Abstract:

Abstract:Objective
To investigate the effects of mesna or/ and in combination with ciprofloxacin on biofilm of Pseudomonas aeruginosa.Methods The broth microdilution method was performed to determine the minimal inhibitory concentration(MIC) of mesna and ciprofloxacin to PAO1,then a biofilm model of Pseudomonas aeruginosa in vitro was established,the biofilms were randomly divided into 3 groups: control group,low-dose mesna group and high-dose mesna group,the parameters　of biofilm structure were analyzed through pictures from CLSM with Image Structure Analyzer(ISA)software after the biofilms were treated with mesna;then the biofilms of Pseudomonas aeruginosa were randomly divided into: mesna group,CIP group,mesna+CIP group,they were treated with mesna,ciprofloxacin (alone and in combination),three dimensional images of the biofilms were obtained with Amira 5.2 software. Through a aboard design,different consistence  mesna (0,0.5,1.0，2.0 and 4.0 g•L^-1)were respectively combined with different consistence ciprofloxacin （0，1/2，1，2，4，8 MIC）,the number of bacteria in biofilms was measured by agar plate.Results The MIC values against PAO1 were 10 g•L^-1 for mesna and 0.12 mg•L^-1 for ciprofloxacin.The results of ISA showed that with the treatment of low-dose mesna,the biofilms  were decreased in thickness,average difusion distance(ADD)and textual entropy(TE) as compared with control group (P<0.01),however the areal porosity(AP) was increased(P<0.01),the same tendency of these parameters was observed in the high-dose group and the effects were more obvious(P<0.01); The images from CLSM showed that the  biofilms in mesna (2 g•L^-1) group were intensive and thicker,the masses of alive bacteria were found in the biofilms but no dead bacteria;ciprofloxacin(2 MIC) decreased the alive bacteria,the dead bacteria were increased relatively slightly;the biofilms were thinner and more scattered,plenty of bacteria were killed in the presence of ciprofloxacin (2 MIC) and mesna (2 g•L^-1).The single use of mesna at the concentration of 2 g•L^-1 could significantly decline the viable cells in biofilms,the individual use of ciprofloxacin at 2 MIC could significantly desease the total bacterial quantity;however,when 1 g•L^-1 mesna was combined with 1 MIC ciprofloxacin,the viable counts in biofilms were less than they were given alone.Conclusion Mesna can destroy the construction of biofilm of Pseudomonas aeruginosa and has the synergistic effect on bactericidal activity with ciprofloxacin.

Key words: Pseudomonas aeruginosa；biofilm；mesna；ciprofloxacin