Effects Of Minocycline On Staphylcoccus Epidermidis Biofilm Associated With Peritoneal Dialysis Cathete In Vitro

Objective:Establish the BF model of staphylococcus epidermidis associated with peritoneal dialysis cathete in vitro, to investigate the effect of minocycline on the biofilm formation and destruction on biofilms structure.Methods:(1) Biofilm formation in vitro:The clinical isolate Staphylococcus epidermidis was used for biofilm formation in vitro. SE were cultivated in LB medium-peritoneal dialysis catheter system to establish bacterial biofilm model. BF was observed by scanning electron microscope(SEM).(2) Effect of minocycline on adherence of S. epidermidis to peritoneal dialysis catheter:Minimum inhibitory concentration (MIC) of minocycline was measured by broth microdilution method. The control group and minocycline group were set up, and then add minocycline at the beginning of construction of biofilm models. On the1st and3rd day, observe the structure of biofilm by SEM, detect viable bacteria counts in the biofilm by serial dilution method, semi-quantity biofilm by crystal violet staining.(3)Effect of minocycline on S. epidermidis in biofilm:different concentrations of minocycline was applied to the early and mature biofilms for0、4、8、24hours respectively. BF was observed by scanning electron microscope(SEM), the numbers of viable bacteria were measured by serial dilution.Results:(1) After cultivated for1day, young and thin BF can be seen on the surface of carriers under SEM. After cultivated for3days, thick and mature BF can be seen under SEM.(2) The MIC of minocycline to S. epidermidis is4μ g/ml. At concentrations of1/16MICs, bacterial adhesion was inhibited by minocycline. The viable bacteria counts in the biofilm of minocycline group is less than control group (P<0.05) and the biofilm by crystal violet staining in minocycline group is less than the control group after incubated for1d or3d (P<0.05). Compared with the control group, myxoid substance was less than the control group and baterials were scattered.(3) At concentration of1/4MIC, the early biofilms could be disrupted by minocycline while for mature biofilms, the disruption concentration was1/2MIC. Whether for early biofilms or mature biofilms, the viable bacteria counts in the biofilm was less than control group (P<0.05) after treated by minocycline. Compared with the control group, the scale of the biofilm in the minocycline group are smaller than the control group are smaller than the control group myxoid substance was less than the control group and baterials were scattered, three-dimensional configuration disappeared.Conclusions:(1) The clinical isolate Staphylococcus epidermidis could form biofilms on the surface of peritoneal dialysis catheter;(2) Minocycline can restrain S. epidermidis from forming biofilm on the surface of peritoneal dialysis catheter at the subinhibitory concentration of1/16MIC;(3) Minocycline was destructive of both early and mature biofilms.