Phage composition for preventing and treating salmonella abortus of horses, biological preparation and application of bacteriophage composition and biological preparation

Abstract

The invention belongs to the technical field of biology, and particularly relates to a bacteriophage composition for preventing and treating horse salmonella abortus, a biological preparation and application of the bacteriophage composition and the biological preparation. The bacteriophage composition comprises a bacteriophage 4FS1, a bacteriophage DS-BP2 and a bacteriophage DS2; the preservation number of the bacteriophage 4FS1 is CCTCC (China Center For Type Culture Collection) NO: M 20242020; the preservation number of the bacteriophage DS-BP2 is CCTCC (China Center For Type Culture Collection) NO: M 202402021; the preservation number of the bacteriophage DS2 is CGMCC (China General Microbiological Culture Collection Center Three kinds of virulent bacteriophages 4FS1, DS-BP2 and DS2 aiming at different host spectrums of salmonella are separated and screened, the three kinds of virulent bacteriophages 4FS1, DS-BP2 and DS2 are combined into the bacteriophage cocktail, the occurrence of bacteriophage-tolerant strains can be effectively prevented or delayed, and the screened bacteriophages have a synergistic interaction effect; the three bacteriophages obtained by separation can be independently used or combined into a bacteriophage cocktail for preventing or treating infection caused by horse abortion salmonella, such as female donkey abortion and the like.

Description

Technical Field

[0001] The invention belongs to the field of biotechnology, and in particular relates to a bacteriophage composition for preventing and treating equine abortion salmonella, a biological preparation and application thereof. Background Art

[0002] There are many serotypes of Salmonella, most of which are pathogenic and have a wide host spectrum, including mammals, birds and humans. However, different serotypes of Salmonella infect different hosts. Among them, Salmonella equi abortion mainly infects equine animals. Donkey paratyphoid is an infectious disease of equine animals mainly caused by Salmonella equi abortion, characterized by abortion of pregnant donkeys. The main characteristics are abortion of female donkeys, sepsis of newborn foals and polyarthritis. First-time pregnant female donkeys and newborn foals are the most susceptible. If not treated in time, it can lead to secondary infection, accompanied by severe metritis, including purulent and foul-smelling bloody vaginal discharge. This metritis may last for a long time, leading to repeated infertility or frequent abortions.

[0003] So far, all approved antibiotic classes, whether natural, semi-synthetic or synthetic compounds, have developed resistance in at least some of the pathogens they target. There are few antibiotics available for clinical use, so it is urgent to develop effective antibiotic alternatives to overcome the antibiotic resistance crisis.

[0004] Bacteriophages are widely present in nature. They are a type of virus that mainly infects bacteria and are natural predators of bacteria. Compared with antibiotics, phages have the advantages of high lysis efficiency, strong specificity, few side effects, no damage to the host's normal microbiome, and low production cost. A single phage can easily produce phage-resistant strains during its interaction with bacteria. Therefore, seeking a phage combination with different host spectra and the ability to broaden the lysis spectrum has become an urgent problem to be solved. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a phage composition for preventing and treating equine abortion Salmonella that has a wide lysis spectrum, is not prone to produce phage-resistant strains, and has obvious synergistic lysis effect.

[0006] Another object of the present invention is to provide a biological preparation containing the above-mentioned bacteriophage composition.

[0007] The present invention also provides the use of the bacteriophage composition and biological preparation in preventing and treating equine abortion Salmonella.

[0008] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The invention provides a bacteriophage composition for preventing and treating equine abortion salmonella. The bacteriophage composition comprises two or more of bacteriophage 4FS1, bacteriophage DS-BP2 and bacteriophage DS2; the deposit number of the bacteriophage 4FS1 is CCTCC NO: M 20242020; the deposit number of the bacteriophage DS-BP2 is CCTCC NO: M 202402021; the deposit number of the bacteriophage DS2 is CGMCC No.17093.

[0009] Furthermore, the total content of bacteriophages in the bacteriophage composition is 10 8 -10 10 PFU / mL.

[0010] Furthermore, the mass ratio of the bacteriophage 4FS1, bacteriophage DS-BP2 and bacteriophage DS2 is 1:1:1.

[0011] The present invention also provides the use of the bacteriophage composition in preparing a product for preventing and treating equine abortion Salmonella infection.

