Mouse Model of Catheter-Associated Biofilm

The impact of TLR2 or TLR9 on biofilm formation and growth in vivo was assessed using a mouse model of catheter-associated biofilm infection as previously described with minor modifications (50 (link), 51 (link)). Briefly, WT, TLR2 KO, or TLR9 KO mice received subcutaneous implants of sterile 1 cm catheter segments in both flanks under general anesthesia. One catheter was inoculated with 20 μl (5 × 10⁵ CFU) log-phase USA300 LAC::lux, whereas the other catheter received an equal volume of PBS to evaluate the foreign body response. The extent of biofilm formation was monitored longitudinally in the same cohort of mice using an In Vivo Imaging System (IVIS Spectrum; Caliper Life Sciences) under isoflurane anesthesia and separate groups of animals were sacrificed at days 3, 7, and 10 post-infection to determine absolute bacterial burdens associated with catheters and surrounding tissues. In experiments designed to assess the ability of identical S. aureus inoculums to establish biofilm versus subcutaneous infection in the absence of an indwelling device, mice received subcutaneous injections of USA300 LAC::lux (5 × 10⁵ cfu in 20 μl) and processed as described above for biofilm infections.