Ileal loop fluid accumulation and production of diarrhea in rabbits by cell-free products of Clostridium perfringens

The biology and pathogenicity of Clostridium perfringens type F: a common human enteropathogen with a new(ish) name

SUMMARYIn the 2018-revised Clostridium perfringens typing classification system, isolates carrying the enterotoxin (cpe) and alpha toxin genes but no other typing toxin genes are now designated as type F. Type F isolates cause food poisoning and nonfoodborne human gastrointestinal (GI) diseases, which most commonly involve type F isolates carrying, respectivefooly, a chromosomal or plasmid-borne cpe gene. Compared to spores of other C. perfringens isolates, spores of type F chromosomal cpe isolates often exhibit greater resistance to food environment stresses, likely facilitating their survival in improperly prepared or stored foods. Multiple factors contribute to this spore resistance phenotype, including the production of a variant small acid-soluble protein-4. The pathogenicity of type F isolates involves sporulation-dependent C. perfringens enterotoxin (CPE) production. C. perfringens sporulation is initiated by orphan histidine kinases and sporulation-associated sigma factors that drive cpe transcription. CPE-induced cytotoxicity starts when CPE binds to claudin receptors to form a small complex (which also includes nonreceptor claudins). Approximately six small complexes oligomerize on the host cell plasma membrane surface to form a prepore. CPE molecules in that prepore apparently extend β-hairpin loops to form a β-barrel pore, allowing a Ca2+ influx that activates calpain. With low-dose CPE treatment, caspase-3-dependent apoptosis develops, while high-CPE dose treatment induces necroptosis. Those effects cause histologic damage along with fluid and electrolyte losses from the colon and small intestine. Sialidases likely contribute to type F disease by enhancing CPE action and, for NanI-producing nonfoodborne human GI disease isolates, increasing intestinal growth and colonization.

In vitro and ex vivo modeling of enteric bacterial infections

Enteric bacterial infections contribute substantially to global disease burden and mortality, particularly in the developing world. In vitro 2D monolayer cultures have provided critical insights into the fundamental virulence mechanisms of a multitude of pathogens, including Salmonella enterica serovars Typhimurium and Typhi, Vibrio cholerae, Shigella spp., Escherichia coli and Campylobacter jejuni, which have led to the identification of novel targets for antimicrobial therapy and vaccines. In recent years, the arsenal of experimental systems to study intestinal infections has been expanded by a multitude of more complex models, which have allowed to evaluate the effects of additional physiological and biological parameters on infectivity. Organoids recapitulate the cellular complexity of the human intestinal epithelium while 3D bioengineered scaffolds and microphysiological devices allow to emulate oxygen gradients, flow and peristalsis, as well as the formation and maintenance of stable and physiologically relevant microbial diversity. Additionally, advancements in ex vivo cultures and intravital imaging have opened new possibilities to study the effects of enteric pathogens on fluid secretion, barrier integrity and immune cell surveillance in the intact intestine. This review aims to present a balanced and updated overview of current intestinal in vitro and ex vivo methods for modeling of enteric bacterial infections. We conclude that the different paradigms are complements rather than replacements and their combined use promises to further our understanding of host-microbe interactions and their impacts on intestinal health.

Enterotoxic Clostridia: Clostridium perfringens Enteric Diseases

In humans and livestock, Clostridium perfringens is an important cause of intestinal infections that manifest as enteritis, enterocolitis, or enterotoxemia. This virulence is largely related to the toxin-producing ability of C. perfringens. This article primarily focuses on the C. perfringens type F strains that cause a very common type of human food poisoning and many cases of nonfoodborne human gastrointestinal diseases. The enteric virulence of type F strains is dependent on their ability to produce C. perfringens enterotoxin (CPE). CPE has a unique amino acid sequence but belongs structurally to the aerolysin pore-forming toxin family. The action of CPE begins with binding of the toxin to claudin receptors, followed by oligomerization of the bound toxin into a prepore on the host membrane surface. Each CPE molecule in the prepore then extends a beta-hairpin to form, collectively, a beta-barrel membrane pore that kills cells by increasing calcium influx. The cpe gene is typically encoded on the chromosome of type F food poisoning strains but is encoded by conjugative plasmids in nonfoodborne human gastrointestinal disease type F strains. During disease, CPE is produced when C. perfringens sporulates in the intestines. Beyond type F strains, C. perfringens type C strains producing beta-toxin and type A strains producing a toxin named CPILE or BEC have been associated with human intestinal infections. C. perfringens is also an important cause of enteritis, enterocolitis, and enterotoxemia in livestock and poultry due to intestinal growth and toxin production.

