Therapeutic Effects Of Antimicrobial PePtides On Mastitis Caused By Staphylococcus Aureus In Mouse Model

In order to study the therapeutic effect of maggot AMPs on mouse mastitis and lay the theoretical foundation for the clinical application of AMPs in the treatment of mastitis in dairy cows.The fly larvae AMPs was isolated and purified,its antibacterial activity was detected,and it was used to treat the pathological model of mastitis in mice.The clinical symptoms of mice during the treatment were observed,and the mammary gland pathological tissue of the mice after necropsy was examined,the results of the study are as follows:1 The Coomassie brilliant blue method was used to determine the concentrations of AMPs of fly larvae.The experimental results showed that:fly larvae induced by S.aureus can significantly increase the expression levels of AMPs in fly maggots,resulting in the production of maggots induced by S.aureus;AMPs concentrations were significantly higher than uninduced fly lice?p<0.05?.The susceptibility test method was used to determine the antibacterial activity of the fly larvae antibacterial peptides.The results showed that the inhibition zone diameter of antibacterial peptides of fly larvae?19.97±0.65mm?was significantly greater than that of uninfected fly larvae?13.82±0.79 mm??p<0.05?.The minimal inhibitory concentration of the antibacterial peptide against saccharomyces cerevisiae induced by microbroth dilution assay was 1.5 mg/L.2 Infection of mice with S.aureus successfully established a mouse mastitis pathology model.3 The muscarinic AMPs was used to treat the pathological model of staphylococcal mastitis in mice.The mammary glands of mice were collected on the 3^rd,5^th,and 7^thh days of treatment.The content of tumor cell factor?TNF-??and S.aureus in the mammary glands of mice was measured.?1?Determination of the number of S.aureus in mouse mammary gland tissue using a high-salt mannitol-differentiation medium,the results shown that treatment of S.aureus,the content is significantly lower than that of normal saline group?p<0.01?,illustrate bots antibacterial peptides can kill S.aureus in breast tissue.?2?HE staining used to prepare pathological tissue sections to showed that the fly larvae antibacterial peptides can reduce the damage of the mammary glands.?3?The content of TNF-?in mammary glands of mice detected by ELISA,the results shown that,compared with normal saline group,in the treatment of 3^rd,5^thh days breast tissue TNF-?content significantly lowered?p<0.01?,showed the bots antibacterial peptides to TNF-?has obvious inhibitory effect.?4?According to number of S.aureus in mice's breast tissue calculated the cure rate of each treatment group,the cure rate is 0 for normal saline treatment group,antibacterial peptide in treatment group was 40%,the antibiotics in the treatment group was 80%.In conslusion,the maggot AMPs have a certain therapeutic effect on mastitis of mice caused by S.aureus and have the potential to replace traditional antibiotics as novel therapeutic drugs,and also to cope with the abuse of antibiotics and bacterial drug resistance.The aspect provides a new direction,therefore,the fly larvae AMPs is expected to become a new type of antibacterial agent for the treatment of mastitis in cows,and provides a scientific basis and theoretical basis for the treatment of mastitis in dairy cows with fly locust AMPs.