The Effect Of The Combination Of Fosfomycin And Aminoglycosides On The Formation Of Pseudomonas Aeruginosa And On Renal Toxicity Induced By Aminoglycosides In Rat

Objective:To study the combination effect of fosfomycin and aminogtycosides on the formation of biofilm of Pseudomonas aeruginosa(PA)in vitro and in vivo,and evaluate the protective effect of fosfomycin on renal toxicity induced by aminoglycosides in rat.Methods:Using toothful broth dilution method and the method of checkboard plot to survey the minimum inhibition concentration from different concentration combination of 5 groups antibacterials(fosfomycin and 5 kinds of aminoglycosides)on 20 clinical isolated PA strains,and FIC index were used to assessment combined effect.The modified plate culture method was used to establish biofilm model in vitro with which the morphology of PAO1 biofilms were observed by SEM,ARG after treated with different dosages of fosfomycin and aminoglycosides.PAO1 biofilms were analyzed by computer image analysis system.The viable counts of bacteria in PAO1 biofilms were detected after treated with fosfomycin and aminoglycosides by MTT method.Evaluate the effect of the combination of fosfomycin and aminoglycosides on.PAO1 biofilm and on renal toxicity induced by aminoglycosides in rat through determining body weight,body temperature,C-reactive protein,white cell count,colony count of infected part-tissued and tissue cage,serum creatinine,blood urea nitrogen,urinary production,urine n-acetyl-β-d-glucosaminidase,nephridial tissue pathology light microscope observation,nephridial tissue pathology transmission observation.Results:The MIC₅₀of the antibiotics were descended obviously.The FIC indexes less than 0.5,0.5 to 1,1 to 2,and more than 2 were 65%～85%,10%～20%, 5%～15%,0%respectively.ARG of PAO1 biofilms show that cluster bacilli surrounded by dense black stained substance.The restraining effect on the formation of biofilm of combination groups were more than that of non-combination groups.Dense black stained substance of combination groups were fewer than non-combination groups'.The SEM showed that bacteria were both bacillus surrounded by accidented material and the bacteria were connected each other with mucoid substance.The restraining effect on the formation of biofilm of combination groups were more than that of non-combination groups. The computer image analysis system showed that the average optical value of combination groups were significantly lower than non-combination groups(P＜0.05).MTT method showed that the viable counts of bacteria of combination gruops were significantly lower than non-combination groups' with the increasing dosages of fosfomycin and aminoglycosides(P＜0.05).Tissue cage experiment in rat showed that the body temperature,C-reactive protein,white cell count,decrement of decreased body weight of combination groups were decreased significantly than non-combination groups and control groups(P＜0.05).The colony count of infected part-tissued and tissue cage of combination groups were decreased significantly than other groups.The colony count of infected part-tissued were fewer than that of tissue cage but difference not statistically significant.The SEM of tissue cage showed that the clearance of combination groups were more significantly than that of non-combination groups.The level of serum creatinine,blood urea nitrogen,urine n-acetyl-β-d-glucosaminidase of the combination groups were raised up than control groups after administration for 4 weeks but difference not statistically significant(P＞0.05),and that of the non-combination groups were raised up significantly than other groups(P＜0.05).The nephridial tissue pathology light microscope observation and nephridial tissue pathology transmission observation showed the level of renal damage induced by the groups Of fosfomycin+Isepamicin were lower than that of the grouos of Isepamicin(P＜0.05). Conclusions:There were obvious differences between combination fosfomycin and aminoglycosides groups and non-combination groups in the formation of PA biofilm.Synergistic action of fosfomycin to aminoglycosides is verified. Meanwhile,the animal experiment showed that fosfomycin may relieve renal damage induced by aminoglycosides.