In those without chronic P. aeruginosa colonization and with a positive culture within six months of the initial sample, eradication treatment was conducted with inhaled tobramycin, and a second sample was obtained at the end of treatment, documenting a statistically significant reduction (p<0.045) in sCD40L levels, suggesting that the severity of infection by P. aeruginosa in CF is dynamically reflected by the concentration of sCD40L. This evidence concerns the gene CD40LG and infection.