BACKGROUND:Bacterial biofilm is the main cause of the infection of the prosthesis.In vitro experiments confirmed that hypertonic sodium chloride and ethanol can apparently promote the formation of staphylococcal biofilms. There are no reports on the effects of ethanol and hypertonic environment surrounding the prosthesis on the formation of biofilms.
OBJECTIVE: To evaluate the effects of different environment factors surrounding the prosthesis on the growth of Staphylococcus epidermidis and bacterial biofilm formation after replacement.
METHODS: White rabbit models infected with Staphylococcus epidermidis on the prosthesis were established, and were randomly divided into hypertonic sodium chloride, ethanol and control groups (n=15). The bacteria were injected with 0.1 mL 4% sodium chloride and 4% ethanol into the knee of rabbits in the hypertonic sodium chloride and ethanol groups. The rabbits were injected with 0.1 mL 0.9% sodium chloride in the control group. Three rabbits were sacrificed at 2, 4, 6, 8 and 16 days after inoculated with bacteria. Synovial fluid, prosthesis and tissue surrounding infection were obtained. Bacterium was cultured to extract total RNA. The ica operon transcription levels were detected in the gene levels. Adhesion of bacteria on the surface of the prosthesis was observed using a scanning electron microscope. Tissues surrounding the prosthesis were observed using hematoxylin-eosin staining.
RESULTS AND CONCLUSION:Histological examination revealed that inflammatory cel infiltration was observed in al the rabbits at 4 days after injection. Colony formation was found at 16 days after injection. At 6 days after injection, inflammatory cel infiltration was observed in the ethanol and control groups. Scanning electron microscope showed that compared with the control group, the bacteria adhered to the prosthetic surface became more in the hypertonic sodium chloride and ethanol groups at 6, 8 and 16 days (P < 0.05). At 6, 8 and 16 days, the expression of icaA mRNA was significantly higher in the hypertonic sodium chloride and ethanol groups than in the control group (P < 0.05). These data showed that the environment factors could affect the growth of Staphylococcus epidermidis and bacterial biofilm formation.