Objective To compare the difference of the Cif gene expression and the inflammation markers (such as WBC and CRP et al)between mucoid and non-mucoid Pseudonmonasaeruginosa,combining with the clinical data.Methods Real-time RT-PCR was used to determine the expression level of Cif in Pseudonmonas aeruginosa and clinical data were collected to discuss the relationship among the number of WBC,the level of CRP and the Cif gene expression.Results The expression level of Cif gene in mucoid Pseudonmonas aeruginosa had a significantly higher than the non-mucoid Pseudonmonas aerugi-nosa,which was statistically significant (t=2.09,P<0.05).Specimen data collected from patients with the infection of mu-coid or non-mucoid Pseudonmonas aeruginosa showed that the number of WBC and the level of CRP were not significantly different (t=0.65,0.60,P>0.05).The data also showed that the cystic fibrosis transmembrane conductance regulator in-hibitory factor (Cif)gene expression level had little correlation with the number of WBC (a=0.095,R2=0.029).Conclusion The expression of Cif gene may works for the biofilm formation of mucoid Pseudonmonas aeruginosa,which maybe a new virulence factor to Pseudonmonas aeruginosa.