Salmonella phage nct1 and application thereof

Abstract

The application discloses a Salmonella phage nct1, and the Salmonella phage nct1 (Salmonella phage nct1) has a preservation number of CCTCC NO: M 20221037. The Salmonella phage nct1 has small toxic and side effects, high safety, a relatively wide temperature and acid-base tolerance range, and good killing and prevention and control effects on environments, foods and the like contaminated by Salmonella and pathogenic Escherichia coli.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bacteriophage technology, in particular to a Salmonella bacteriophage nct1 and its application. BACKGROUND

[0002] Salmonella is one of the most common pathogenic bacteria of animal food-borne diseases, and is a global public health problem. In addition to causing typhoid fever and paratyphoid fever, Salmonella is also the main pathogen of common and frequently-occurring diseases such as bacterial food poisoning and diarrhea, and can cause widespread epidemics in poultry and livestock, affecting the development of industrial and agricultural production and foreign trade. Among Salmonella, the most pathogenic is Salmonella cholerae, followed by Salmonella typhimurium and Salmonella enteritidis.

[0003] Bacteriophage (bacteriophage, phage) is a general term for viruses that infect bacteria, fungi, algae, actinomycetes or spirochetes and other microorganisms. Because some can cause lysis of host bacteria, they are called bacteriophages. Bacteriophage is a kind of virus, which is special in that it only uses bacteria as host, just like other viruses. Bacteriophage is only a mass of genetic material wrapped in a protein shell, and most bacteriophages also have "tails" to inject genetic material into the host.

[0004] Chinese application CN112680423A discloses a wide-spectrum strong-lytic Escherichia coli bacteriophage capable of lysing four kinds of bacteria simultaneously. In addition to having good lytic effect on Escherichia coli, the bacteriophage can also lyse Shigella, Salmonella and Enterobacter cloacae, and can be produced on a large scale, showing the prospect of bacteriophage in practical application. Chinese application CN108359644A discloses a long-tailed wide-host-spectrum Salmonella gallinarum strong-lytic bacteriophage SP4. The bacteriophage has strong lytic effect on Salmonella, and can also reduce the mortality rate of infected chicklings. The preparation can be used alone or in a cocktail, providing a safe, non-toxic and non-residual bacteriophage product source for the treatment of chicken, duck, mink, food and pig source Salmonella infection, and has a wide application prospect in the breeding industry and food industry.

[0005] Salmonella typhimurium is one of the most common and strongest pathogenic bacteria of animal food-borne diseases, which has brought huge economic losses to the livestock industry. Therefore, it is necessary to find a new Salmonella bacteriophage isolate that can kill multiple bacteria simultaneously, has high stability, good safety and high titer. SUMMARY

[0006] The present application is directed to the above technical problems, providing a broad-spectrum multivalent Salmonella phage capable of lysing 3 strains of Salmonella enteritidis, 15 strains of Escherichia coli and 10 strains of Klebsiella pneumoniae, aiming to provide a new prevention and control means for environmental and food contamination caused by Salmonella and Escherichia coli.

[0007] To achieve the above-mentioned purpose, the technical scheme provided by the present application is as follows:

[0008] A strain of Salmonella phage nct1, named Salmonella phage nct1 (Salmonella phage nct1), with the preservation number CCTCC NO: M 20221037, preserved on July 5, 2022, and preserved at Wuhan University China Typical Culture Collection Center, Wuchang District, Wuhan City, Hubei Province.

[0009] The application of the above-mentioned Salmonella phage nct1 in the preparation of drugs for preventing and treating diseases caused by Salmonella infection.

[0010] The application of the above-mentioned Salmonella phage nct1 in the preparation of drugs for preventing and treating diseases caused by Escherichia coli infection.

[0011] The application of the above-mentioned Salmonella phage nct1 in the preparation of drugs for preventing and treating diseases caused by Klebsiella pneumoniae infection. A phage composition comprising the above-mentioned Salmonella phage nct1.

