Role of the Agr-Like Quorum-Sensing System in Regulating Toxin Production by Clostridium perfringens Type B Strains CN1793 and CN1795

Abstract

ABSTRACTClostridium perfringenstype B causes enteritis and enterotoxemia in domestic animals. By definition, these bacteria must produce alpha toxin (CPA), beta toxin (CPB) and epsilon toxin (ETX) although most type B strains also produce perfringolysin O (PFO) and beta2 toxin (CPB2). A recently identified Agr-like quorum-sensing (QS) system inC. perfringenscontrols all toxin production by surveyed type A, C, and D strains, but whether this QS is involved in regulating toxin production by type B strains has not been explored. Therefore, the current study introducedagrBnull mutations into type B strains CN1795 and CN1793. Both type BagrBnull mutants exhibited reduced levels of CPB, PFO, and CPA in their culture supernatants, and this effect was reversible by complementation. The reduced presence of CPB in culture supernatant involved decreasedcpbtranscription. In contrast, theagrBnull mutants of both type B strains retained wild-type production levels of ETX and CPB2. In a Caco-2 cell model of enteritis, culture supernatants of the type BagrBnull mutants were less cytotoxic than supernatants of their wild-type parents. However, in an MDCK cellin vitromodel for enterotoxemic effects, supernatants from theagrBnull mutants or wild-type parents were equally cytotoxic after trypsin activation. Coupling these and previous results, it is now evident that strain-dependent variations exist in Agr-like QS system regulation ofC. perfringenstoxin production. The cell culture results further support a role for trypsin in determining which toxins contribute to disease involving type B strains.