Animal models to study the pathogenesis of human and animal Clostridium perfringens infections

The most common animal models used to study Clostridium perfringens infections in humans and animals are reviewed here. The classical C. perfringens-mediated histotoxic disease of humans is clostridial myonecrosis or gas gangrene and the use of a mouse myonecrosis model coupled with genetic studies has contributed greatly to our understanding of disease pathogenesis. Similarly, the use of a chicken model has enhanced our understanding of type A-mediated necrotic enteritis in poultry and has led to the identification of NetB as the primary toxin involved in disease. C. perfringens type A food poisoning is a highly prevalent bacterial illness in the USA and elsewhere. Rabbits and mice are the species most commonly used to study the action of enterotoxin, the causative toxin. Other animal models used to study the effect of this toxin are rats, non-human primates, sheep and cattle. In rabbits and mice, CPE produces severe necrosis of the small intestinal epithelium along with fluid accumulation. C. perfringens type D infection has been studied by inoculating epsilon toxin (ETX) intravenously into mice, rats, sheep, goats and cattle, and by intraduodenal inoculation of whole cultures of this microorganism in mice, sheep, goats and cattle. Molecular Koch's postulates have been fulfilled for enterotoxigenic C. perfringens type A in rabbits and mice, for C. perfringens type A necrotic enteritis and gas gangrene in chickens and mice, respectively, for C. perfringens type C in mice, rabbits and goats, and for C. perfringens type D in mice, sheep and goats.

Animal models to study the pathogenesis of enterotoxigenic Clostridium perfringens infections

Rabbits, mice, rats, non-human primates, sheep and cattle have been used to study the effect of Clostridium perfringens enterotoxin (CPE). CPE produces mostly necrosis of the small intestinal epithelium along with fluid accumulation in rabbits and mice. In the latter, CPE can bind to internal organs such as the liver, which induces lethal potassium levels in blood.

Development and application of a mouse intestinal loop model to study the in vivo action of Clostridium perfringens enterotoxin

Clostridium perfringens enterotoxin (CPE) is responsible for causing the gastrointestinal symptoms of C. perfringens type A food poisoning, the second most commonly identified bacterial food-borne illness in the United States. CPE is produced by sporulating C. perfringens cells in the small intestinal lumen, where it then causes epithelial cell damage and villous blunting that leads to diarrhea and cramping. Those effects are typically self-limiting; however, severe outbreaks of this food poisoning, particularly two occurring in psychiatric institutions, have involved deaths. Since animal models are currently limited for the study of the CPE action, a mouse ligated intestinal loop model was developed. With this model, significant lethality was observed after 2 h in loops receiving an inoculum of 100 or 200 μg of CPE but not using a 50-μg toxin inoculum. A correlation was noted between the overall intestinal histological damage and lethality in mice. Serum analysis revealed a dose-dependent increase in serum CPE and potassium levels. CPE binding to the liver and kidney was detected, along with elevated levels of potassium in the serum. These data suggest that CPE can be absorbed from the intestine into the circulation, followed by the binding of the toxin to internal organs to induce potassium leakage, which can cause death. Finally, CPE pore complexes similar to those formed in tissue culture cells were detected in the intestine and liver, suggesting that (i) CPE actions are similar in vivo and in vitro and (ii) CPE-induced potassium release into blood may result from CPE pore formation in internal organs such as the liver.

