Study On The Role Of Snake Venom Cathelicidin Antimicrobial Peptides Against Infection When Used To Pretreat Artificial Implants

Objective:To investigate whether snake venom cathelicidin antimicrobial peptides will degradate and lose anti-bacterial activity in the presence of plasma, and whether artificial implants pretreated by snake venom cathelicidin antimicrobial peptides have anti-bacterial effects in experimental animals.Methods:1 Test the antibacterial activity of snake venom cathelicidin antimicrobial peptides in presence of plasma:Add snake venom cathelicidin antimicrobial peptides in LB with and without plasma to get different concentration of antimicrobial peptides including 32μg/ml,16μg/ml,8μg/ml,4μg/ml,2μg/ml, lμg/ml, 0μg/ml, and add 10μl (5×106cfu/ml) of E.coli ATCC25922 in each EP which were then cultured at 37℃for 16 hours. Determinate the OD values of A and B groups.2 In vitro test, Test the anti-bacterial activity of catheters and dacron patches pretreated with four different methods against E.coli ATCC25922 on the first day and the 7th day and against resistant strains E. coli on the 7th day with agar diffusion method.3 Establish rabbit urine indwelling catheters infection model and subcutaneous dacron patches infection model:Collect blood to determinate cytokines concentration and urine to incubate on the 1st day,5th day,10th day. On the 10th day, the catheters were removed for bacterial culture and were observed with scanning electron microscopy. The rabbit bladders were examinated by pathology. Dacron patches were removed for bacterial culture and were observed with scanning electron microscopy on the 7th day, and the subcutaneous tissues were used for pathological examination and cytokines determination.Results:1 snake venom cathelicidin antimicrobial peptides had a strong anti-bacterial effect both in and without the presence of plasma on E.coli ATCC25922, and the MIC were at the range of 4-8μg/ml. The statistical analysis showed no significant difference (P> 0.05) between them.2 Both the catheters and dacron patches with cefoperazone+chitosan and that with the peptide＋chitosan had a strong anti-bacterial activity on E.coli ATCC25922, and the inhibitory effect on E.coli ATCC25922 were still significant even when they were immersed in plasma for 7 days, but that with cefoperazone+chitosan group lost their anti-bacterial activity on drug-resistant strains of E.coli, while that with the peptide+chitosan group still had a continued and significant anti-bacterial activity. The anti-bacterial activity unit value was 26.67±5.77.3. The cefoperazone+chitosan group and the peptide+chitosan group significantly inhibited the formation of biofilm in the rabbits, which greatly decreased the number of planktonic bacteria in biofilm surface and made the infection of experimental animals less possible.Conclusion:The snake venom cathelicidin antimicrobial peptides would not degradate and lose anti-bacterial activity in the presence of plasma, the snake venom cathelicidin antimicrobial peptide had a significantly anti-bacterial effect on standard strains of E. coli and the resistant strains; The application of artificial implants pretreated with snake venom cathelicidin antimicrobial peptides which could significantly inhibit biofilm formation could regulate immune status and protect the experimental animals.