Construction of an isogenic leukotoxin deletion mutant ofPasteurella haemolyticaserotype 1: characterization and virulence |
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| Affiliation: | 1. Laboratory of Veterinary Parasitology, Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Morioka 020-8550, Japan;2. National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Nishi 2-13 Inada-cho, Obihiro 080-8555, Japan;3. Department of Animal Medicine, Faculty of Veterinary Medicine, South Valley University, Qena 83523, Egypt;4. Transboundary Animal Diseases Research Center, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan;5. Apartment House Iris B101, 142-12 Shinogikurohata, Takizawa, Iwate 020-0735, Japan;6. Tyubu Area Center Veterinary Clinic, Iwate Agricultural Mutual Aid Association, 821 Shimoneko, Hanamaki, Iwate 025-0025, Japan;7. Field Center of Animal Science and Agriculture, Obihiro University of Agriculture and Veterinary Medicine, Japan;1. Environmental Microbial and Food Safety Laboratory, Agricultural Research Service, United States Department of Agriculture, Building 173, BARC-East, 10300 Baltimore Avenue, Beltsville, MD 20705, USA;2. CAPES Foundation, Ministry of Education of Brazil, Caixa Postal 250, 70040-020 Brasília, DF, Brazil;3. Universidade Estadual do Norte Fluminense Darcy Ribeiro, 28013-602, Campos dos Goytacazes, Rio de Janeiro, Brazil |
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| Abstract: | 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. |
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