Establishment of rat model of central venous catheter (CVC): associated infection and evaluation of the virulence of bacterial biofilms.

In this study, a central venous catheter (CVC)-associated infection model was established in rats to investigate and evaluate the effect of biofilms on the virulence of the pathogens. Twenty-four adult SD rats were randomly divided into biofilm positive (BF+) and biofilm negative (BF-) groups to be challenged with strains of S.epidermidis. Serum levels of inflammatory cytokines were measured and the infection rate and counts of bacteria cells were studied. Compared to rats of BF- group, the serum level of TNF and IL-6 significantly increased in rats of BF+ group (P < 0.01) and the level of IL-10 and IFN-γ significantly decreased (P < 0.01), striking the balance of pro-inflammatory/anti-inflammatory cytokines. The infection rate and bacterial counts in tissues and blood of rats of BF + group were significantly higher than those of rats of BF- group (P < 0.05).Inflammatory cell infiltration in vital organs (heart, lung, liver and kidneys) was more significant in rats of BF+ group than that of rats of BF- group. CVC-associated infection model can be successfully reproduced in rats by injecting 5 × 10(6) CFU of S.epidermidis. Biofilm formation can significantly enhance the virulence of the bacteria, leading to uncontrolled infection. The serum level of inflammatory cytokines, infection rate and the extent of inflammatory cell infiltration are important markers for evaluating the virulence of biofilm.