Clostridium perfringens type A: in vitro system for sporulation and enterotoxin synthesis

Spread of a large plasmid carrying thecpegene and thetcplocus amongstClostridium perfringensisolates from nosocomial outbreaks and sporadic cases of gastroenteritis in a geriatric hospital

To investigate two clusters of diarrhoea cases observed in our geriatric hospital wards, the faecal specimens were analysed. Reversed passive latex agglutination assay revealed that 63·2% and 41·7% of the faecal specimens from each cluster were positive forClostridium perfringensenterotoxin. PCR assay revealed that 71·4% and 68·8% ofC. perfringensisolates from each cluster were positive for the enterotoxin gene (cpe). These observations suggested that both the clusters were outbreaks caused by enterotoxigenicC. perfringens. Subsequent pulsed-field gel electrophoresis analysis revealed that the two outbreaks were caused by differentC. perfringensisolates. However, these outbreak isolates as well as other sporadic diarrhoea isolates shared a 75-kb plasmid on which thecpegene and thetcplocus were located. The 75-kb plasmid had horizontally spread to variousC. perfringensisolates and had caused outbreaks and sporadic infections. However, the site and time of the plasmid transfer are unclear.

Cloning, nucleotide sequencing, and expression of the Clostridium perfringens enterotoxin gene in Escherichia coli

A complete copy of the gene (cpe) encoding Clostridium perfringens enterotoxin (CPE), an important virulence factor involved in C. perfringens food poisoning and other gastrointestinal illnesses, has been cloned, sequenced, and expressed in Escherichia coli. The cpe gene was shown to encode a 319-amino-acid polypeptide with a deduced molecular weight of 35,317. There was no consensus sequence for a typical signal peptide present in the 5' region of cpe. Cell lysates from recombinant cpe-positive E. coli were shown by quantitative immunoblot analysis to contain moderate amounts of CPE, and this recombinant CPE was equal to native CPE in cytotoxicity for mammalian Vero cells. CPE expression in recombinant E. coli appeared to be largely driven from a clostridial promoter. Immunoblot analysis also demonstrated very low levels of CPE in vegetative cell lysates of enterotoxin-positive C. perfringens. However, when the same C. perfringens strain was induced to sporulate, much stronger CPE expression was detected in these sporulating cells than in either vegetative C. perfringens cells or recombinant E. coli. Collectively, these results strongly suggest that sporulation is not essential for cpe expression, but sporulation does facilitate high-level cpe expression.

Enterotoxin synthesis by nonsporulating cultures of Clostridium perfringens

Chemostat-cultured Clostridium perfringens ATCC 3624 and NCTC 10240, and a nonsporulating mutant strain, 8-5, produced enterotoxin in the absence of sporulation when cultured in a chemically defined medium at a 0.084-h-1 dilution rate at 37 degrees C. The enterotoxin was detected by serological and biological assays. Examination of the chemostat cultures by electron microscopy did not reveal sporulation at any stage. The culture maintained enterotoxigenicity throughout cultivation in a continuous system. The enterotoxin was detected in batch cultures of each strain cultivated in fluid thioglycolate medium and a chemically defined medium. No heat-resistant or light-refractile spores were detected in batch cultures during the exponential growth.