[0012] A phage pharmaceutical preparation, wherein the effective component comprises the above-mentioned Salmonella phage nct1 or the above-mentioned phage composition.

[0013] The phage pharmaceutical preparation further comprises a pharmaceutically acceptable carrier, and the dosage form is solution, powder, gel, granules or lyophilized agent.

[0014] A water body disinfectant, wherein the effective component comprises the above-mentioned Salmonella phage nct1 (Salmonella phage nct1) or the above-mentioned phage composition; and wherein the disinfectant further comprises other active ingredients for inhibiting or eliminating viruses and bacteria in the environment.

[0015] The disinfectant can be used to disinfect Salmonella in the breeding environment, feeding appliances and feed by spraying or soaking.

[0016] The Salmonella phage nct1 has good killing effect, can prolong the storage time of food, has high stability, good safety, is easy to be made into a preparation, and can be widely used in the fields of food, environment and feed disinfection of Salmonella and Escherichia coli.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The salmonella phage nct1 has small toxic side effects, high safety, and a relatively wide temperature and acid-base tolerance range, and has a good killing and prevention effect on environments, foods and the like contaminated by salmonella and pathogenic E. coli.

[0019] Deposit Information

[0020] The salmonella phage nct1 was preserved in the China Center for Type Culture Collection (CCTCC) on July 5, 2022, and the preservation number is CCTCC NO: M 20221037. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a plaque picture of the salmonella phage nct1 of the application.

[0022] Figure 2 is a transmission electron microscope picture of the salmonella phage nct1 of the application.

[0023] Figure 3 is a graph of the optimal infection multiple of the salmonella phage nct1 of the application.

[0024] Figure 4 is a one-step growth curve graph of the salmonella phage nct1 of the application.

[0025] Figure 5 is a schematic diagram of the influence of temperature on the activity of the salmonella phage nct1 of the application.

[0026] Figure 6 is a schematic diagram of the influence of pH on the activity of the salmonella phage nct1 of the application.

[0027] Figure 7 is a schematic diagram of the sterilization of the salmonella phage nct1 of the application in a liquid medium.

[0028] Figure 8 is a schematic diagram of the sterilization of the salmonella phage nct1 of the application in chicken ham sausages. DETAILED DESCRIPTION

[0029] The specific embodiments will be described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the application is not limited by the specific embodiments. The raw materials and reagents used in the examples are commercially available unless otherwise specified.

[0030] The host bacteria used in the experiment are standard strain CVCC3384, which is purchased from the China Center for Type Culture Collection.

[0031] LB (Luria broth) liquid medium (1 L): Tryptone 10 g, Yeast extract 5 g, NaCl 10 g, add ddH2O to 1 L, adjust pH to 7.0, autoclave at 121 °C for 20 min.

[0032] 0.6% LB semi-solid medium (1 L): Tryptone 10 g, Yeast extract 5 g, NaCl 10 g, Agar powder 6 g, add ddH2O to 1 L, adjust pH to 7.0, autoclave at 121 °C for 20 min.

[0033] 1.2% LB solid medium (1 L): Tryptone 10 g, Yeast extract 5 g, NaCl 10 g, Agar powder 12 g, add ddH2O to 1 L, adjust pH to 7.0, autoclave at 121 °C for 20 min, cool to 50 °C, pour plates, cool to solidify, invert and store.

[0034] SS solid medium (1 L): SS agar powder 5.65 g, add ddH2O to 1 L, adjust pH to 7.0, autoclave at 121 °C for 20 min.

[0035] SM buffer (1 L): Weigh 6.055 g Tris-HCI (pH 7.5) to 100 ml, add 5.800 g NaCl, 2.000 g MgSO4, then add ddH2O to 1 L.

[0036] PBS buffer (1 L): 8 g NaCl, 0.2 g KCl, 1.44 g Na2HPO4, 0.24 g HPO4, add ddH2O to 1 L, adjust pH to 7.4, autoclave at 121 °C for 20 min.

[0037] DNase I, RNase A, PEG8000, phosphotungstic acid (PTA, 2% w / v) were commercially available.