Clostridium perfringens Type A Food Poisoning II. Response of the Rabbit Ileum as an Indication of Enteropathogenicity of Strains of Clostridium perfringens in Human Beings

The effect of feeding human beings individual strains of Clostridium perfringens or culture filtrates thereof was examined. The strains selected for challenge included both those which had previously been shown to produce fluid accumulation in the ligated ileum or overt diarrhea when injected into the nonligated ileum of the rabbit, or had produced both, and those which did not regularly produce these responses. Challenge doses prepared by allowing each strain to grow in beef stew for 3 hr at 46 C resulted in a 61% incidence of diarrhea when rabbit-positive cells were used. No diarrhea occurred among the subjects fed rabbit-negative strains prepared in a similar manner. The procedures employed in preparing the challenge dose appeared to influence the results obtained. When cell-free filtrates were fed, 4 of 15 persons consuming filtrates from rabbit-positive strains developed diarrhea. All subjects fed filtrates from rabbit-negative strains remained free from diarrhea. Serological tests were carried out to compare the identity of the strains of C. perfringens consumed by the subjects and those excreted in the feces. Heat resistance measured as D(100) values varied greatly among the rabbit-positive strains.

Mechanism of Action of the Enteropathogenic Factor of Clostridium perfringens Type A

Cell extract of an enteropathogenic strain of Clostridium perfringens type A was administered intravenously to lambs, rabbits, and guinea pigs. Lambs developed transitory diarrhea, lacrimation, salivation, nasal discharge, lassitude, and dyspnea in 1 to 5 hr after inoculation. Large doses of the inoculum caused rapid onset of the clinical signs and subsequent death. Examination of dead animals revealed intensely hyperemic small intestinal mucosa and some congestion in the liver, lungs, spleen, and kidneys. Rabbits showed excessive salivation, frequent defecation, tranquility, and dyspnea, followed by death. Guinea pigs became weak and died in 15 min to 7 hr. Congestion was evident in lungs, liver, spleen, and in the small intestine. In lambs and guinea pigs tested, atropine and epinephrine alleviated the clinical signs. Intradermally injected cell extract caused an immediate increase in capillary permeability and subsequent erythematous reaction without necrosis in the skin of guinea pigs. It is hypothesized that in the enteric infection C. perfringens enteropathogenic factor acts on the small intestine causing increased capillary permeability, vasodilation, and increased intestinal motility.

In Vivo Effects of Clostridium perfringens Enteropathogenic Factors on the Rat Ileum

An experimental model was established using the terminal ileum of the rat for characterizing and studying the effects of crude cell-free extract from Clostridium perfringens upon physiological and histological parameters involved in the transport process. Further work was done with the model system using purified enterotoxin (protein) from the cell extract. Using an in vivo perfusion technique it was found that crude extract induces a reversal of net transport, from absorption in controls to secretion, of water, sodium, and chloride. Glucose absorption was greatly inhibited, whereas potassium and bicarbonate transports were unaffected. Crude extract also caused histological damage to the villus epithelium by denuding the villus tips, thereby leaving the lamina propria exposed. Similar responses in transport of water, sodium, chloride, bicarbonate, and glucose were caused by purified toxin. Little or no histological damage resulted from the pure toxin activity. However, the toxin was shown to have the capacity to denude villus tips under the proper experimental conditions.

Clostridium perfringens Type A Food Poisoning I. Response of the Rabbit Ileum as an Indication of Enteropathogenicity of Strains of Clostridium perfringens in Monkeys

Diarrhea and vomiting have been experimentally produced in monkeys after oral challenge with viable cells or culture filtrates of certain strains of Clostridium perfringens that previously had been shown to produce either fluid accumulation in the ligated ileum or overt diarrhea in the nonligated ileum of the rabbit, or both. Strains (or their culture filtrates) which did not produce a response in the rabbit likewise produced no symptoms in monkeys.

Sporulation and enterotoxin (CPE) synthesis are controlled by the sporulation-specific sigma factors SigE and SigK in Clostridium perfringens

