| Autor: |
Tatum, Fred M, Briggs, Robert E, Sreevatsan, Srinand S, Zehr, Emile S, Ling Hsuan, Shih, Whiteley, Laurence O, Ames, Trevor R, Maheswaran, Samuel K |
| Zdroj: |
Microbial Pathogenesis; January 1998, Vol. 24 Issue: 1 p37-46, 10p |
| Abstrakt: |
Allelic replacement was used to generate two isogeniclktAdeletion mutants ofPasteurella haemolyticaserotype 1 that were incapable of synthesizing leukotoxin (Lkt). Southern blot data confirmed thatlktAsequences were absent in the twoP. haemolyticadeletion mutants. Culture supernatants and whole cell lysates from the wild typeP. haemolytica, D153 parent strain, but not thelktAdeletion mutants, contained immunoreactive and bioactive leukotoxic protein. In addition, only the parent strain was haemolytic when grown on bovine and sheep blood agar plates. Virulence of thelktAdeletion mutant,lktA77, was compared with the parent in an experimentally infected calf model of pneumonic pasteurellosis. Results revealed significant reduction in virulence in thelktAmutant as measured by clinical and lung lesion scores. Notable differences in histological changes such as markedly reduced necrosis and lack of leukocyte degeneration occurred in calves infected with thelktAmutant in comparison with those infected with the parent wild-type strain. Thus, it appears that leukotoxin plays a important role in the pathogenesis of lung injury in bovine pneumonic pasteurellosis. |
| Databáze: |
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