Isolation,identification and biological characteristics of Mannheimia haemolytica in respiratory tract of lambs in Xinjiang
To investigate the biological characteristics of Mannheimia haemolytica(Mh)in the re-spiratory tract of lambs under six months of age in Xinjiang,two hundred and ninety nasal swabs were collected from lambs in eight large-scale sheep farms across five regions of Xinjiang.The na-sal swabs were subjected to conventional bacterial isolation and identification,as well as PCR iden-tification methods to isolate and identify bacteria.The isolated strains were then tested for capsular serotype,MLST typing,virulence genes,drug sensitivity,and drug resistance genes.The results showed that out of the two hundred and ninety nasal swabs,a total of fourteen strains of Mh(Mh42-Mh56)were isolated;among the capsular serotypes,nine strains were untyped,three strains were A2 type,one strain was A1 type,and one strain was A6 type;MLST typing revealed five strains of ST16,four strains of ST28,one strain of ST46,and four strains of undetermined type.In infected mice,mortality began at 10 h post infection,with a 40％survival rate at 96 h post infection.The lungs of the deceased mice showed congestion,swelling,hemorrhage,and fleshy ap-pearance.All 14 strains of Mh carried dnaN,gapA,fbpA,gs60,and lktC genes,with a carrying rate of 42.85％for sodA.None of the strains carried plpB,tonB,pt fA,and fimA genes.Mh42 showed resistance to doxycycline,midecamycin,and florfenicol,while Mh54 was resistant to enro-floxacin and ciprofloxacin.However,the remaining strains did not exhibit resistance to any of the twenty-one drugs tested.Additionally,no drug resistance gene was detected in fourteen strains of Mh.This study provides valuable insights into the epidemiology,clinical prevention,and treatment of Mh in the respiratory tract of lambs in Xinjiang.
lambrespiratory tractMannheimia haemolyticaisolation and identificationvirulence genesdrug resistance
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