Antibacterial peptide and application thereof

Abstract

The invention provides an antibacterial peptide and application thereof, and relates to the technical field of antibacterial peptides. The amino acid sequence of the antibacterial peptide disclosed by the invention is as shown in SEQ ID No. 1. When chick embryos are treated by adopting the antibacterial peptide disclosed by the invention, the capability of resisting avian pathogenic Escherichia coli infection of broiler chickens can be improved, the inflammatory response of APEC challenged chickens can be alleviated, the immune response of organisms can be regulated, the adhesion and colonization of avian pathogenic Escherichia coli in broiler chickens can be inhibited, and the antibacterial peptide also has extremely low hemolytic activity and can be used for preventing and treating the avian pathogenic Escherichia coli. The morbidity, death rate and lesion score can be obviously reduced, so that the survival rate of the broiler chicken is effectively improved, the growth of the broiler chicken is promoted, and the breeding benefit is increased. The invention provides a means beneficial to guaranteeing the quality safety and public health safety of poultry products for preventing and controlling broiler chicken colibacillosis, and meets the requirements of modern breeding industry on greenness, safety and high efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antibacterial peptides, and particularly relates to an antibacterial peptide and application thereof. BACKGROUND

[0002] Avian Pathogenic Escherichia coli (APEC) is one of the pathogenic bacteria that is extremely harmful in the poultry industry, which can cause various diseases in poultry, such as perihepatitis, air sacculitis, peritonitis, pericarditis, etc. The vertical transmission of APEC in breeding chicken flocks can lead to yolk sac infection and increase the mortality of chicks. At the same time, it also affects the growth of broilers and the egg production of laying hens, leading to an increase in poultry mortality and a decrease in production performance, which brings huge economic losses to the poultry industry. APEC has host specificity, and chicken, duck, goose and other birds are its main hosts. The pathogenic mechanism of APEC is complex, involving multiple virulence factors such as adhesion factors, biofilm formation factors, iron uptake systems, etc. These factors work together to enable APEC to colonize, invade and cause diseases in avian hosts. For example, its adhesion factors can specifically adhere to the surface of host cells, laying the foundation for subsequent invasion and infection; the formation of biofilm helps the bacteria to resist the attack of the host immune system and the adverse effects of the external environment, enhancing the survival ability and pathogenicity of the bacteria. In addition, APEC can also inject effector proteins into host cells through, such as type III secretion system, to interfere with the normal physiological function of host cells, further promoting the progress of infection. In recent years, with the widespread use of antibiotics, multiple drug-resistant APEC strains have emerged, which has brought challenges to the prevention and control of colibacillosis. In recent years, with the widespread use of antibiotics, multiple drug-resistant APEC strains have emerged, which has brought challenges to the prevention and control of colibacillosis, and the dependence on antibiotics in the traditional breeding process has also brought about the risk of drug resistance and drug residues due to the abuse of antibiotics, which does not meet the demand of modern breeding industry for green, safe and efficient.

[0003] Antibacterial peptides are a class of polypeptide compounds with antibacterial activity. Because of their high antibacterial capacity, unique bactericidal mechanism and difficulty in inducing pathogenic bacteria to develop drug resistance, they have become a new means of preventing and treating bacterial diseases and have shown broad application prospects in poultry breeding. Cathelicidins are a class of antibacterial peptides widely present in vertebrates and play a key and unique role in the innate immune system of chickens. Chicken cathelicidin has broad-spectrum antimicrobial activity and can effectively resist infection of various pathogenic microorganisms, including gram-positive bacteria, gram-negative bacteria, fungi and viruses. In terms of combating avian pathogenic E. coli disease, antibacterial peptide Cathelicidin-3 (CATH-3) has antibacterial effect, but its hemolytic activity is high, the selectivity to normal cells is poor, especially the red blood cell destruction ability is strong, and there is a safety risk. Therefore, it is urgent to develop an antibacterial peptide with significant inhibitory effect on APEC and no safety risk, which can effectively reduce the morbidity and mortality. SUMMARY

[0004] In view of the above technical problems, the first object of the present application is to provide an antibacterial peptide. The present application can improve the ability of broiler chicks to resist avian pathogenic E. coli infection by in ovo injection of antibacterial peptide as shown in SEQ ID No. 1, and has very low hemolytic activity. The present application provides an antibacterial peptide which can effectively reduce the morbidity and mortality and has no safety risk.

