The Enterococcus faecalis SL22 strain was previously isolated from a milk cow with mastitis.In the present study,the strain SL22 used as the host bacteria for bacteriophage isolation from clinical mastitis milk samples.The isolated bacteriophage was characterized for its biological characteristics,virulence genes,drug resistance genes and possible use in mouse treatment.As a result,one bacterion age was isolated.The plaque formed by this bacteriophage was like a needle tip.Examination under the electron microscope found that the bacteriophage had no tail and its head formed a symmetrical polyhedron with a diameter of about 66 nm.It was named vB-EcoT_PSL22(PSL22).The bacteriophage PSL22 was lytic to its host bacteria only with MOI at 0.1 and pyrolysis quantity of about 52 PFU/cell.The lytic activity was stable at pH4.0-12.0 and tolerized a high temperature of about 60℃.In the mouse treatment experiment,the cure rate was 33.33％(2/6).The bacteriophage PSL22 possessed dsDNA,2 drug resistance genes(Acc and aac(3)-Ⅳ)and 4 virulence genes(gelE,cylA,ace and efaA).The results from this experiment provided a reference for the study of the phage diversity in dairy breasts with clinical mastitis and the micro-ecosystem in dairy breasts.
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