China Animal Husbandry and Veterinary Medicine ›› 2022, Vol. 49 ›› Issue (10): 4085-4096.doi: 10.16431/j.cnki.1671-7236.2022.10.041

• Basic Veterinary Medicine • Previous Articles     Next Articles

Study on the Optimization of Modified Formula for Inhibiting Streptococcus equi subspecies equi and Its Bacteriostatic Effect in Vivo

ZHU Yixuan1, LIU Shipeng1, ZHANG Wei1, LI Jinrong1, PENG Fei2, LIN Na1, WANG Yuyan1, LIU Dandan1   

  1. 1. Institute of Animal Medicine, Xinjiang Agricultural University, Urumqi 830052, China;
    2. Manzhouli Customs Technology Center, Manzhouli 021400, China
  • Received:2022-03-08 Online:2022-10-05 Published:2022-09-30

Abstract: 【Objective】 The aim of this study was to screen the optimal Chinese herbal formula that could inhibit the main pathogen of strangles Streptococcus equi subspecies equi,and provide a new reference for the prevention and treatment of strangles.【Method】 27 kinds of herbs including Radix Paeoniae Rubra,Rhubarb and Radix Sophorae Sinensis etc.were used as materials in this experiment,antibacterial Chinese herbal medicines was preliminary screened by in vitro antibacterial test (Oxford cup method,minimum inhibitory concentration(MIC),minimum bactericidal concentration(MBC),combined drug susceptibility test) and L8(26) orthogonal test,and then the formula for inhibiting Streptococcus equi subspecies equi was composed.Secondly,the optimal ratio of basic formula was further screened by L18 (36) orthogonal test.Finally,under the premise of basic formula,according to the theory of compatibility theory of Chinese herbal formula,two tonifying drugs were added,the ratio of modified formula was screened by in vivo bacteriostasis test of strangles mice model,and the antibacterial effect of modified formula was verified in combination with formula protection rate and pathological changes of tissues and organs.【Result】 In the experiment,seven herbs (Fritillaria thunbergii,Radix Paeoniae Licorice root,Rhubarb,Nymphaea candida,Sophora root,Sophora flavescens) were selected,which were super sensitive and highly sensitive to Streptococcus equi subspecies equi,The MIC of Rhubarb,Nymphaea candida,Sophora root,Radix Paeoniae Rubra,Sophora flavescenswere 0.078,0.078,0.125,0.156,0.156 and 0.25 mg/mL,respectively.The MBC of Nymphaea candida,Radix Paeoniae,Sophora root,Licorice root,Rhubarb,Sophora flavescens,Fritillaria thunbergii were 0.078,0.125,0.125,0.156,0.156,0.156 and 0.25 g/mL,respectively.According to the MIC values of each single herb and the MIC values after pairwise combination,it was calculated that the combined herb sensitivity index of Fritillaria thunbergii and Nymphaea candida was>2,which was antagonistic,so Fritillaria thunbergii was deleted.Then the optimal ratio of the basic formula was obtained by two orthogonal tests as follows:RhubarbSophora flavescensSophora rootRadix Paeoniae RubraLicorice rootNymphaea candida= 4∶2∶2∶4∶1.Combined with the in vivo bacteriostasis test of modified formula,the protection rate was 87.5% when the compatibility concentration of Astragalus membranaceusAngelica sinensis = 1∶1 was 0.5 mg/mL,and Chinese herbal formula could repair inflammatory injury of lung induced by Streptococcus equi subspecies equi in mice.【Conclusion】 In conclusion,the study successfully screened out a new Chinese medicine formula with good antibacterial and tissue protection effects on Streptococcus equi subspecies equi.The ratio was RhubarbSophora flavescensSophora rootRadix Paeoniae Rubra:Licorice rootNymphaea candidaAstragalus-Angelica(1∶1)= 4∶2∶2∶4∶4∶1∶1.

Key words: strangle; Streptococcus equi subspecies equi; herbal formula; orthogonal test; bacteriostasis test

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