Development and design of a novel in vivo chamber implant for the analysis of microbial virulence and assessment of antimicrobial therapy

An accurate reflection of the pathogenicity of microorganisms and the therapeutic effects of antimicrobial agents on their growth necessitates testing within an in vivo environment. We have developed a novel diffusion chamber, incorporating two 0.22 μm membrane filters, for the growth of in vivo organisms. The chamber, which is implanted intraperitoneally into the rat, has an external sampling portal. This portal allows multiple and sequential sampling of the microbial inoculum without killing the rat, thus significantly reducing the total number of animals used in such studies. In addition, the chamber is superior to other reported implants since it is well tolerated, reusable, easily constructed and can be used within two days of implantation. Staphylococcus epidermidis and a toxic shock syndrome toxin-1 (TSST-1) producing strain of S. aureus have been successfully grown within in vivo chambers, with 10⁸-10⁹ organisms per millilitre being recovered within 48 h. Scanning electron microscopy revealed clusters of staphylococci and fibrous material adhering to the inner surface of the filters, with numerous phagocytic cells attached to the outer side. Western immunoblotting indicated that higher levels of TSST-1 were produced by S. aureus grown in vivo as opposed to cells grown in vitro.