Clostridium perfringens is the third most frequent cause of bacterial food poisoning annually in the United States. Ingested C. perfringens vegetative cells sporulate in the intestinal tract and produce an enterotoxin (CPE) that is responsible for the symptoms of acute food poisoning. Studies of Bacillus subtilis have shown that gene expression during sporulation is compartmentalized, with different genes expressed in the mother cell and the forespore. The cell-specific RNA polymerase sigma factors sigma(F), sigma(E), sigma(G), and sigma(K) coordinate much of the developmental process. The C. perfringens cpe gene, encoding CPE, is transcribed from three promoters, where P1 was proposed to be sigma(K) dependent, while P2 and P3 were proposed to be sigma(E) dependent based on consensus promoter recognition sequences. In this study, mutations were introduced into the sigE and sigK genes of C. perfringens. With the sigE and sigK mutants, gusA fusion assays indicated that there was no expression of cpe in either mutant. Results from gusA fusion assays and immunoblotting experiments indicate that sigma(E)-associated RNA polymerase and sigma(K)-associated RNA polymerase coregulate each other's expression. Transcription and translation of the spoIIID gene in C. perfringens were not affected by mutations in sigE and sigK, which differs from B. subtilis, in which spoIIID transcription requires sigma(E)-associated RNA polymerase. The results presented here show that the regulation of developmental events in the mother cell compartment of C. perfringens is not the same as that in B. subtilis and Clostridium acetobutylicum.

Influence of peptone source on sporulation of Clostridium perfringens type A

Clostridium perfringens is a foodborne disease agent that produces a sporulation-specific enterotoxin. To produce enterotoxin for experimental purposes or spores for challenge or physiological studies, the use of a convenient sporulation medium is required. The most commonly used is Duncan-Strong medium. Few isolates sporulate at high levels in this medium. We investigated the effectiveness of peptones from a variety of sources on the sporulation of this organism compared with the peptone in the original formulation, proteose peptone (control). Seven strains were used to screen 32 peptones, with starch or raffinose as the carbohydrate source. In most cases, raffinose was more effective than starch in stimulating sporulation, confirming our previous study. Two promising peptones, potato peptone, and Proteose Peptone no. 3, were selected and tested against 49 additional enterotoxin-positive and -negative strains, with raffinose as the carbohydrate. For 49 strains, 5 sporulated best (>10%) in the control peptone, 6 sporulated best in Peptone no. 3, and 23 sporulated best in the potato peptone. Of the 23 strains, 16 sporulated at levels 25% more than the control peptone. The increase in sporulation rates was reflected in the enterotoxin and heat-resistant spore levels. The methylxanthines caffeine and theobromine were effective in increasing the sporulation of less than half of 19 enterotoxin-positive strains. Our results suggest that the replacement of proteose peptone with potato peptone be considered if difficulty in obtaining spores of specific strains of C. perfringens is encountered.

Identification and characterization of Clostridium perfringens using single target DNA microarray chip

A DNA microarray method was developed to identify the presence of toxin genes: encoding beta toxin (cpb), epsilon toxin (etx), enterotoxin (cpe), alpha toxin (cpa), and iota toxin (iA) in Clostridium perfringens. To build the DNA chip, each gene sequence was represented by one approximately 22-bp amino-modified oligonucleotide printed twice on aldehyde-coated slides. Multiplex PCR with Cy3 and Cy5-dCTP derivatized fluorescent nucleotides was used to label five genes and fluorescent probes were prepared. The PCR probes were denatured and single-strand-labeled DNAs were separated and purified using magnetic beads. The presence of toxin genes in C. perfringens was detected by hybridization of amplified ssDNA probes to oligonucleotides on the chip representing one target sequence of each toxin gene. The DNA chip was able to identify eight strains of C. perfringens.

Cloning and sequence analysis of a novel metalloprotease gene from Vibrio parahaemolyticus 04

The metalloprotease gene (vppC) from Vibrio parahaemolyticus 04 has been cloned and sequenced. The vppC gene contains an open reading frame of 2442 nucleotides encoding a polypeptide of 814 amino acids with a calculated molecular mass of 89,833 Da. The predicted amino acid sequence of VppC containing a zinc metalloprotease HEXXH consensus motif displays extensive homology to the collagenase from Vibrio alginolyticus. The activity of the recombinant protease produced in Escherichia coli was examined by gelatin zymography and proteolytic activity assays. The substrate specificity study showed that the type I collagen and synthetic collagenase substrate carbobenzoxy-glycyl-L-prolyl-glycyl-glycyl-L-prolyl-L-alanine were the best substrates, indicating that the cloned metalloprotease is indeed a collagenase. Multiple alignment analysis of the amino acid sequences and the enzymatic properties such as molecular mass and substrate specificity revealed three distinct classes of Vibrio metalloproteases. The identification of a new metalloprotease gene expands the role of Vibrio metalloproteases as a virulence factor for host infection.