[0038] Example 1

[0039] Isolation of Salmonella phage nct1

[0040] The host bacteria CVCC3384 purchased from China Veterinary Microbiological Culture Collection Center was streaked on SS solid medium and incubated overnight, then a single colony was inoculated in 5 mL LB (Luria broth) liquid medium, which was incubated at 37 °C for 8 h as host bacteria culture, ready for use.

[0041] The sample was taken from the sewage in the septic tank of a cattle farm in Chongzuo, Guangxi. The sample was centrifuged at 12000 rpm for 10 min at 4°C, and the supernatant was centrifuged again for 3 times. The final supernatant was filtered through 0.45 μm and 0.22 μm filter membranes. 5 mL of the filtrate was taken, 0.1 mL of the prepared host bacteria culture was added, 5 mL of 2xLB liquid medium was added, and the mixture was incubated at 37°C for 14-16 h. The next day, the culture obtained after incubation for 14-16 h was centrifuged at 12000 rpm for 10 min at 4°C, and the supernatant was filtered through a 0.22 μm filter membrane to remove bacteria, thereby obtaining a phage-containing stock solution, i.e., a phage suspension.

[0042] The 1.2% LB solid medium was divided into two regions, 0.1 mL of the prepared host bacteria culture and 3 mL of 0.6% LB semi-solid medium were mixed uniformly and then spread on the 1.2% LB solid medium. After the medium was dried, 10 μL of the above phage suspension was dropped on one of the regions, and the medium was incubated in a 37°C incubator. The formation of plaques in the region where the phage suspension was dropped was observed. If plaques were formed, it indicated that the phage existed.

[0043] Another 0.1 mL of the above phage suspension was serially diluted by 10 times, and 0.1 mL of each of the dilutions was added to 0.1 mL of the prepared host bacteria culture, and the mixture was incubated at 37°C for 14-16 h. The next day, the culture was centrifuged at 12000 rpm for 10 min at 4°C, and the supernatant was filtered through a 0.22 μm filter membrane to remove bacteria, thereby obtaining a phage-containing stock solution, i.e., a phage suspension. -2 , 10 -4 , 10 -6 mL of each of the dilutions was added to 0.1 mL of the prepared host bacteria culture, and the mixture was incubated at 37°C for 14-16 h. The next day, the culture was centrifuged at 12000 rpm for 10 min at 4°C, and the supernatant was filtered through a 0.22 μm filter membrane to remove bacteria, thereby obtaining a phage-containing stock solution, i.e., a phage suspension.

[0044] The prepared phage was detected by double-layer plate method, and the results are shown in Table 1. Figure 1 The phage formed transparent plaques in the agar medium, and the plaques were surrounded by no halo and had clear and regular edges with a diameter of about 0.2 mm, which was a typical lytic phage.

[0045] Example 2

[0046] Amplification and purification of Salmonella phage nct1

[0047] Take the 0.1 mL of the phage stored at 4°C and the 0.1 mL of the host bacteria culture prepared in Example 1 and mix them in a test tube for 15 min. Add 10 mL of LB liquid medium and incubate at 37°C for 6 h. Centrifuge at 12,000 rpm for 20 min at 4°C. Take the supernatant and filter it through a 0.22 μm filter. The filtrate is the phage lysate.

[0048] PEG purification: Add DNase I and RNase A to the phage lysate to a final concentration of 1 μg / mL and incubate at 37°C for 30 min. Add NaCl to a final concentration of 1 M and incubate in an ice bath for 1 h. Centrifuge at 12,000 rpm for 10 min at 4°C. Add PEG 8000 to a final concentration of 10% and incubate at 4°C overnight. Centrifuge at 12,000 rpm for 10 min at 4°C. Discard the supernatant and invert the test tube for 5 min to remove excess water. Resuspend the remaining solid material in SM buffer. Add an equal volume of chloroform and gently shake for 30 s. Separate the organic and hydrophilic phases by centrifugation at 5,000 rpm for 15 min at 4°C. Recover the hydrophilic phase containing the phage particles to obtain the purified phage suspension.