[0005] The second object of the present application is to provide a nucleic acid fragment.

[0006] The third object of the present application is to provide a recombinant expression vector.

[0007] The fourth object of the present application is to provide a recombinant engineering bacteria.

[0008] The fifth object of the present application is to provide the use of the above-mentioned antibacterial peptide in the preparation of a medicine for inhibiting avian pathogenic E. coli.

[0009] The sixth object of the present application is to provide the use of the above-mentioned antibacterial peptide in the preparation of a medicine for improving the survival rate of poultry caused by avian pathogenic E. coli.

[0010] The seventh object of the present application is to provide a medicine for inhibiting avian pathogenic E. coli.

[0011] To achieve the above-mentioned objects of the present application, the technical solutions of the present application are as follows:

[0012] The present application provides an antibacterial peptide, and the amino acid sequence of the antibacterial peptide is as shown in SEQ ID No. 1.

[0013] The present application provides a nucleic acid fragment for encoding the antibacterial peptide.

[0014] The present application provides a recombinant expression vector with the nucleic acid fragment inserted.

[0015] The present application provides a recombinant engineering bacteria with the recombinant expression vector inserted.

[0016] The present application provides the antibacterial peptide in the preparation of a drug for inhibiting avian pathogenic E. coli.

[0017] The present application provides the antibacterial peptide in the preparation of a drug for increasing the survival rate of poultry caused by avian pathogenic E. coli.

[0018] As an embodiment, the avian pathogenic E. coli is derived from any one or several of chicken, duck and goose.

[0019] The present application provides a drug for inhibiting avian pathogenic E. coli, which comprises the antibacterial peptide.

[0020] As an embodiment, the drug further comprises cholesterol.

[0021] As an embodiment, the concentration of the antibacterial peptide is 0.5-0.75 mg / mL.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] 1. The antibacterial peptide provided by the present application is rich in non-polar amino acids, has small molecular weight and simple structure, and does not contain disulfide bonds and cyclic structures, which is convenient for chemical synthesis and genetic engineering preparation.

[0024] 2. The present application can improve the ability of broiler chicks to resist avian pathogenic E. coli infection by treating chicken embryos with the antibacterial peptide in the late incubation period, not only can reduce the inflammatory response of APEC infected chickens, but also can regulate the immune response of the body, inhibit the adhesion and colonization of bacteria in the body of broilers, significantly reduce the morbidity, mortality and lesion score, thereby effectively improving the survival rate of broilers, promoting the growth of broilers and increasing the breeding benefit. Moreover, the antibacterial peptide treatment has very low hemolytic activity, compared with antibacterial peptide CATH-3, not only significantly improves the ability to resist APEC infection, but also makes the hemolytic activity decrease by more than 10 times.

[0025] 3. The antibacterial peptide provides a new means for preventing and controlling E. coli disease in broiler chickens, helps to reduce the dependence on antibiotics in traditional breeding process, reduces the risk of drug resistance and drug residue problems caused by antibiotic abuse, meets the demand of modern breeding industry for green, safe and efficient, and is conducive to ensuring the quality and safety of poultry products and public health safety. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Survival, lesions and air sac bacterial load results of 7-day-old broiler chickens hatched after in ovo injection of different doses of antibacterial peptide 60 after challenge with APEC E058 strain, wherein A is survival rate, B is lesion score, and C is air sac bacterial load;

[0027] Figure 2 Survival and lesions of 7-day-old broiler chickens hatched after in ovo injection of antibacterial peptide after challenge with APEC E058 strain, wherein A is survival rate, B is lesion score, and C is air sac bacterial load;

[0028] Figure 3 Bacterial load results of different organs of 7-day-old broiler chickens hatched after in ovo injection of antibacterial peptide 60 after challenge with APEC E058 strain, wherein A is heart bacterial load at different time points after challenge, B is liver bacterial load at different time points after challenge, C is spleen bacterial load at different time points after challenge, D is lung bacterial load at different time points after challenge, and E is kidney bacterial load at different time points after challenge, and in the figure, Mock in the horizontal coordinate label represents the healthy control group, X represents the challenge group, and 60 represents the antibacterial peptide 60 group. DETAILED DESCRIPTION

