Prevalence of netB among some clinical isolates of Clostridium perfringens from animals in the United States.
ABSTRACT A previously unknown pore forming toxin, called NetB toxin, which is produced by some Australian strains of Clostridium perfringens has recently been reported. This toxin was reported to be critical to the development of the disease necrotic enteritis, in chickens. To investigate the occurrence of the toxin gene (netB) in non-Australian C. perfringens strains, one hundred and six American isolates of C. perfringens were examined. Ninety-two isolates were from chickens, and 14 were from cattle. The netB gene was found in 14 isolates from chickens (7 from chickens with necrotic enteritis, and 7 from unrelated chickens with no evidence of necrotic enteritis). The netB gene was also detected in an isolate recovered from a 3-year-old cow with liver abscesses. The products of all positive netB PCR reactions were sequenced, and these showed 100% nucleotide identity to the netB sequence published in GenBank. Five isolates which had been recovered from five chickens with necrotic enteritis (from four flocks) were netB negative. An additional 24 isolates recovered from one of these lesioned chickens were also netB negative. The present study represents the first study of C. perfringens isolates outside Australia for netB, and the first identification of netB in an isolate from a species other than chickens. The results indicate that the role of NetB in the induction of necrotic enteritis needs to be further investigated, by determining the disease producing capability of both netB positive strains recovered from normal chickens, and netB negative strains recovered from chickens with necrotic enteritis.
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ABSTRACT: NetB (necrotic enteritis toxin B) is a recently identified β-pore-forming toxin produced by Clostridium perfringens. This toxin has been shown to play a major role in avian necrotic enteritis. In recent years, a dramatic increase in necrotic enteritis has been observed, especially in countries where the use of antimicrobial growth promoters in animal feedstuffs has been banned. The aim of this work was to determine whether immunisation with a NetB toxoid would provide protection against necrotic enteritis. The immunisation of poultry with a formaldehyde NetB toxoid or with a NetB genetic toxoid (W262A) resulted in the induction of antibody responses against NetB and provided partial protection against disease.Vaccine 05/2013; · 3.77 Impact Factor
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ABSTRACT: SUMMARY In both humans and animals, Clostridium perfringens is an important cause of histotoxic infections and diseases originating in the intestines, such as enteritis and enterotoxemia. The virulence of this Gram-positive, anaerobic bacterium is heavily dependent upon its prolific toxin-producing ability. Many of the ∼16 toxins produced by C. perfringens are encoded by large plasmids that range in size from ∼45 kb to ∼140 kb. These plasmid-encoded toxins are often closely associated with mobile elements. A C. perfringens strain can carry up to three different toxin plasmids, with a single plasmid carrying up to three distinct toxin genes. Molecular Koch's postulate analyses have established the importance of several plasmid-encoded toxins when C. perfringens disease strains cause enteritis or enterotoxemias. Many toxin plasmids are closely related, suggesting a common evolutionary origin. In particular, most toxin plasmids and some antibiotic resistance plasmids of C. perfringens share an ∼35-kb region containing a Tn916-related conjugation locus named tcp (transfer of clostridial plasmids). This tcp locus can mediate highly efficient conjugative transfer of these toxin or resistance plasmids. For example, conjugative transfer of a toxin plasmid from an infecting strain to C. perfringens normal intestinal flora strains may help to amplify and prolong an infection. Therefore, the presence of toxin genes on conjugative plasmids, particularly in association with insertion sequences that may mobilize these toxin genes, likely provides C. perfringens with considerable virulence plasticity and adaptability when it causes diseases originating in the gastrointestinal tract.Microbiology and molecular biology reviews: MMBR 06/2013; 77(2):208-233. · 12.59 Impact Factor
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ABSTRACT: NetB toxin from Clostridium perfringens is a major virulence factor in necrotic enteritis in poultry. In this study the efficacy of NetB as a vaccine antigen to protect chickens from necrotic enteritis was examined. Broiler chickens were immunized subcutaneously with purified recombinant NetB (rNetB), formalin treated bacterin and cell free toxoid with or without rNetB supplementation. Intestinal lesion scores and NetB antibody levels were measured to determine protection after mild oral gavage, moderate in-feed and heavy in-feed challenges with virulent C. perfringens isolates. Birds immunized with rNetB were significantly protected against necrotic enteritis when challenged with a mild oral dose of virulent bacteria, but were not protected when a more robust challenge was used. Bacterin and cell free toxoid without rNetB supplementation did not protect birds from moderate and severe in-feed challenge. Only birds immunized with bacterin and cell free toxoid supplemented with rNetB showed significant protection against moderate and severe in-feed challenge, with the later giving the greatest protection. Higher NetB antibody titres were observed in birds immunized with rNetB compared to those vaccinated with bacterin or toxoid, suggesting that the in vitro levels of NetB produced by virulent C. perfringens isolates are too low to induce the development of a strong immune response. These results suggest that vaccination with NetB alone may not be sufficient to protect birds from necrotic enteritis in the field, but that in combination with other cellular or cell-free antigens it can significantly protect chickens from disease.Veterinary Research 07/2013; 44(1):54. · 3.43 Impact Factor