[0049] Double-layer agar plate method for detecting phage titer: Dilute the purified phage suspension described above by a factor of 10. Mix 0.1 mL of each dilution with 0.1 mL of the host bacteria culture prepared in Example 1 and spread on a double-layer agar plate. Incubate at 37°C for 6-10 h. Count the plaques on each plate. Select the plates with 30-300 plaques. Calculate the initial concentration of the phage based on the dilution factor to obtain the phage titer. The phage titer (PFU / mL) = dilution factor x number of plaques x 10. The phage titer is 6.0 x 10 9 PFU / mL.

[0050] Example 3

[0051] Transmission electron microscopy observation of Salmonella phage nct1

[0052] Example 2: Electron microscopy observation of the purified phage suspension: Drop the purified phage suspension of Example 2 on a copper sheet and allow it to settle for 5-10 min. Absorb the excess liquid with filter paper. Drop a drop of 2% phosphotungstic acid (PTA, 2% w / v) for staining. Dry at room temperature and observe using a transmission electron microscope. The observation results are shown in Figure 2. Figure 2As shown, the phage has a head of a regular icosahedron, the head diameter is about 51.0 nm, and the tail is about 125.0 nm long. According to the International Committee on Taxonomy of Viruses (ICTV) Eighth Report on the Taxonomy of Viruses published in 2015, the phage belongs to the Siphoviridae family and is named nct1.

[0053] Example 4

[0054] Host spectrum analysis of Salmonella phage nct1

[0055] The phage stock reserved in Example 1 at 4°C was adjusted to 10 9 PFU / mL. The host spectrum of the phage was analyzed using 60 strains of bacteria isolated from different sources, according to the following procedure: 0.1 mL of the overnight culture of each of the 60 strains of bacteria was added to 3 mL of 0.6% LB semi-solid medium at about 45°C, and evenly spread on a previously prepared solid 1.2% LB solid medium. Then, each plate was evenly divided into two regions, 10 μL of the phage with a titer adjusted to 10 9 PFU / mL was added to the surface of one region, and physiological saline was added to the surface of the other region as a control. After the droplets dried, the plates were inverted and incubated at 37°C for 12 h. The results were observed, and if plaques were produced, it was recorded as “+”, otherwise as “-”. The results are shown in Table 1: In addition to being able to lyse the host bacteria CVCC3384, the Salmonella phage nct1 can also lyse 2 other strains of Salmonella, 15 strains of Escherichia coli from different sources, and 10 strains of Klebsiella pneumoniae.