[0029] The application provides an antibacterial peptide, and an amino acid sequence of the antibacterial peptide is shown as SEQ ID No. 1. The amino acid sequence of SEQ ID No. 1 is Pro-Val-Arg-Val-Lys-Arg-Phe-Trp-Pro-Leu-Val-Pro-Val-Ala-Ile-Asn-Thr-Val-Ile-Ala-Gly-Ile-Asn-Leu-Tyr-Lys-Ala-Ile-Arg-Arg-Lys (PVRVKRFWPLVPVAINTVIAGINLYKAIRRK). Based on the antibacterial peptide CAT H-3, which is a peptide segment with antibacterial activity, a plurality of derivative peptides are designed and synthesized through in-depth research and optimization, and the antibacterial peptide shown as the sequence SEQ ID No. 1 (referred to as No. 60 antibacterial peptide) is screened. The No. 60 antibacterial peptide is delivered to a chicken embryo allantoic cavity, and is settled and absorbed into the body of the chicken embryo. The No. 60 antibacterial peptide of the application gives the broiler chicken stronger resistance to APEC infection, and the hemolytic activity is reduced by more than 10 times, and the safety is significantly improved compared with the antibacterial peptide CATH-3. The antibacterial peptide of the application can be prepared by chemical synthesis or genetic engineering.

[0030] The application also provides a nucleic acid fragment for encoding the antibacterial peptide. In the application, the sequence of the nucleic acid fragment is not specifically limited, and the nucleic acid fragment can encode the antibacterial peptide. The application also provides a recombinant expression vector, and the nucleic acid fragment for encoding the antibacterial peptide is inserted into the expression vector. In the application, the nucleic acid fragment for encoding the antibacterial peptide shown as SEQ ID No. 1 is inserted into the expression vector. As an optional embodiment, the expression vector includes a pET-32a vector, a pGEX-4T-1 vector, a pYES2 vector or a pPIC9K vector.

[0031] The application also provides a recombinant engineering bacterium, and the recombinant engineering bacterium contains the recombinant expression vector.

[0032] Based on the resistance of the No. 60 antibacterial peptide to APEC infection and the safety, the application can also use the antibacterial peptide to prepare a medicine for inhibiting avian pathogenic Escherichia coli. The application can resist various diseases caused by avian pathogenic Escherichia coli, including perihepatitis, air sac inflammation, peritonitis and pericarditis. In the application, the avian pathogenic Escherichia coli is derived from one or more of chickens, ducks and geese.

[0033] Based on the fact that the No. 60 antibacterial peptide can effectively produce an immune response when encountering APEC infection, and reduce the morbidity and mortality, the application also provides the antibacterial peptide for preparing a medicine for improving the survival rate of poultry caused by avian pathogenic Escherichia coli.

[0034] The present application also provides a medicine for inhibiting avian pathogenic E. coli, which comprises the antibacterial peptide as described above. In the present application, the concentration of the antibacterial peptide is 0.5-0.75 mg / mL. In the present application, the medicine further comprises cholesterol, which has the effect of promoting the precipitation and absorption of the antibacterial peptide No. 60, and can promote the effective absorption of the antibacterial peptide No. 60 into the embryo of the avian, without adversely affecting the normal development of the embryo, so that the avian has the ability to resist APEC infection as soon as it hatches, and provides a guarantee for its healthy growth and development. As an embodiment, the concentration of the cholesterol is 0.05-0.2 mg / mL. In the present application, the cholesterol solution is prepared with anhydrous ethanol as the solvent, and the medicine further comprises 1.0-2.0 mM of sodium dihydrogen phosphate dihydrate, 7-9 mM of disodium hydrogen phosphate dodecahydrate, and 10-30 mM of sodium chloride. In the present application, the pH value of the medicine is controlled at 7.0-7.5.

[0035] In the present application, the preparation method of the medicine comprises the following steps: preparing 0.05-0.2 mg / mL of a cholesterol solution with anhydrous ethanol as component 1, dissolving 1.0-2.0 mM of sodium dihydrogen phosphate dihydrate, 7-9 mM of disodium hydrogen phosphate dodecahydrate, and 10-30 mM of sodium chloride in water as component 2, mixing component 1 and component 2 to obtain an injection buffer, dissolving the antibacterial peptide No. 60 in the injection buffer to a final concentration of 0.5-0.75 mg / mL, and oscillating for 10-15 min to obtain the antibacterial peptide No. 60 preparation.

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0037] In the following examples, the materials and reagents used, unless otherwise specified, can be obtained from commercial channels, such as the reagents and consumables involved in the present application.

