and removing clips, three to five clips, four tissue cages, sterile towel with a hole, sterile surgical gloves, aerosol-based antiseptic plastic film, and three sterile gauze pads are required. The tissue cages used are Teflon tubes with an internal and external diameter of 8 mm and 10 mm respectively and 32 mm long.