[0012] Furthermore, in the phage composition, the multiplicity of infection of phage 4FS1 is 0.001-0.1; the multiplicity of infection of phage DS-BP2 is 0.01-0.1; and the multiplicity of infection of phage DS2 is 0.001-0.01.

[0013] Another object of the present invention is to provide a biological preparation for preventing and treating equine abortion Salmonella infection containing the above-mentioned bacteriophage composition.

[0014] The biological preparation provided by the present invention is in any veterinary acceptable dosage form; preferably, the preparation is a liquid dosage form.

[0015] The present invention also provides the use of the biological preparation in preparing medicine for preventing and treating equine abortion Salmonella infection.

[0016] Preferably, the incubation periods of the phage composition, phage 4FS1, phage DS-BP2, and phage DS2 are 20 min, 15 min, and 5 min, respectively, and all three last until 120 min to reach a plateau phase.

[0017] Preferably, in the phage composition, the pH value at which the activity of phage 4FS1 is stable is 4-11; the pH value at which the activity of phage DS-BP2 is stable is 4-10; and the pH value at which the activity of phage DS2 is stable is 4-12.

[0018] Preferably, in the phage composition, the temperature at which the activities of phages 4FS1, DS-BP2 and DS2 are stable is no higher than 70°C.

[0019] Beneficial effects of the present invention: (1) The present invention isolates and screens three virulent phages 4FS1, DS-BP2, and DS2 targeting different host spectra of Salmonella. Combining them into a phage cocktail can effectively prevent or delay the emergence of phage-tolerant strains, and the phages screened by the present invention have a synergistic effect; (2) The three phages isolated and obtained by the present invention are all broad-spectrum phages. In addition to lysing Salmonella abortus, they can also lyse serotypes of Salmonella such as Salmonella Enteritidis and Salmonella Typhimurium. They have high efficient lysis activity and have good lysis effects under different multiplicity of infection (MOI). They have good temperature tolerance and acid-base tolerance and have a wide range of applicability in practical production applications.

[0020] (3) The three phages isolated and obtained by the present invention can be used alone or combined into a phage cocktail, which can be used to prevent or treat infections caused by Salmonella enterica equine abortion, such as abortion in donkeys.

[0021] Collection information 1 Biological materials: Bacteriophage (phage) 4FS1 Salmonella phage 4FS1 Storage time: November 4, 2024, Collection Unit: China Center for Type Culture Collection, Deposit number: CCTCC NO: M 20242421, Address of the collection unit: Wuhan University Collection Center, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0022] Collection information 2 Biomaterial: Phage DS-BP2 Salmonella phage DS-BP2 Storage time: November 4, 2024, Collection Unit: China Center for Type Culture Collection, Deposit number: CCTCC NO: M 20242420, Address of the collection unit: Wuhan University Collection Center, No. 299, Bayi Road, Wuchang District, Wuhan City, Hubei Province.

[0023] Collection information 3 Biological material: bacteriophage DS2 Storage time: January 18, 2019 Depository: General Microbiology Center, China Microbiological Culture Collection Administration, Deposit number: CGMCC No.17093, Address of the depository: Institute of Microbiology, Chinese Academy of Sciences, No. 3, Yard 1, Beichen West Road, Chaoyang District, Beijing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Transmission electron microscopic morphology of the three phages screened for the present invention; Figure 2 The plaque morphology of three phages on double-layer plates; Figure 3 The best MOI diagram of the three phages screened in the present invention; Figure 4 One-step growth curves of three phages; Figure 5 pH stability of the three phages; Figure 6 Thermostability of the three phages; Figure 7 UV stability of three bacteriophages; Figure 8 Phage in vitro lysis curve; ***: P<0.001; Fig. 9 Detection results of bacterial load in four tissues; ***: P < 0.001, **: P < 0.01, *: P < 0.05; Fig.10 Phage titers of four tissues; **: P < 0.01, *: P < 0.05. DETAILED DESCRIPTION

[0025] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0026] The invention provides a Salmonella phage composition. The phage composition comprises at least one of phage 4FS1, phage DS-BP2 and phage DS2; the phage 4FS1 has a deposit number of CCTCC NO: M20242421, the phage DS-BP2 has a deposit number of CCTCC NO: M20242420, and the phage DS2 has a deposit number of CGMCC No.17093.