[0038] Example 1 Synthesis and screening of derivative peptides

[0039] The present application is based on CATH-3, a peptide segment with antibacterial activity, through in-depth research and optimization, a variety of derivative peptides are designed and synthesized, and a derivative peptide Ch-Pb-CATH3-60 (hereinafter referred to as No. 60 antibacterial peptide) is screened and obtained, and the amino acid sequence is shown in SEQ ID No. 1: Pro-Val-Arg-Val-Lys-Arg-Phe-Trp-Pro-Leu-Val-Pro-Val-Ala-Ile-Asn-Thr-Val-Ile-Ala-Gly-Ile-Asn-Leu-Tyr-Lys-Ala-Ile-Arg-Arg-Lys.

[0040] Example 2

[0041] A 2mg / mL cholesterol stock solution was prepared using anhydrous ethanol and filtered to remove bacteria as component 1, 1.48mM sodium dihydrogen phosphate dihydrate, 8.06mM disodium hydrogen phosphate dodecahydrate, 20mM sodium chloride were prepared in sterile ultrapure water and filtered to remove bacteria as component 2, the component 1 cholesterol stock solution was added to component 2 at 5% by volume, and the component 2 was kept fully vortexed during the addition process to obtain an injection buffer. The synthesized No. 60 antibacterial peptide powder was accurately weighed and dissolved in the above injection buffer to a final concentration of 0.5mg / mL, pH 7.27, and fully oscillated on a vortex oscillator for 10 minutes until it was completely dissolved and uniform to obtain a stable No. 60 antibacterial peptide preparation.

[0042] Example 3

[0043] A 2mg / mL cholesterol stock solution was prepared using anhydrous ethanol and filtered to remove bacteria as component 1, 1.48mM sodium dihydrogen phosphate dihydrate, 8.06mM disodium hydrogen phosphate dodecahydrate, 20mM sodium chloride were prepared in sterile ultrapure water and filtered to remove bacteria as component 2, the component 1 cholesterol stock solution was added to component 2 at 5% by volume, and the component 2 was kept fully vortexed during the addition process to obtain an injection buffer. The synthesized No. 60 antibacterial peptide powder was accurately weighed and dissolved in the above injection buffer to a final concentration of 0.5mg / mL, pH 7.27, and fully oscillated on a vortex oscillator for 10 minutes until it was completely dissolved and uniform to obtain a stable No. 60 antibacterial peptide preparation.

[0044] Example 4

[0045] A 2 mg / mL cholesterol stock solution was prepared using anhydrous ethanol and filtered sterilized to obtain component 1. 1.97 mM sodium dihydrogen phosphate dihydrate, 9.01 mM disodium hydrogen phosphate dodecahydrate, and 30 mM sodium chloride were dissolved in sterile ultrapure water and filtered sterilized to obtain component 2. The cholesterol stock solution from component 1 was aseptically added to component 2 at an 8% (v / v) ratio, while vortexing component 2 thoroughly to obtain an injection buffer. The synthesized antimicrobial peptide No. 60 powder was accurately weighed and dissolved in the above injection buffer to a final concentration of 0.6 mg / mL, pH 7.27. The solution was vortexed thoroughly for 15 minutes until completely dissolved and homogeneous to obtain a stable antimicrobial peptide No. 60 formulation.

[0046] Comparative Example 1

[0047] The difference from Example 2 is that antimicrobial peptide No. 60 was replaced with antimicrobial peptide CATH-3 to prepare the CATH-3 antimicrobial peptide formulation; all other steps are the same.

[0048] Experimental Example 1: Hemolytic Concentration of Antimicrobial Peptides

[0049] Hemolytic activity is a qualitative description of the ability to hemolyze, while hemolytic concentration can indicate the strength of this ability. Lower hemolytic activity means that a higher hemolytic concentration is required to induce hemolysis.

[0050] Collect 5 mL of fresh broiler blood (from the distal subwing vein) using a heparinized biochemical tube (anticoagulant tube). Mix well and centrifuge at 3000×g at 4℃ for 10 min. Discard the supernatant. Wash the red blood cells three times with PBS, centrifuge at 3000×g at 4℃ for 10 min, discard the supernatant, and resuspend the red blood cells in PBS at a concentration of 4%. Add 100 μL of the resuspended red blood cells to a 96-well plate.

