Clostridium perfringens type B and D strains cause enterotoxemias and enteritis in livestock after proliferating in the intestines and producing epsilon-toxin (ETX), alpha-toxin (CPA), and, usually, perfringolysin O (PFO). Although ETX is one of the most potent bacterial toxins, the regulation of ETX production by type B or D strains remains poorly understood. The present work determined that the type D strain CN3718 upregulates production of ETX upon close contact with enterocyte-like Caco-2 cells. This host cell-induced upregulation of ETX expression was mediated at the transcriptional level. Using an isogenic agrB null mutant and complemented strain, the agr operon was shown to be required when CN3718 produces ETX in broth culture or, via a secreted signal consistent with a quorum-sensing (QS) effect, upregulates ETX production upon contact with host cells. These findings provide the first insights into the regulation of ETX production, as well as additional evidence that the Agr-like QS system functions as a global regulator of C. perfringens toxin production.

Since it was proposed previously that the Agr-like QS system regulates C. perfringens gene expression via the VirS/VirR two-component regulatory system, an isogenic virR null mutant of CN3718 was constructed to evaluate the importance of VirS/VirR for CN3718 toxin production. This mutation affected production of CPA and PFO, but not ETX, by CN3718. These results provide the first indication that C. perfringens toxin expression regulation by the Agr-like quorum-sensing system may not always act via the VirS/VirR two-component system. Mechanisms by which Clostridium perfringens type B and D strains regulate production of epsilon-toxin (ETX), a CDC class B select toxin, are poorly understood. Production of several other toxins expressed by C. perfringens is wholly or partially regulated by both the Agr-like quorum-sensing (QS) system and the VirS/VirR two-component regulatory system, so the present study tested whether ETX expression by type D strain CN3718 also requires these regulatory systems. The agr operon was shown to be essential for signaling CN3718 to produce ETX in broth culture or to upregulate ETX production upon close contact with enterocyte-like Caco-2 cells, which may have pathogenic relevance since ETX is produced intestinally. However, ETX production remained at wild-type levels after inactivation of the VirS/VirR system in CN3718.

These findings provide the first information regarding regulation of ETX production and suggest Agr-like QS toxin production regulation in C. perfringens does not always require the VirS/VirR system. 1000 Most Important Words Norman Schur Pdf Free. Introduction The Gram-positive, spore-forming, anaerobic bacterium Clostridium perfringens is an important pathogen of humans and livestock, causing clostridial myonecrosis and numerous diseases originating in the intestines (, ). C. perfringens virulence is largely dependent upon prolific toxin production, with this bacterium capable of producing at least 17 different toxins. However, only portions of this toxin arsenal are produced by individual strains, which allows for a toxinotyping classification (A to E) system based upon the production of alpha-toxin (CPA), beta-toxin, epsilon-toxin (ETX), and iota-toxin (, ). By definition, C. perfringens type D strains must produce alpha-toxin (CPA) and epsilon-toxin (ETX). Difference Between Positivism And Interpretivism Pdf To Jpg more. Some type D strains also produce additional toxins, such as perfringolysin O (PFO), that are not used for toxin typing ().

C. perfringens type D isolates cause often fatal enterotoxemias in several livestock species, as well as acute or chronic enteritis in goats (, ). During type D enterotoxemias, toxins are produced in the intestines and then absorbed through the intestinal mucosa into the circulation, where they spread to other internal organs (). This enterotoxemia then causes edema in several organs, notably the brain, kidneys, lungs, and liver. An important feature of C. perfringens pathogenicity is the correlation between different toxin types and pathologies, strongly suggesting that particular toxins are important for certain diseases.

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File Scavenger Crack Torrent Download. ETX, an ~30-kDa pore-forming protein, is considered a major virulence factor of both type B and D strains (, ). Ranking as the third most potent clostridial toxin after the botulinum and tetanus toxins, ETX is listed as a class B CDC select toxin. Epsilon-toxin is normally produced as an inactive ~33-kDa prototoxin, but after proteolytic hydrolysis by intestinal proteases (such as trypsin and chymotrypsin) or lambda-toxin produced by C. perfringens, this prototoxin is converted into a fully active toxin (, ). Intensive studies over the past 20 years have provided an understanding of the structure, mode of action, and genetics of many C. perfringens toxins (, ).