Identification Of Pasteurella Multocidaserotype And Pathogenesis Investigation Of Capsule Serotypef Strain Isolated From Pigs In Hunan Province

A total of 124 Pasteurella multocida strains isolated from in this labby using blood agar and PCR method from 421 lungsand 180 tonsils of slaughtered pigs,147 lungs of pneumonic pigs and 53 nasal swabs of pigsin Hunan Province.64 belonged to A: L3,16 belonged to A: L6,38 belonged to D: L6,4 belonged to F: L3,1 belonged to L3 but failed to capsular type and 1 isolated was untypeable.PCR was used for detecting 23 virulence-associated genes harboured in those isolates,the average number of the virulence-associated genes was 17.0.Of the 49 strains carried 18 virulence genes,33 were A: L3,16 were A: L6,1 strain could not be identified serotypeand had at least 14 virulence genes.The detection rates of virulence genes were 98% ~ 100% in 124 strains,respectively,these virulence genes were ptfA,fimA,hsf-2,sodA,sodC,ompA,ompH,oma87,plpB,exbB,exbD,tonB,Fur and nanH,all strains did not contain tbpA gene.The distribution of 8 virulence genes in different serotypes was different,which were hsf-1,pfhA,tadD,toxA,pmHAS,hgbA,hgbB and nanB respectively.Mice were used for pathogenesis investigation,after culture medium of the 4 strains were diluted,mice were challenged by intraperitoneal injection at dose 4 CFU/mouse,5 CFU/mouse,11 CFU/mouse and 17 CFU/mouse,respectively.All of mice died after 60 h and high pathogenicities of these 4 strains were presented.The alveolar hyperaemia,splenic lymphocyte apoptosis of mice were revealed in pathological sections.Among antimicrobial susceptibility test,these 4 strains had high sensitivity to enrofloxacin,florfenicol,cefradine,cefazolin,ceftriaxone,ciprofloxacin and cefotaxime,showed moderate sensitivity todoxycycline,penicillin,erythromycin,lincomycin,amoxicillin and ofloxacin,low sensitivity to amikacin,streptomycin,kanamycin and gentamicin.It's first time to isolate P.multocidaserotypes F in Hunan province and make a more detailed study on the biological characteristics.This study contributed to supplement the reference materials of domestic P.multocida prevention and epidemiological surveillance.