[0056] Table 1. Host spectrum information of Salmonella phage nct1

[0057] No. Strain name Strain species Strain source Source Lysis profile 1 CVCC1806 Salmonella China Veterinary Culture Collection + 2 Avian JSSP1014 Salmonella - - 3 China Veterinary Culture Collection FJSP0923 - + 4 Salmonella China Veterinary Culture Collection - - 5 ATCC25922 Escherichia coli China Veterinary Culture - - 6 Collection CVCC4050 Escherichia coli China Veterinary Culture - 7 Collection GXEC-22 Escherichia coli Nanning, Guangxi + 8 Avian GXEC-23 Escherichia coli Nanning, Guangxi - 9 Avian GXEC-32 Escherichia coli Nanning, Guangxi - 10 Avian GXEC-33 Escherichia coli Nanning, Guangxi + 11 Avian GXEC-34 Escherichia coli Nanning, Guangxi - 12 Avian GXEC-35 Escherichia coli Nanning, Guangxi - 13 Avian GXEC-36 Escherichia coli Nanning, Guangxi + 14 Avian GXEC-37 Escherichia coli Nanning, Guangxi - 15 Avian GXEC-38 Escherichia coli Nanning, Guangxi - 16 Avian GXEC-39 Escherichia coli Nanning, Guangxi - 17 Avian GXEC-40 Escherichia coli Nanning, Guangxi + 18 Avian GXEC-41 Escherichia coli Nanning, Guangxi + 19 Avian GXEC-42 Escherichia coli Nanning, Guangxi - 20 Avian GXEC-43 Escherichia coli Nanning, Guangxi + 21 Avian GXEC-50 Escherichia coli Nanning, Guangxi - 22 Avian GXEC-51 Escherichia coli Nanning, Guangxi - 23 Avian GXEC-52 Escherichia coli Nanning, Guangxi - 24 Avian GXEC-53 Escherichia coli Nanning, Guangxi - 25 Avian GXEC-54 Escherichia coli Nanning, Guangxi - 26 Avian GXEC-55 Escherichia coli Nanning, Guangxi + 27 Avian GXEC-56 Escherichia coli Nanning, Guangxi + 28 Avian GXEC-57 Escherichia coli Nanning, Guangxi - 29 Avian GXEC-58 Escherichia coli Nanning, Guangxi + 30 Avian GXEC-59 Escherichia coli Nanning, Guangxi - 31 Avian GXEC-60 Escherichia coli Nanning, Guangxi + 32 Avian SXEC-1 Escherichia coli Zigong, Sichuan - 33 Avian SXEC-2 Escherichia coli Zigong, Sichuan - 34 Avian SXEC-3 Escherichia coli Zigong, Sichuan - 35 Avian GDEC-32 Escherichia coli Foshan, Guangdong + 36 Pig GDEC-33 Escherichia coli Foshan, Guangdong + 37 Pig GDEC-34 Escherichia coli Foshan, Guangdong - 38 Pig GDEC-67 Escherichia coli Foshan, Guangdong - 39 Pig GDEC-68 Escherichia coli Foshan, Guangdong + 40 Pig GDEC-69 Escherichia coli Foshan, Guangdong + 41 Pig GDEC-70 Escherichia coli Foshan, Guangdong - 42 Pig FJEC-4 Escherichia coli Fujian + 43 Human FJEC-5 Escherichia coli Fujian - 44 Human FJEC-6 Escherichia coli Fujian - 45 Human GXKP-6 Klebsiella pneumoniae Nanning, Guangxi + 46 Human GXKP-20 Klebsiella pneumoniae Nanning, Guangxi + 47 Human GXKP-49 Klebsiella pneumoniae Nanning, Guangxi - 48 Human GXKP-54 Klebsiella pneumoniae Nanning, Guangxi - 49 Human GXKP-L1 Klebsiella pneumoniae Nanning, Guangxi - 50 Human GXKP-L3 Klebsiella pneumoniae Nanning, Guangxi + 51 Human GXKP-L15 Klebsiella pneumoniae Nanning, Guangxi - 52 Human GXKP-L22 Klebsiella pneumoniae Nanning, Guangxi + 53 Human GXKP-L28 Klebsiella pneumoniae Nanning, Guangxi + 54 Human GXKP-L30 Klebsiella pneumoniae Nanning, Guangxi + 55 Human GXKP-L31 Klebsiella pneumoniae Nanning, Guangxi Human GXKP-L34 Klebsiella pneumoniae Nanning, Guangxi Human + 56 GXKP-L40 klebsiella pneumoniae guangxi nanning human + 57 GXKP-L45 klebsiella pneumoniae guangxi nanning human + 58 GXKP-L48 klebsiella pneumoniae guangxi nanning human - 59 GXKP-L59 klebsiella pneumoniae guangxi nanning human + 60 GXKP-RS3 klebsiella pneumoniae guangxi nanning human -

[0058] Example 5

[0059] Determination of the optimal multiplicity of infection of Salmonella phage nct1 (the multiplicity of infection is the ratio of the number of phages to the number of host bacteria at the initial stage of infection)

[0060] The host bacteria culture stock reserved in Example 1 was adjusted to a concentration of 1.0 x 10 9 CFU / mL. The phage stock reserved in Example 1 and the host bacteria culture stock reserved in Example 1 were added in proportions of 100, 10, 1, 0.1, and 0.01, respectively, according to the multiplicity of infection. LB (Luria broth) liquid medium was added to make the total volume of the culture system the same. The culture was incubated at 37°C for 5 h, centrifuged at 12,000 rpm for 10 min, and the supernatant was collected and diluted to an appropriate concentration. The titer was determined by the double-layer plate method, and the results are shown in Table 2. figure 3The optimal multiplicity of infection of the Salmonella phage nctl is 100.

