Abstract: Objective To investigate the role of chlorogenic acid, c-di-GMP and human bactericidal peptide LL-37 in biofilm formation(BF) of Pseudomonas aeruginosa(PA) and drug resistance. 
Methods Wild-type pseudomonas aeruginosa strain(PAO1) was selected to carry out the study, and the minimum inhibitory concentration(MIC) of chlorogenic acid, c-di-GMP and human germicide LL-37 on PA was determined by broth dilution method. Crystal violet quantitative method was used to detect the scavenging effects of chlorogenic acid, c-di-GMP and human germicidal peptide LL-37 in PA-BF formation, and PA motion test was used to detect the effects of chlorogenic acid, c-di-GMP and human germicidal peptide LL-37 on PA motion ability. The effects of chlorogenic acid, c-di-GMP and human bactericidal peptide LL-37 on the structure and survival of PA-BF were observed under fluorescence microscope. 
Results The value of MIC of human germicidal peptide LL-37, chlorogenic acid and c-di-GMP was 64 mg/L, 256 mg/L, and 32 mg/L, respectively. Compared with the c-divGMP group, the value of OD590nm human germicidal peptide LL-37 group, chlorogenic acid group and blank group significantly decreased, which was significantly lower in human bactericidal peptide LL-37 group and chlorogenic acid group(P＜0.05). Compared with the negative control group, the PA diameter in exercise testing of the human germicidal peptide LL-37 group, the chlorogenic acid group and the c-di-GMP group significantly decreased, which was significantly lower in human germicidal peptide LL-37 group and the chlorogenic acid group, as compared with the c-di-GMP group(P＜0.05).The survival of PA in blank group and c-divGMP group was better than that in human germicidal peptide LL-37 group and chlorogenic acid group. The fluorescence in blank group and c-di-GMP group was mainly green, while the fluorescence in human germicidal peptide LLv37 group and chlorogenic acid group was mainly red and orange.Compared with c-di-GMP group, the drug resistance rate of human germicidal peptide LL-37 group, negative control group and chlorogenic acid group significantly decreased, and compared with the negative control group, the drug resistance rate of human germicidal peptide LL-37 group and chlorogenic acid group significantly decreased(P＜0.05). 
Conclusion Both chlorogenic acid and human bactericidal peptide LL-37 can clear PA-BF to a certain extent, and c-di-GMP can regulate the BF formation of PA by inhibiting cell motor ability. Chlorogenic acid, human bactericidal peptide LL-37 and c-di-GMP can be used as a new direction for subsequent prevention and control of PA-BF.

Key words: pseudomonas aeruginosa, biofilm, drug resistance