Isolation and Identification of Strain of Streptococcus equi Subspecies.equi from Donkey and Analysis of Its Biological Characteristics
Toexplore the pathogenic bacteria and related biological characteristics of donkey strangles in a donkey farm in Kashgar,Xinjiang,bacteria from collected samples using sheep fresh blood culture medium were isolated and purified.The isolated bacteria were identified through Gram staining,mi-croscopy,and PCR amplification.MEGA 7.0 biological software was used to draw the genetic evolu-tion tree of isolated bacteria,and the growth curve of isolated bacteria was drawn and their biological characteristics were analyzed through conducting in vivo pathogenicity tests,virulence gene detection tests,and drug sensitivity tests.The results the isolation of a strain of streptococci with β-hemolytic properties and a positive Gram stain.The sequencing results were compared with GenBank's Blast and showed a high homology of 99.01％with the registered Streptococcus equi subspecies.equi.The genetic evolution tree analysis indicated that the genetic distance between the isolates of Streptococcus equi subspecies.equi from the donkey and the isolates of Streptococcus equi subspecies.equi from Xinjiang HTP133(MT815602.1)was similar,the isolates were named LXY019 strain.The growth curve showed that the isolated bacteria reached a plateau period after 8 hours and began to decline af-ter 18 hours.Pathogenicity results indicated that the LD50 of the isolated strain in mice was 1.58 X 107 CFU/mL.Virulence gene identification indicated that the isolated strain carried fneB and seM.The final drug sensitivity test results showed that the isolated bacteria were sensitive to β-Lactam an-tibiotics and macrolide antibiotics were highly sensitive,while aminoglycoside antibiotics were relative-ly insensitive.These findings showed that the Streptococcus equi subspecies isolated and purified from donkeys exhibits obvious pathogenicity in mice,and β-lactam antibiotics and macrolide antibiotics are recommended for clinical treatment.The results provide a reference for the prevention and treatment of donkey strangles caused by this pathogen.
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