| Objective:Select 3 kinds of antimicrobial peptides through the minimum inhibitory concentration and erythrocyte hemolysis experiment,establish an animal model of bacterial endophthalmitis in rabbits,antimicrobial peptides and antibiotics were injected into the vitreous separately,observe the treatment of bacterial endophthalmitis.Method:(1)Minimal inhibitory concentration:Detection of the minimum inhibitory concentration of five antimicrobial peptides against methicillin-resistant Staphylococcus aureus by the micro broth dilution method.(2)Erythrocyte hemolysis experiment:Prepare 4%red blood cell suspension,incubate with different concentrations of antimicrobial peptides at 37℃for 1h,measure the absorbance to calculate the hemolysis fraction of antimicrobial peptides.(3)36 New Zealand white rabbits were injected into the vitreous with a concentration of 1×10~3CFU/ml methicillin-resistant Staphylococcus aureus to establish a bacterial endophthalmitis model.24 hours after injection of bacteria,intravitreal injection of drugs for treatment,observation and scoring.According to the treatment drugs,36 white rabbits were divided into 6 groups.Group A:PBS solution with volume of 0.1ml was injected into vitreous;Group B:Vancomycin solution with concentration of 1mg/0.1ml was injected into vitreous.Group C:Ampicillin solution with concentration of 1mg/0.1ml was injected into vitreous.Group D:Antibacterial peptide IK-12 solution with concentration of 1mg/0.1ml was injected into vitreous.Group E:Antibacterial peptide IP-12 solution with concentration of 1mg/0.1ml was injected into vitreous.Group F:Antibacterial peptide WP-12 solution with concentration of 1mg/0.1ml was injected into vitreous.Observe and score the cornea,conjunctiva,vitreous and retina at 0h,24h,48h,72h after the injection of drugs.72 hours after the injection of the drug,the rabbits were anesthetized by overdose.Eyes were harvested under sterile conditions,5eyeballs in each group for plate count and 1 eyeball for Histopathologic Examination.Results:(1)Minimal inhibitory concentration:When the concentration of the bacterial solution is 1×10~8CFU/ml,the minimum inhibitory concentration of antimicrobial peptides is 8-64μg/ml.When the concentration of the bacterial solution is 1×10~5CFU/ml,the minimum inhibitory concentration of antimicrobial peptide is 4-16μg/ml.(2)Erythrocyte hemolysis experiment:Among the five antimicrobial peptides,IK-12 and PP-12 have higher hemolysis fractions.When the concentration reaches 1000μg/ml,the hemolysis fraction exceeds 30%,while PK-12 and WP-12 have lower hemolysis fractions.At 1000μg/ml,the hemolysis fraction is less than 10%.When the concentration drops to 250μg/ml,the hemolysis fraction of all antimicrobial peptides does not exceed 4%.(3)When the drug was injected into the vitreous,there was no significant difference in the clinical scores of endophthalmitis in all groups(p>0.05).Intravitreal injection of drugs for 24h,48h and 72h,there were significant differences in the clinical scores of endophthalmitis in all groups(p<0.05).Histopathologic Examination:Group A has no complete retinal layer,and the vitreous body is full of inflammatory cells.Group B:Part of the retinal necrosis,the vitreous body is full of inflammatory cells.Group C:The structure of the retina is roughly normal,and no inflammatory cells are seen in the vitreous body.Group D:The structure of the retina is roughly normal,with scattered inflammatory cells in the vitreous body.Group E:The structure of the retina is roughly normal,with scattered inflammatory cells in the vitreous body.Group F:The structure of the retina is roughly normal,with scattered inflammatory cells in the vitreous body.Conclusion:Antimicrobial peptides IK-12,IP-12 and WP-12 have low minimal inhibitory concentration against methicillin-resistant Staphylococcus aureus and low toxicity to red blood cells.Early intravitreal injection of antimicrobial peptides IK-12,IP-12 and WP-12 can effectively treat bacterial endophthalmitis in rabbits. |
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