title: BEC, a novel enterotoxin of Clostridium perfringens found in human clinical isolates from acute gastroenteritis outbreaks.
abstract: Clostridium perfringens is a causative agent of food-borne gastroenteritis for which C. perfringens enterotoxin (CPE) has been considered an essential factor. Recently, we experienced two outbreaks of food-borne gastroenteritis in which non-CPE producers of C. perfringens were strongly suspected to be the cause. Here, we report a novel enterotoxin produced by C. perfringens isolates, BEC (binary enterotoxin of C. perfringens). Culture supernatants of the C. perfringens strains showed fluid-accumulating activity in rabbit ileal loop and suckling mouse assays. Purification of the enterotoxic substance in the supernatants and high-throughput sequencing of genomic DNA of the strains revealed BEC, composed of BECa and BECb. BECa and BECb displayed limited amino acid sequence similarity to other binary toxin family members, such as the C. perfringens iota toxin. The becAB genes were located on 54.5-kb pCP13-like plasmids. Recombinant BECb (rBECb) alone had fluid-accumulating activity in the suckling mouse assay. Although rBECa alone did not show enterotoxic activity, rBECa enhanced the enterotoxicity of rBECb when simultaneously administered in suckling mice. The entertoxicity of the mutant in which the becB gene was disrupted was dramatically decreased compared to that of the parental strain. rBECa showed an ADP-ribosylating activity on purified actin. Although we have not directly evaluated whether BECb delivers BECa into cells, rounding of Vero cells occurred only when cells were treated with both rBECa and rBECb. These results suggest that BEC is a novel enterotoxin of C. perfringens distinct from CPE, and that BEC-producing C. perfringens strains can be causative agents of acute gastroenteritis in humans. Additionally, the presence of becAB on nearly identical plasmids in distinct lineages of C. perfringens isolates suggests the involvement of horizontal gene transfer in the acquisition of the toxin genes.
authors.affiliation: Division of Bacteriology, Department of Infectious Disease, Osaka Prefectural Institute of Public Health, Osaka, Osaka, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Yonogi
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Matsuda
authors.forename: Takao
authors.initials: T
authors.lastname: Kawai
authors.forename: Tomoko
authors.initials: T
authors.lastname: Yoda
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Harada
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kumeda
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Gotoh
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Hiyoshi
authors.forename: Shota
authors.initials: S
authors.lastname: Nakamura
authors.forename: Toshio
authors.initials: T
authors.lastname: Kodama
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Iida
mesh_terms: D036002:ADP Ribose Transferases / Q000235:genetics; D000208:Acute Disease; D000704:Analysis of Variance; D000818:Animals; D003016:Clostridium perfringens / Q000378:metabolism*; D004195:Disease Models, Animal; D004196:Disease Outbreaks; D004768:Enterotoxins / Q000235:genetics / Q000378:metabolism*; D005759:Gastroenteritis / Q000382:microbiology*; D006801:Humans; D051379:Mice; D008970:Molecular Weight; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: C000620297:BECa protein, Clostridium perfringens; C000620298:BECb protein, Clostridium perfringens; D004768:Enterotoxins; D011994:Recombinant Proteins; C035598:enterotoxin, Clostridium; D036002:ADP Ribose Transferases