[0061] Example 6

[0062] Determination of the one-step growth curve of the Salmonella phage nctl

[0063] The host bacteria culture prepared in Example 1 was mixed with excess phage prepared in Example 1 (MOI > 10, to ensure that all bacteria were adsorbed with phage), and then incubated at 37°C for 15 min, followed by centrifugation at 12000 rpm for 1 min. The supernatant (unadsorbed phage) was discarded, and the precipitate (mutually adsorbed bacteria and phage particles) was washed once with LB liquid medium. The precipitate was resuspended in 10 mL of preheated LB liquid medium, and then quickly placed in a 37°C shaking incubator. At 10-min intervals, 120 μL of the culture was taken from 0 min, and then centrifuged at 10000 rpm for 2 min at 4°C to remove the bacteria. The supernatant was diluted to an appropriate concentration (an appropriate concentration is a concentration that forms 30-300 plaques on a plate), and then the phage titer was determined by double-layer plate method. The determination was performed for 120 min, and a total of 12 samples were taken. The sampling time was used as the horizontal coordinate, and the logarithm of the phage titer was used as the vertical coordinate. The one-step growth curve was plotted to obtain the latent period, burst period, and burst size of the phage. The one-step growth curve results are shown in Figure 1. figure 4 As shown in Figure 1, the latent period of the phage for infecting host bacteria was 50 min, the burst period was 20 min, the burst size was 110 PFU / CFU, and the phage entered a stable phase after 70 min, and maintained at a relatively high concentration.

[0064] Example 7

[0065] Temperature and pH tolerance experiment of the Salmonella phage nctl

[0066] Ten sterile EP tubes were taken, and 0.5 mL of the phage prepared in Example 1 was added to each tube. The tubes were then subjected to 30 min and 60 min of action at 4°C, 25°C, 37°C, 50°C, 60°C, 70°C, and 80°C, respectively. After the action time, the tubes were immediately placed in a water bath for cooling, and then the titer of the phage was determined. The detection results are shown in Figure 2. figure 5 As shown in Figure 2, the phage can tolerate high temperature of 60°C, and the titer of the phage is basically stable within 60 min. When the temperature is greater than 60°C, the titer of the phage decreases significantly with time, and even becomes inactivated. When the temperature reaches 80°C, the phage is completely inactivated.

[0067] Eleven portions of 0.1 mL of the phage prepared in Example 1 were taken and placed in SM buffer (0.9 mL) with pH values of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 13, respectively. The tubes were then subjected to 1-2 h of action at 37°C, and then the titer of the phage after the reaction was determined by double-layer plate method. The detection results are shown in Figure 3. figure 6As shown: the phage titer changes little in the environment with pH value of 3-11, and the activity is basically unchanged; when the environmental pH > 11 or pH < 3, the phage titer is 0, and the phage is in an inactive state, i.e. the optimum pH of the phage is 3-11.