[0027] In the present invention, bacteriophage 4FS1, bacteriophage DS-BP2 and bacteriophage DS2 are obtained by separation of donkey farm feces and sewage. Bacteriophage 4FS1 and bacteriophage DS-BP2 were deposited in the China Center for Type Culture Collection on January 20, 2024, and bacteriophage DS2 was deposited in the General Microbiology Center of China National Microbiological Culture Collection on January 18, 2019. The phage composition provided by the present invention can effectively prevent or delay the emergence of phage-tolerant strains, and the synergistic effect is obvious. The present invention has no special limitation on the dosage ratio of the above-mentioned various phages, and any ratio can be adopted, preferably an equal ratio. In the present invention, the total content of phages in the phage composition is preferably 10 8 PFU / mL-10 10 PFU / mL, more preferably 10 9 In the present invention, the Salmonella phage composition is preferably any combination of two of phage 4FS1, phage DS-BP2 and phage DS2, and more preferably a combination of three of phage 4FS1, phage DS-BP2 and phage DS2.

[0028] The present invention also provides an application of the bacteriophage composition in preparing a product for preventing and treating Salmonella infection.

[0029] The phage composition of the present invention has a wide lysis spectrum, and in addition to lysing equine abortion Salmonella, it can also lyse various serotypes of Salmonella such as Enteritidis and Salmonella typhimurium.

[0030] In the phage composition of the present invention, the multiplicity of infection of phage 4FS1 is preferably 0.001-0.1, more preferably 0.01; the multiplicity of infection of phage DS-BP2 is preferably 0.1-0.01, more preferably 0.1; the multiplicity of infection of phage DS2 is preferably 0.001-0.01, more preferably 0.01.

[0031] In the phage composition of the present invention, the incubation periods of phage 4FS1, phage DS-BP2, and phage DS2 are 20 min, 15 min, and 5 min, respectively, and all of them last until 120 min to reach a plateau phase.

[0032] In the phage composition of the present invention, the pH value at which the activity of phage 4FS1 is stable is 4-11; the pH value at which the activity of phage DS-BP2 is stable is 4-10, and the pH value at which the activity of phage DS2 is stable is 4-12. In the phage composition of the present invention, the temperature at which the activity of phage 4FS1, DS-BP2, and DS2 is stable is no higher than 70°C. In the phage composition of the present invention, phage 4FS1, DS-BP2, and DS2 can still maintain a relatively high titer after 40 minutes of ultraviolet irradiation.

[0033] The present invention also provides a biological preparation for preventing and treating Salmonella infection, wherein the biological preparation comprises the above-mentioned equine abortion Salmonella phage composition.

[0034] In the biological preparation of the present invention, the titer of the above-mentioned Salmonella abortus phage composition is preferably 10 8 PFU / mL-10 10 PFU / mL, more preferably 10 9 PFU / mL.

[0035] In the present invention, the biological preparation can be in any veterinary acceptable dosage form; preferably, the biological preparation is a liquid dosage form.

[0036] Example 1 (1) Isolation of bacteriophage: Feces and sewage samples were collected from donkey farms in different areas of Shandong Province. The host bacteria of the isolated phage was Salmonella equi abortion S1, which was isolated and preserved from aborted donkey fetuses by our laboratory.

[0037] The collected sewage was initially filtered with filter paper to remove large solid impurities. 20 mL of the filtered sewage sample was taken out and placed in a 50 mL centrifuge tube. It was centrifuged at 10,000 g for 10 min. The supernatant was filtered with a 0.45 μm pore size sterile filter as the mother liquid for phage proliferation and stored at 4°C for later use.

[0038] Inoculate equine abortion Salmonella S1 in LB medium, shake culture at 37℃ until the logarithmic growth phase, take 10mL of filtered supernatant, 5mL of host bacteria and 20mL of LB medium, shake culture at 37℃ 220r for 12h, so that the phage in the fecal filtrate can fully proliferate. Centrifuge the cultured sample at 12000g for 3min, take the supernatant, filter it with a 0.22μm sterile filter, and this filtrate is the phage stock solution. Confirm the presence of phage in the supernatant by spot analysis, take 3mL of melted semi-solid culture medium, add 100μl of host bacteria and mix evenly, pour into an ordinary LB solid culture dish, wait for it to solidify, take 20μl of phage stock solution and drop it on the poured double-layer plate, wait for it to solidify and put it into a 37℃ constant temperature incubator to observe whether plaques appear. The filtrate with plaques was diluted appropriately in gradients, 100 μl of the diluted liquid and 100 μl of the host bacteria were added to 3 mL of semi-solid culture medium, poured onto NA solid culture medium, spread flat, and inverted culture at 37°C for 8 h after solidification.

