Conjugation-Mediated Horizontal Gene Transfer of Clostridium perfringens Plasmids in the Chicken Gastrointestinal Tract Results in the Formation of New Virulent Strains

Abstract

is a gastrointestinal pathogen capable of causing disease in a variety of hosts. Necrotic enteritis in chickens is caused by strains that produce the pore-forming toxin NetB, the major virulence factor for this disease. Like many other toxins and antibiotic resistance genes, NetB is encoded on a conjugative plasmid. Conjugative transfer of the -containing plasmid pJIR3535 has been demonstrated with a null mutant. This study has investigated the effect of plasmid transfer on disease pathogenesis, with two genetically distinct transconjugants constructed under 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 -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. is a major gastrointestinal pathogen of poultry. 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 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 and antibiotic resistance was also demonstrated to occur within the gastrointestinal tract of chickens, with approximately 14% of isolates recovered comprising of three distinct, derived, transconjugant types. The demonstration of plasmid transfer indicates the potential importance of strain plasticity and the contribution of plasmids to strain virulence.

In silico Identification of Novel Toxin Homologs and Associated Mobile Genetic Elements in Clostridium perfringens

“…However, toxin typing does not account for the full toxin repertoire a strain may be capable of producing and therefore lacks the high resolution afforded with whole genome sequencing (WGS). Furthermore, the clostridial toxin typing system does not account for strain clonality and is inappropriate for inference of evolutionary relationships [2] as many of the toxins are encoded on large plasmids [3] and capable of horizontal gene transfer [4,5,6].…”

“…Due to the specificity of many C. perfringens isolates to particular animal hosts and disease outcomes, and the diverse pan-genome of the species [4,25], we hypothesize that only a subset of the potential toxins encoded by C. perfringens have been identified. The aim of this study was to bioinformatically identify novel virulence-associated genes in previously characterised C. perfringens strains to inform and refine future studies, as well as narrow down potential drug or vaccine targets.…”

Mechanisms of Action and Cell Death Associated with Clostridium perfringens Toxins

“…The netB gene is located on a 42 kb pathogenicity locus named NELoc1, present on large, conjugative plasmids [ 154 , 155 , 156 , 157 ]. Like CPB, NetB shares partial sequence similarity with a β-PFT, named alpha hemolysin, from S. aureus [ 158 ].…”

Evolutionary Features in the Structure and Function of Bacterial Toxins

“…Introduction of a new gene to other organism involves either complete or partial replacement of the incumbent gene. Using HGT C. difficile and C. perfringens are capable of converting a non-toxigenic strain to a toxin producer [121,122]. However, in most cases, this process involves transfer of totally new set of genes to the host genome.…”