Eradicational Action Of Diverse Antimicrobial Compounds On Fowl E.coli Biofilms

To approach the multidrug resistant mechanisms of fowl E.coli and provid theory basis of biofilm-mediated infection therapy,ESBLs of 27 E.coli isolates from chickens were detected with the standard double-disk synergy tests, antibacterial activities of 13 antimicrobial agents against the isolates were determined with the standard broth microdilution method. And the combined effect of clarithromycin and ciprofloxacin, clarithromycin and gatifloxacin, fosfomycin and ciprofloxacin, fosfomycin and gatifloxacin were determined with checkerboard method. The model of biofilms were established with the modified flat-board method in vitro, identified by the argentation,and ESBLs were detected with the standard double-disk synergy tests, and the ESBLs activities were determined with the double beam UV spectrophotometer,which was compared with the corresponding planktonic. Biofilms were cultivated with modified CBD device, antibacterial activities of antimicrobial agents against biofilms were determinined with the double dilution method, the combined effect of antimicrobial compounds used by the planktonic against biofilms were determinined and compared with the planktonic. The antimicrobial compounds were bolted by the effect of clarithromycin and fosfomycin on the formation of biofilms and synergistic action of the two antimicrobial agents to ciprofloxacin and gatifloxacin,combined with the MBIC of these combination. Eradicated the ripe biofilms with the antimicrobial compounds and surveyed it's effect.The results revealed that 15 strains of fowl E.coli produced ESBLs in 27 ,12 strains of fowl E coli didn't produce ESBLs, and the detection rate was 55.6 %; 19 strains of E. coli produced ESBLs and the detection rate was 70.4 %,4 non- ESBLs- producing strains produced ESBLs when becoming BBF.ESBLs activity of BBF(0.71±0.23U/mg) was 1.73 times of the corresponding planktonic(0.42±0.12 U/mg).The former was fairly higher than the latter.The detection results of antibacterial activities of 13 kinds antimicrobial agents against the planktonic showed that drug resistance of ESBLs-producing strains evidently elevated than non-ESBLs-producing strains. ESBLs-producing strains and non-ESBLs-producing strains were all resistant to the macrolides and the resistance rate reached 100%,except for azithromycin. The best antibacterial effect in quinolones was gatifloxacin, and it's resistance rate to ESBLs-producing strains was 8.3%,but non-ESBLs-producing strains were all susceptible to it. The checkerboard experience showed that clarithromycin and ciprofloxacin, clarithromycin and gatifloxacin presented independence or antagonistic action, fosfomycin and ciprofloxacin, fosfomycin and gatifloxacin presented addition or synergistic action; The detection results of antibacterial activities of 13 kinds antimicrobial agents against biofilm showed that whether the strain produced ESBLs or not,when it became BBF,it's drug resistance would increase 4 to 1024 times than the corresponding planktonic,and the tolerance of antimicrobial agents of ESBLs-producing strains is higher than non- ESBLs-producing strains. The checkerboard experience showed that clarithromycin and ciprofloxacin, clarithromycin and gatifloxacin presented addition or synergistic action, and preferred to additive action,fosfomycin and ciprofloxacin, fosfomycin and gatifloxacin presented addition or synergistic action.In the experiment of the effect of clarithromycin and fosfomycin to the formation of biofilm,using TSB containing clarithromycin and fosfomycin with 0 MIC,1/4 MIC,1/16 MIC cultivate biofilm,after 7 days argentated them and observed with micrography system:the structure of biofilm disposed of by antimicrobial agents was fairly different from the contrasting.The structure of disposed of biofilm was non-integrity, sporadic and irregular,which depended on the concentration of the antimicrobial agents;In the experiment of the synergistic action of clarithromycin and fosfomycin to ciprofloxacin and gatifloxacin, the MBEC of ciprofloxacin and gatifloxacin to biofilm disposed by clarithromycin and fosfomycin was predominantly degraded than the blank,which revealed that clarithromycin and fosfomycin had synergistic action to ciprofloxacin and gatifloxacin,but it independed on the concentration of the antimicrobial agents.Compared to the MBEC of different antimicrobial compounds, gatifloxacin and clarithromycin, gatifloxacin and fosfomycin had better effect than the others. In the experiment of bolting the antimicrobial compounds,detected the MBIC of gatifloxacin/clarithromycin (2:1,4:1,8:1,16:1),gatifloxacin/ fosfomycin (2:1,4:1,8:1,16:1)8 different compounds to 6 clinical strains, with the double dilution method, after statistical analysis with SPSS 11.5, determined the two antimicrobial compounds of gatifloxacin/clarithromycin(8:1) and gatifloxacin/fosfomycin(8:1).Selected 6 strains(3 ESBLs-producing strains and 3 non-ESBLs-producing strains) of fowl E. coli and established the in vitro model of biofilm,and used the two antimicrobial compounds of gatifloxacin/clarithromycin (8:1) and gatifloxacin/fosfomycin(8:1) to eradicate these biofilms and observed change of the structure at the different time.The result revealed that gatifloxacin/clarithromycin (8:1) eradicated these biofilms in 10~18d, gatifloxacin/fosfomycin(8:1) eradicated these biofilms in 7~15d.