[0039] (2) Phage purification Pick up the plaque with a small gun tip, add it to 1mL of physiological saline, shake it on a shaker for 5 minutes, perform appropriate gradient dilution, take 100μl of the diluted phage solution and mix it with 100μl of host bacteria, add it to the melted semi-solid culture medium, pour it on the LB solid culture medium, culture it at 37℃ for 8h, and observe the appearance of single plaques. Repeat the operation at least 3 times to purify the phage.

[0040] The LB liquid culture medium: weigh 25 g of commercial LB culture medium powder (product of Qingdao Haibo Biotechnology Co., Ltd.), dissolve it in 1 L of distilled water, sterilize it by high pressure at 121° C. for 20 min, and refrigerate it at 4° C. for later use.

[0041] The NA solid culture medium: weigh 33 g of commercial NA culture medium powder (product of Qingdao Haibo Biotechnology Co., Ltd.), dissolve it in 1 L of distilled water, sterilize it under high pressure at 121° C. for 20 min, cool it to about 45° C., pour it into a sterile plate, and refrigerate it at 4° C. for later use.

[0042] The semi-solid culture medium is as follows: 7.5 g agar powder is added to 1 L of LB liquid culture medium, sterilized by high pressure at 121° C. for 20 min, stored at 4° C. after packaging, and heated to melt completely before use.

[0043] (3) Phage proliferation In order to increase the number of phages per unit volume, a liquid amplification method was used. The single plaque purified in step (2) was taken and placed in 1 mL of nutrient broth culture medium. The culture was incubated in a 37°C water bath for 10 min, and then centrifuged at 10,000 r / min for 5 min. 100 μl of the supernatant was taken and added to 5 mL of sterile nutrient broth liquid culture medium with 100 μl of Salmonella abortus equi. The culture was incubated at 37°C in a constant temperature shaker at 220 r / min for 4 h. When the mixed solution becomes clear, a phage proliferation solution was obtained. The supernatant was filtered through a 0.22 μm pore size sterile filter, and after 10-fold gradient dilution, the phage titer was determined using the double-layer plate method. According to the growth of different phages, the phage supernatant can be diluted to different concentration gradients for preliminary experiments. The optimal growth ratio of the phage is calculated based on the phage titer and stored at 4°C for later use. After the phage is purified and amplified, the phage titer can reach 10 9 PFU / mL.

[0044] (4) Electron microscopic observation of bacteriophage morphology Using the phosphotungstic acid negative staining method, take a drop of purified high-titer phage droplet and absorb it on the copper mesh for 10 minutes, then dry the residual suspension, stain it with 2% phosphotungstic acid (PTA, 2% w / v) for 3 minutes, dry the copper mesh with an infrared lamp, and observe under a transmission electron microscope. All three phages are tailed phages. The results are as follows Figure 1As shown in the figure. The whole-genome sequencing results showed that phage 4FS1 belongs to the long-tailed phages of the genus Jerseyvirus, phage DS2 belongs to the long-tailed phages of the genus Epseptimavirus, and phage DS-BP2 belongs to the short-tailed phages of the genus Berlinvirus. None of them contain lysogenic genes, drug-resistant genes, and virulence genes.

[0045] Example 2 Mix 100 μL of the overnight culture of the bacteria in Example 1 with the semi-solid medium and pour it onto the LB solid medium to make a double-layer plate. Dilute the phage 10-fold gradient into different concentrations. Take 20 μL of the phage with different concentrations and spot it onto the double-layer plate. After drying, incubate it upside down in a 37 °C incubator for 8 h, and observe the formation of plaques formed by gradient dilution on the plate. The results are as Figure 2 shown. The three selected Salmonella phages grew well on the double-layer plate, clear and transparent. With gradient dilution, single plaques of phages could be observed finally. Obvious halos would appear around the plaques of phage 4FS1 and DS-BP2.