[0051] Antimicrobial peptide No. 60 and CATH-3 antimicrobial peptide from Example 1 were diluted with PBS. 100 μL of each peptide at different concentrations was added to a 96-well plate and mixed thoroughly to achieve final concentrations of 1 mg / mL, 0.25 mg / mL, 0.0625 mg / mL, 0.0156 mg / mL, and 0.0039 mg / mL, respectively. The total volume was 200 μL per well. PBS was used as a negative control, and 0.1% Triton X-100 (diluted with PBS) was used as a positive control. The plates were incubated at 37°C for 1 h. The mixture was then centrifuged at 3000×g at 4°C for 10 min. 100 μL of the supernatant was then used to read the OD value using a microplate reader. 450 The absorbance was measured at nm. According to the formula: Haemolysis (%) = (A p -A0 / A 100 Calculate the percentage of hemolysis at each concentration using (-A0)×100 (where A... pA0 is the absorbance value of the experimental group, and A0 is the absorbance value of the negative control. 100 (The absorbance value is for the positive control). Then, based on the concentration of the antimicrobial peptide and the percentage of hemolysis in each well, the half-hemolytic concentration (50% Hemolytic Concentration, HC) is calculated using SPSS regression algorithm. 50 The results are shown in Table 1.

[0052] Table 1. Results of determination of hemolytic concentration of CATH-3 and antimicrobial peptide No. 60

[0053]

[0054] As shown in Table 1, compared to CATH3, antimicrobial peptide No. 60 exhibits a significantly higher hemolytic concentration in chicken erythrocytes, increasing by 17.8 times. This indicates that the hemolytic activity of antimicrobial peptide No. 60 in this invention is reduced by more than 10 times, and at the same concentration, antimicrobial peptide No. 60 demonstrates better safety, resulting in a significant improvement in safety for use.

[0055] Experimental Example 2: Survival, lesions, and air sac bacterial load of 7-day-old broilers hatched after intraembryonic injection of different doses of antimicrobial peptide No. 60 and challenged with APEC E058 strain.

[0056] Two hundred and fifty broiler chicken embryos, three days before hatching (18-day embryonic age), were randomly divided into five groups: an intraembryonic injection group (0.5 mg / kg egg weight), an intraembryonic injection group (1.0 mg / kg egg weight), an intraembryonic injection group (1.5 mg / kg egg weight), a healthy control group, and a challenge control group. The antimicrobial peptide preparation No. 60 from Example 2 was injected into the allantoic cavity of the embryo at concentrations of 0.5, 1.0, and 1.5 mg / kg egg weight, respectively. The healthy control group and the challenge control group were injected with the same volume of intraembryonic injection buffer. All five groups were then incubated under the same conditions until hatching.

[0057] Seven days after hatching, use APEC E058 strain at a rate of 1×10 6 Chickens were challenged with CFU / feather via air sac injection in the 0.5 mg / kg egg weight intraembryonic injection group, the 1.0 mg / kg egg weight intraembryonic injection group, the 1.5 mg / kg egg weight intraembryonic injection group, and the challenge control group. Observation continued until 14 days post-challenge. Mortality was recorded in each group, and serum was collected from surviving chickens 14 days post-challenge. Euthanasia and necropsy were performed, and lesion scores were recorded. Air sac lavage fluid was collected and plated on MacConkey agar plates for APEC counting. Experimental results are as follows: Figure 1As shown, the protection rate of broilers after challenge with the virus in the 0.5 mg / kg egg weight intraembryonic injection group was lower than that in the 1.0 mg / kg egg weight intraembryonic injection groups and the 1.5 mg / kg egg weight intraembryonic injection groups. The survival rate of the 1.0 mg / kg egg weight intraembryonic injection group was over 90% after 7 days of challenge and over 75% after 14 days. The protective effect of the 1.0 mg / kg egg weight intraembryonic injection group was comparable to, and slightly better than, that of the 1.5 mg / kg egg weight intraembryonic injection group. Therefore, the effective dose range for antimicrobial peptide No. 60 injection is 1–1.5 mg / kg egg weight, with 1 mg / kg egg weight being optimal.

[0058] In Experiment 3, the survival rate and lesion score of 7-day-old broilers hatched after intraembryonic injection of antimicrobial peptides were challenged with APEC strain E058.

