FIG 5.

NO-np prevent MRSA strain 6498 biofilm formation in central venous catheters (CVCs) implanted in rats. MRSA biofilms were grown in vitro using catheter material as a substrate for 24 h at 37°C and then treated with 5 mg/ml of np or NO-np and compared to untreated controls. For biofilm formation, the initial inoculum was 10⁶ MRSA cells per plate. The microbial mass and viability of biofilm-associated cells were evaluated using the CFU (A) and FDA (B) assays. (A and B) Bars represent the average results from three catheters, and error bars denote SDs. Statistical significance (*, P < 0.05; ***, P < 0.001) was calculated by ANOVA. These experiments were performed twice, with similar results obtained each time. (C) Mean bacterial burdens in in vivo catheters incubated with 10⁶ MRSA cells/ml for 48 h are shown. CVCs implanted in the animals were treated with 5 mg/ml of np or NO-np at 24 h postinfection. This experiment was performed once using three animals (average results from three 5-mm pieces of each catheter per rat) per group. In addition, statistical significance (*, P < 0.05) was calculated using ANOVA. Bars represent the average results from three catheters, and error bars denote SDs. (D) Scanning electron microscopy (SEM) examination of MRSA strain biofilm formation on catheters placed in the jugular vein of a Sprague-Dawley rat and treated with PBS or 5 mg/ml of np or NO-np. Scale bar represents 1 μm for all images.