[0046] Example 3 The host range of the phage was determined by the spotting method. Different strains to be tested were cultured to the logarithmic growth phase. Take 100 μL of the overnight culture of the bacteria and add it to the semi-solid medium. After mixing evenly, pour it onto the NA solid medium and wait for it to solidify. Take 10 μL of the phage with different dilution factors (10 1 ~10 7 ) and spot it onto the double-layer plate. After drying, incubate it upside down in a 37 °C incubator for 8 h, observe the lysis of the phage on the test strains, and calculate the plaque-forming rate (EOP) of the phage. The results are shown in Table 1. Phages 4FS1, DS-BP2, and DS2 have a wide lysis spectrum and can infect 64.2% of the test strains with high infection efficiency.

[0047] Table 1 Phage lysis spectrum EOP refers to the ratio of virus particles that can form visible plaques. Salmonella abortus equi S1 was selected as the standard indicator bacterium to compare the ratio of the titer of the phage lysing different host bacteria to the indicator bacterium. +++ means EOP ≥ 0.5, ++ means 0.1 ≤ EOP < 0.5, + means 0.001 < EOP < 0.1, and - means EOP ≤ 0.001.

[0048] Example 4 For the host range of the phage, the host bacterium S1 was cultured to the logarithmic growth phase (OD 600 = 0.6), and the concentration of the bacterial solution was adjusted to 1 × 10 7CFU / mL. Then, different concentrations of phages were added at different MOI (phage / bacteria) ratios of 10, 1, 0.1, 0.01, and 0.001, and the culture was placed in a 37°C shaker for 4 hours. The culture solution was centrifuged at 12000g for 1 minute and then diluted in physiological saline in multiples. The phage titers corresponding to different MOIs were determined by the double-layer plate method. The experiment was repeated three times, and the phage / bacteria ratio that produced the highest titer was the optimal MOI. The results are shown in the figure. Figure 3 As shown, when the optimal MOI of 4FS1, DS-BP2, and DS2 phages were 0.01, 0.1, and 0.01, respectively, the titer of each phage reached the highest, so this value was the optimal MOI for each phage.

[0049] Example 5 Host bacteria S1 was cultured to the logarithmic growth phase (OD 600 =0.6), and the concentration of the bacterial solution was adjusted to 1×10 8 CFU / mL. The phage and host bacteria were mixed at an MOI of 10, and placed in a 37°C shaker for 10 minutes to allow the phage to fully adsorb to the host bacteria. After the mixture was centrifuged at 10,000g for 10 minutes, the supernatant was discarded, the precipitate was resuspended with the same volume of LB, centrifuged again and the supernatant was discarded, and the precipitate was washed repeatedly twice. Finally, the resuspension was placed in a 37°C shaker for oscillation culture, and samples were taken at regular intervals to test the phage titer until 240 minutes. The filtered phage solution was continuously diluted in physiological saline, and the phage titer corresponding to different times was determined by the double-layer plate method. The experiment was repeated three times. With the infection time as the horizontal axis and the phage titer as the vertical axis, a one-step growth curve of the phage-infected host bacteria was plotted. The results are shown in Figure 4 As shown, the incubation periods of phage 4FS1, phage DS-BP2, and phage DS2 were 20 min, 15 min, and 5 min, respectively, and all three lasted until 120 min to reach a plateau phase.

[0050] Example 6 Take 100 μL (1×10 9 PFU / mL) phages were placed in 1.5mL sterile EP tubes, and 900μL of SM buffer solutions with different pH values ​​(2-13) were added respectively. The titers were determined by double-layer plate method at 37℃ for 1, 2, and 3h. The experiment was repeated 3 times. Figure 5 As shown, 4FS1 phage is relatively stable at pH 4-11; DS-BP2 phage is relatively stable at pH 4-10; and DS2 phage is relatively stable at pH 4-12.

[0051] Take the phage suspension (10 9PFU / mL) and placed them in test tubes. Take 4 tubes at each temperature, 500 μL per tube. Place these test tubes in a water bath at 37°C, 40°C, 50°C, 60°C, 70°C and 80°C for 20 min, 40 min and 60 min, take one tube at each time point, aspirate 100 μL of the sample for continuous gradient dilution and immediately use the double-layer agar plate method to determine the effect of different temperatures on phage titer. The results are shown in Figure 6 As shown, the titers of phages 4FS1 and DS2 remained basically unchanged (>10 9 PFU / mL); DS-BP2 phage titer>10 at 50℃ water bath for 60min 6 PFU / mL or above.

