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Type: Journal article
Title: Inactivation of two haemolytic toxin genes in Aeromonas hydrophila attenuates virulence in a suckling mouse model
Author: Wong, C.
Heuzenroeder, M.
Flower, R.
Citation: Microbiology, 1998; 144(2):291-298
Publisher: Microbiology Society
Issue Date: 1998
ISSN: 1350-0872
Abstract: The contribution of two unrelated Aeromonas hydrophila beta-haemolytic toxins to virulence was assessed in a suckling mouse model. The first haemolysin gene, isolated from an A. hydrophila A6 cosmid bank, encoded a potential gene product of 621 amino acids and a predicted molecular size of 69.0 kDa. The inferred amino acid sequence showed 89% identity to the AHH1 haemolysin of A. hydrophila ATCC 7966, and 51% identity to the HlyA haemolysin of Vibrio cholerae EI Tor strain O17. The second haemolysin gene (designated aerA), which encodes aerolysin, a pore-forming toxin, was partially cloned by PCR for the purpose of mutant construction. This PCR product was a 1040 bp fragment from the C-terminal region of aerA. It is proposed that the 69.0 kDa V. cholerae-HlyA-like haemolysin gene be termed hlyA to contrast with the aerA terminology for the aerolysin. A suicide vector was used to inactivate both the hlyA and aerA genes in A. hydrophila A6. When assessed in the suckling mouse model, only the hlyA aerA double mutant showed a statistically significant reduction in virulence--a 20-fold change in LD50 (Scheffe test, P < 0.05). Cytotoxicity to buffalo green monkey kidney cell monolayers and haemolysis on horse blood agar were eliminated only in the hlyA aerA double mutants. This is the first report of cloning and mutagenesis of two unrelated haemolytic toxin genes in the same strain of a mesophilic aeromonad. For A. hydrophila, a two-toxin model provides a more complete explanation of virulence.
Keywords: Cells, Cultured
Aeromonas hydrophila
Gram-Negative Bacterial Infections
Bacterial Proteins
DNA, Bacterial
Bacterial Toxins
Biological Assay
Cloning, Molecular
Mutagenesis, Insertional
Polymerase Chain Reaction
Sequence Analysis, DNA
Gene Expression
Polymorphism, Restriction Fragment Length
Molecular Sequence Data
Pore Forming Cytotoxic Proteins
Hemolysin Proteins
DOI: 10.1099/00221287-144-2-291
Appears in Collections:Aurora harvest 2
Microbiology and Immunology publications

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