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Appl Environ Microbiol. 2017 Oct 13. pii: AEM.01814-17. doi: 10.1128/AEM.01814-17. [Epub ahead of print]

Conjugation-mediated horizontal gene transfer of Clostridium perfringens plasmids in the chicken gastrointestinal tract results in the formation of new virulent strains.

Author information

1
Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
2
CSIRO Biosecurity Flagship, Australian Animal Health Laboratory, Geelong, Victoria 3220, Australia.
3
Poultry Cooperative Research Centre, University of New England, Armidale, NSW 2351, Australia.
4
Health Sciences Institute, Federal University of Bahia, Salvador, Brazil.
5
Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia rob.moore@rmit.edu.au.
6
School of Science, RMIT University, Bundoora, Australia.

Abstract

Clostridium perfringens is a gastrointestinal pathogen capable of causing disease in a variety of hosts. Necrotic enteritis in chickens is caused by C. perfringens strains that produce the pore-forming toxin NetB, the major virulence factor for this disease. Like many other C. perfringens toxins and antibiotic resistance genes, NetB is encoded on a conjugative plasmid. Conjugative transfer of the netB-containing plasmid pJIR3535 has been demonstrated in vitro with a netB null mutant. This study has investigated the effect of plasmid transfer on disease pathogenesis, with two genetically distinct transconjugants constructed under in vitro conditions, within the intestinal tract of chickens. This study also demonstrates that plasmid transfer can occur naturally in the host gut environment, without the need for antibiotic selective pressure to be applied. The demonstration of plasmid transfer within the chicken host may have implications for disease progression and pathogenesis of C. perfringens-mediated disease. Such horizontal gene transfer events are likely to be common in the clostridia and may be a key factor in strain evolution, both within animals and in the wider environment.ImportanceClostridium perfringens is a major gastrointestinal pathogen of poultry. C. perfringens strains that express the NetB pore-forming toxin, which is encoded on a conjugative plasmid, cause necrotic enteritis. This study demonstrated that the conjugative transfer of the netB containing plasmid to two different non-pathogenic strains converted them into disease causing strains with similar disease-causing capability as the donor strain. Plasmid transfer of netB and antibiotic resistance was also demonstrated to occur within the gastrointestinal tract of chickens, with approximately 14% of isolates recovered comprising of three distinct, in vivo derived, transconjugant types. The demonstration of in vivo plasmid transfer indicates the potential importance of strain plasticity and the contribution of plasmids to strain virulence.

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