[0052] Take 4 mL of phage proliferation solution (10 9 PFU / mL) were placed under ultraviolet light at a distance of 40 cm. Every 10 minutes, 200 μL of phage proliferation fluid was taken and the titer was measured by double-layer plate method. Figure 7 As shown in the figure, phages 4FS1, DS-BP2 and DS2 can still maintain 10 4 At titers above PFU / mL, phages 4FS1, DS-BP2, and DS2 had strong tolerance to UV within 30 min.

[0053] Example 7 Host bacteria S1 was cultured overnight, and the activated overnight bacterial solution was inoculated into a 96-well cell plate and shaken at 37°C (220r) until the early exponential phase (OD 600 =0.3-0.4), at this time, a single phage and different combinations of phages were added to each well, and the MOI was 1. The static culture was continued for 24 hours, and the changing trend of the single phage and different combinations of phages in lysing the host bacteria in vitro was detected. From the lysis curve ( Figure 8 ) It can be observed that the combination of the three phages can inhibit the growth of bacteria, and the OD 600 The value decreased by 0.7, and the synergistic effect was significant (P < 0.001).

[0054] Example 8 Sixty mice aged about 6 weeks were randomly divided into 6 groups, with 10 mice in each group. The bacteria cultured to the logarithmic growth phase were diluted into 10 7 CFU / mL, 200 μL was inoculated by intraperitoneal injection. 24, 48, and 72 h after bacterial infection, the mice were euthanized, and the liver, spleen, lung, and uterus were removed to detect the bacterial load and phage titer of the tissues.

[0055] Bacteria challenge group: mice were intraperitoneally injected with PBS 1 hour after infection with bacteria, serving as the positive control group; The phage treatment groups were divided into single phage treatment group and phage cocktail treatment group: single phage treatment group: mice were intraperitoneally injected with 200 μL of three single phages (10 8 Phage cocktail treatment group: mice were intraperitoneally injected with 200 μL of phage cocktail (10 8 PFU / mL).

[0056] The PBS control group of healthy mice was intraperitoneally injected with PBS throughout the whole process as a control.

[0057] The results are as follows Fig. 9 As shown in the figure, both the single phage treatment group and the phage cocktail treatment group could reduce the bacterial load in each tissue, among which the phage cocktail group reduced the bacterial load in tissues more significantly. In each tissue 72 hours after the virus attack, the bacterial load in the cocktail group was reduced by 2-6 levels compared with the virus attack group (P < 0.05); Fig.10 As shown, the phage titer in the tissue was also the highest in the cocktail phage group.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A bacteriophage composition for preventing and treating Salmonella abortus in horses, characterized in that: The phage composition comprises two or more of phage 4FS1, phage DS-BP2 and phage DS2; the deposit number of the phage 4FS1 is CCTCC NO: M 20242020; the deposit number of the phage DS-BP2 is CCTCC NO: M 202402021; the deposit number of the phage DS2 is CGMCC No.17093.

2. The bacteriophage composition according to claim 1, characterized in that The total content of bacteriophage in the bacteriophage composition is 10 8 -10 10 PFU / mL.

3. The bacteriophage composition according to claim 1 or 2, characterized in that The mass ratio of the bacteriophage 4FS1, bacteriophage DS-BP2 and bacteriophage DS2 is 1:1:

1.

4. Use of the bacteriophage composition according to any one of claims 1 to 3 in the preparation of a product for preventing and treating Salmonella infection in equine abortion.

5. The use according to claim 4, characterized in that: In the phage composition, the infection multiplicity of phage 4FS1 is 0.001-0.1; the infection multiplicity of phage DS-BP2 is 0.01-0.1; and the infection multiplicity of phage DS2 is 0.001-0.

01.

6. A biological preparation for preventing and treating equine Salmonella abortus infection, comprising the bacteriophage composition according to any one of claims 1 to 3.

7. The biological agent according to claim 6, characterized in that The preparation is in any veterinary acceptable dosage form; preferably, the preparation is in a liquid dosage form.

8. Use of the biological preparation according to claim 6 or 7 in the preparation of a medicament for preventing and treating Salmonella abortus infection in horses.

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