Biomaterial-associated persistence of Streptococcus epidermidis in pericatheter macrophages

Biomaterial surfaces may be modified to reduce bacterial adhesion. The susc eptibility in mice to Staphylococcus epidermidis infection in tissue surrou nding the commonly used catheter materials-silicon elastomer (SE), polyamid e (PA), and their surface-modified polyvinylpyrrolidone (PVP)-grafted deriv atives, SE-PVP and PA-PVP, respectively-was assessed. Abscesses developed a round SE-PVP Around SE, PA, and PA-PVP catheters, no signs of infection wer e observed, although mice carrying PA-PVP developed septicemia after 14-21 days. S. epidermidis was cultured from the tissue surrounding PA-PVP segmen ts. Cells around PA-PVP segments containing large numbers of bacteria were identified as macrophages by use of immunohistochemistry and electron micro scopy. This persistence of intracellular bacteria was also observed around SE-PVP, SE, and PA, catheters, although to a lesser extent. The cytokine pr ofiles around the 4 materials were different. Implanted biomaterial induces an inflammatory response favorable to the persistence of S. epidermidis. I ntracellular persistence of bacteria inside macrophages may be a pivotal pr ocess in the pathogenesis of biomaterial-associated infection.