Abstract
ObjectiveClostridium perfringens causes gastrointestinal diseases in both humans and domestic animals. Type A strains expressing the NetB toxin are the main cause of necrotic enteritis (NE) in chickens, which has remarkable impact on animal welfare and production economy in the international poultry industry. Three pathogenicity loci NELoc-1, -2 and -3 and a collagen adhesion gene cnaA have been found to be associated with NE in chickens, whereas the presence of these has not been investigated in diseased turkeys. The purpose was to investigate the virulence associated genome content and the genetic relationship among 30 C. perfringens isolates from both healthy and NE infected chickens and turkeys, applying whole-genome sequencing.ResultsNELoc-1, -3, netB and cnaA were significantly associated with NE isolates from chickens, whereas only NELoc-2 was commonly observed in both diseased turkeys and chickens. A putative collagen adhesion gene that encodes a von Willebrand Factor (vWF) domain was identified in all diseased turkeys and designated as cnaD. The phylogenetic analysis based on single nucleotide polymorphisms showed that the isolates generally were not closely related. These results indicate that virulence factors and pathogenicity loci associated with NE in chickens are not important to the same extent in diseased turkeys except for NELoc-2. A putative collagen adhesion gene which potentially could be of importance in regard to the NE pathogenesis in turkeys was identified and need to be further investigated. Thus, the pathogenesis of NE in turkeys appears to be different from that of broiler chickens.
Highlights
Clostridium perfringens is a Gram-positive anaerobic bacterium that causes gastrointestinal diseases in humans and domestic animals [1]
necrotic enteritis locus (NELoc)-1, -3, netB and cnaA were significantly associated with necrotic enteritis (NE) isolates from chickens, whereas only NELoc-2 was commonly observed in both diseased turkeys and chickens
These results indicate that virulence factors and pathogenicity loci associated with NE in chickens are not important to the same extent in diseased turkeys except for NELoc-2
Summary
Of the 30 isolates, 21 were sequenced to an average coverage of >80× whereas the rest had an average coverage of >40× except isolate T43 that had >30×. The NELoc-1 and -3 associated genes (Additional file 3), were primarily observed among isolates from diseased chickens (Table 1). The NELoc-3 HPGs had 77% (10/13) of NE isolates from chickens and in a single isolate (1/9) from a diseased turkeys (p = 0.0075). Two isolates from healthy chickens and a single isolate from a healthy turkey carried NELoc-2 (Table 1). The investigation of the general gene content showed a putative collagen adhesion gene of 2787 nucleotides (NTs) (Additional file 5) here labelled cnaD, which was present in all isolates from diseased turkeys (9/9) but only in 39% (5/13) of diseased chickens (p = 0.0055). The best hit was an identical C. perfringens protein of 928 AAs (NCBI Accession No WP_011590364) with a query coverage of 100% and an AA identity of 100% This protein contained two types of conserved domains. A single von Willebrand Factor (vWF) type A domain of 142 AAs (NCBI accession no. smart00327) and three Cna protein B-type domains each of 63 AAs (NCBI accession no. pfam05738)
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