INVESTIGATION OF MICROBIAL-GROWTH INVIVO - EVALUATION OF A NOVEL INVIVO CHAMBER IMPLANT SYSTEM

An intraperitoneal chamber implant system has been used to investigate the phenotype of Staphylococcus aureus growing in the rat and the effect of the antibiotic flucloxacillin on bacterial growth in vivo. Titanium chambers were implanted in the peritoneum: a period of 3-4 days equilibration allowed diffusion of host proteins into the chamber fluid prior to inoculation with bacteria. S. aureus inoculated into the chamber fluid, grew rapidly over a 72 h period, reaching counts of > 109 per ml. Organisms harvested from chambers were analysed by SDS-PAGE and showed significant differences in polypeptide profiles from the same strain grown in nutrient broth in vitro. Analysis of whole cell extracts by Western-blotting revealed that protein A expression was repressed in S. aureus grown in vivo. Following subcutaneous administration, flucloxacillin levels in serum peaked earlier and were higher than those detected in chamber fluid. The inhibitory effect of the antibiotic on the growth of S. aureus in chambers in treated animals could be monitored easily by sequential sampling of the chamber fluid. These results indicate the potential of the chamber implant model for investigation of microbial phenotype in vivo and development of alternative methods for assessment of antimicrobial efficacy in vivo.