[0059] Two hundred broiler chicken embryos were collected three days before hatching (18 embryonic ages) and randomly divided into four groups: a CATH-3 treatment group, a Ch-Pb-CATH3-60 treatment group, a healthy control group, and a challenge control group. The antimicrobial peptide preparation No. 60 from Example 2 and the CATH-3 antimicrobial peptide preparation from Comparative Example 1 were injected into the allantoic cavity of the chicken embryos via intraembryonic injection. The concentrations of antimicrobial peptide No. 60 and CATH-3 were 1 mg / kg egg weight, respectively. The healthy control group and the challenge control group were injected with the same volume of intraembryonic injection buffer. All four groups were then incubated under the same conditions until hatching.

[0060] Seven days after hatching, use APEC E058 strain at a rate of 1×10 6 Chickens in the CATH-3 treatment group, Ch-Pb-CATH3-60 treatment group, and the challenge control group were challenged with CFU / feather via air sac injection. Observation continued for 7 days post-challenge, and mortality was recorded for each group. Serum from surviving chickens was collected 7 days post-challenge. After euthanasia and necropsy, lesion scores were recorded. Air sac lavage fluid was collected and plated on MacConkey agar plates for APEC counting. Experimental results are as follows: Figure 2 As shown, compared with CATH-3, the No. 60 antimicrobial peptide group reduced mortality by 5%, decreased organ lesion scores after infection (mean lesion score of 3.77 in the challenge control group, 3.18 in the CATH-3 group, and 2.58 in the No. 60 antimicrobial peptide group), and reduced air sac bacterial load (mean air sac bacterial load of 10 in the challenge control group). 1.73 The average lesion score in the CATH-3 group was 10. 1.52 The average lesion score of the No. 60 antimicrobial peptide group was 10. 1.26 ).

[0061] In Experiment 460, 7-day-old broilers hatched after intraembryonic injection of antimicrobial peptide were challenged with APEC strain E058. The bacterial load in different organs of these broilers was measured.

[0062] One hundred and fifty broiler chicken embryos, three days before hatching (18 embryonic ages), were randomly divided into three groups: a Ch-Pb-CATH3-60 treatment group, a healthy control group, and a challenge control group. The antimicrobial peptide preparation No. 60 from Example 2 was delivered into the allantoic cavity of the chicken embryos via intraembryonic injection. The injection concentration of antimicrobial peptide No. 60 was 1 mg / kg egg weight. The healthy control group and the challenge control group were injected with the same volume of intraembryonic injection buffer. All three groups were then incubated under the same conditions until hatching.

[0063] On day 7 after hatching, use APEC E058 strain at a rate of 1×10 6 Chickens in the Ch-Pb-CATH3-60 treatment group and the challenge control group were challenged with CFU / feather via air sac injection. At 6h, 12h, 24h, 48h, and 72h post-challenge, heart, liver, spleen, lung, and kidney organs were collected for plate counts to monitor the dynamic distribution of APEC E058 strain in broilers. The experimental results are as follows: Figure 3 As shown, at the same time point after challenge, the bacterial load in different organs of the Ch-Pb-CATH3-60 treatment group was slightly lower than that of the challenge control group, indicating that intraembryonic injection of antimicrobial peptide No. 60 can reduce the bacterial load in organs after infection with Escherichia coli APEC E058 to a certain extent, thereby achieving a certain protective effect.

[0064] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An antimicrobial peptide, characterized in that, The amino acid sequence of the antimicrobial peptide is shown in SEQ ID No.

1.

2. A nucleic acid fragment, characterized in that, The nucleic acid fragment is used to encode the antimicrobial peptide of claim 1.

3. A recombinant expression vector, characterized in that, The nucleic acid fragment of claim 2 is inserted into the recombinant expression vector.

4. A recombinant engineered bacterium, characterized in that, The recombinant engineered bacteria contain the recombinant expression vector as described in claim 3.

5. The use of the antimicrobial peptide according to claim 1 in the preparation of a drug for inhibiting pathogenic avian Escherichia coli.

6. The use of the antimicrobial peptide according to claim 1 in the preparation of a drug for improving the survival rate of poultry caused by pathogenic Escherichia coli.

7. The application according to claim 5 or 6, characterized in that, The pathogenic Escherichia coli in birds comes from any one or more of chickens, ducks, and geese.

8. A drug for inhibiting pathogenic Escherichia coli in birds, characterized in that, The drug includes the antimicrobial peptide as described in claim 1.

9. The medicament according to claim 8, characterized in that, The medication also includes cholesterol.

10. The medicament according to claim 8, characterized in that, The concentration of the antimicrobial peptide is 0.5–0.75 mg / mL.

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