[0068] Example 8

[0069] Bactericidal effect of Salmonella phage nct1 in liquid medium

[0070] Take the host bacteria culture (CVCC3384) prepared in Example 1, dilute to 1x10 6 CFU / ml, take 4 sterile test tubes, add 3ml LB liquid medium to the control group, add 1.5ml of the host bacteria culture and 1.5mL of the phage prepared in Example 1 with different concentrations according to MOI=100 (optimal multiplicity of infection) and MOI=10 to the experimental group respectively, and place in a 37°C shaking incubator (180rpm) for continuous shaking, 3 repeats for each group; measure the OD450nm of the co-culture of host bacteria and phage every hour by spectrophotometer, and the results of the bactericidal experiment of the phage are as shown in figure 7 The positive control group, i.e. the culture medium only with host bacteria without phage, has a significant increase in OD450nm within 11h, and maintains at a relatively high level. When MOI=100, the viable count of Salmonella starts to increase at 5h, and maintains at a stable level after 11h of phage treatment. When MOI=10, the viable count of Salmonella starts to increase at 5h, and then slightly decreases after 12h of treatment. There is no significant difference between the effect of MOI=100 and the effect of MOI=10. In summary, the Salmonella phage nct1 has good application prospect in the prevention and control of Salmonella contamination.

[0071] Example 9

[0072] Bactericidal effect experiment of Salmonella phage nct1 in ham sausages

[0073] Take the commercially available chicken ham sausages, dilute the host bacteria culture (CVCC3384) prepared in Example 1 to 4x10 3 CFU / ml, take 25μL to inoculate on the ham sausage slices. Add 25μL SM buffer to the control group, and add 25μL of the host bacteria culture and 50μL of the phage prepared in Example 1 with different concentrations according to MOI=100 (optimal multiplicity of infection) and MOI=10 to the experimental group respectively, and incubate at 4°C and 28°C for 48h respectively. At 2h, 4h, 6h, 24h and 48h of incubation, take samples for grinding, dilute with PBS buffer, and determine the bacterial number by plate counting method. 3 repeats for each group. The results of the bactericidal experiment of the phage in the ham sausages are as shown in figure 8As shown, the positive control group, i.e. the ham sausage only added with host bacteria without added phage, the number of bacteria increased significantly within 48h with the extension of incubation time, and maintained at a higher level. When MOI = 100, the temperature was 4℃, the number of live host bacteria in the phage treatment group was significantly reduced at 6h, 24h, 48h. When MOI = 10, the temperature was 4℃, the number of live host bacteria was significantly reduced at 6h, 24h, 48h. At 4℃, the phage treatment group with MOI = 100 showed stronger antibacterial effect than the phage treatment group with MOI = 10 figure 8 A). At 28℃, when MOI was 100 and 10, the number of live host bacteria in the phage treatment group was significantly reduced after 4h, 24h, 48h of culture figure 8 B). From the above, it can be seen that the Salmonella phage nct1 of the present application has great potential in controlling the pollution of common foodborne pathogenic bacteria Salmonella in ham sausage.

[0074] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms described. Many modifications and variations are possible in light of the above teachings without departing from the spirit or essential characteristics of the present application. The exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application and to allow others skilled in the art to understand the application for various exemplary embodiments with various modifications being applicable. The scope of the application is intended to be defined by the claims and their equivalents.

Claims

1. A bacteriophage of Salmonella nctl, characterized in that, The Salmonella phage nct1 has a preservation number of CCTCC NO: M 20221037.

2. Use of the Salmonella phage nct1 of claim 1 in the preparation of a medicament for treating diseases caused by Salmonella infection.

3. Use of the Salmonella phage nct1 of claim 1 in the preparation of a medicament for treating diseases caused by Escherichia coli infection.

4. Use of the Salmonella phage nct1 of claim 1 in the preparation of a medicament for treating diseases caused by Klebsiella pneumoniae infection.

5. A bacteriophage composition comprising the Salmonella phage nct1 of claim 1.

6. A bacteriophage pharmaceutical preparation, which comprises the Salmonella phage nct1 of claim 1 or the bacteriophage composition of claim 5 as an effective component.

7. The bacteriophage pharmaceutical preparation of claim 6, wherein: The bacteriophage pharmaceutical preparation further comprises a pharmaceutically acceptable carrier, and the dosage form is a solution, a powder, a gel, a granule or a lyophilized agent.

8. A water body disinfectant, which comprises the Salmonella phage nct1 of claim 1 or the bacteriophage composition of claim 5 as an effective component; and further comprises other active components for inhibiting or eliminating viruses and bacteria in the environment.

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