Comparative experiments to examine the effects of heating on vegetative cells and spores of Clostridium perfringens isolates carrying plasmid genes versus chromosomal enterotoxin genes

Clostridium perfringens enterotoxin (CPE) is an important virulence factor for both C. perfringens type A food poisoning and several non-food-borne human gastrointestinal diseases. Recent studies have indicated that C. perfringens isolates associated with food poisoning carry a chromosomal cpe gene, while non-food-borne human gastrointestinal disease isolates carry a plasmid cpe gene. However, no explanation has been provided for the strong associations between certain cpe genotypes and particular CPE-associated diseases. Since C. perfringens food poisoning usually involves cooked meat products, we hypothesized that chromosomal cpe isolates are so strongly associated with food poisoning because (i) they are more heat resistant than plasmid cpe isolates, (ii) heating induces loss of the cpe plasmid, or (iii) heating induces migration of the plasmid cpe gene to the chromosome. When we tested these hypotheses, vegetative cells of chromosomal cpe isolates were found to exhibit, on average approximately twofold-higher decimal reduction values (D values) at 55 degrees C than vegetative cells of plasmid cpe isolates exhibited. Furthermore, the spores of chromosomal cpe isolates had, on average, approximately 60-fold-higher D values at 100 degrees C than the spores of plasmid cpe isolates had. Southern hybridization and CPE Western blot analyses demonstrated that all survivors of heating retained their cpe gene in its original plasmid or chromosomal location and could still express CPE. These results suggest that chromosomal cpe isolates are strongly associated with food poisoning, at least in part, because their cells and spores possess a high degree of heat resistance, which should enhance their survival in incompletely cooked or inadequately warmed foods.

Inactivation of the gene (cpe) encoding Clostridium perfringens enterotoxin eliminates the ability of two cpe-positive C. perfringens type A human gastrointestinal disease isolates to affect rabbit ileal loops

Previous epidemiological studies have implicated Clostridium perfringens enterotoxin (CPE) as a virulence factor in the pathogenesis of several gastrointestinal (GI) illnesses caused by C. perfringens type A isolates, including C. perfringens type A food poisoning and non-food-borne GI illnesses, such as antibiotic-associated diarrhoea and sporadic diarrhoea. To further evaluate the importance of CPE in the pathogenesis of these GI diseases, allelic exchange was used to construct cpe knock-out mutants in both SM101 (a derivative of a C. perfringens type A food poisoning isolate carrying a chromosomal cpe gene) and F4969 (a C. perfringens type A non-food-borne GI disease isolate carrying a plasmid-borne cpe gene). Western blot analyses confirmed that neither cpe knock-out mutant could express CPE during either sporulation or vegetative growth, and that this lack of CPE expression could be complemented by transforming these mutants with a recombinant plasmid carrying the wild-type cpe gene. When the virulence of the wild-type, mutant and complementing strains were compared in a rabbit ileal loop model, sporulating (but not vegetative) culture lysates of the wild-type isolates induced significant ileal loop fluid accumulation and intestinal histopathological damage, but neither sporulating nor vegetative culture lysates of the cpe knock-out mutants induced these intestinal effects. However, full sporulation-associated virulence could be restored by complementing these cpe knock-out mutants with a recombinant plasmid carrying the wild-type cpe gene, which confirms that the observed loss of virulence for the cpe knock-out mutants results from the specific inactivation of the cpe gene and the resultant loss of CPE expression. Therefore, in vivo analysis of our isogenic cpe mutants indicates that CPE expression is necessary for these two cpe-positive C. perfringens type A human disease isolates to cause GI effects in the culture lysate:ileal loop model system, a finding that supports CPE as an important virulence factor in GI diseases involving cpe-positive C. perfringens type A isolates.

Expression from the Clostridium perfringens cpe promoter in C. perfringens and Bacillus subtilis

Clostridium perfringens is a source of food poisoning in humans and animals because of production of a potent enterotoxin (CPE). To study the regulation of the cpe gene in C. perfringens, we cloned and sequenced the cpe promoter regions and N-terminal domains from three strains. The cpe promoter region from one strain contained a 45-bp insertion compared with previously published sequences. This insertion was also found in two (of five) other Cpe+ strains. cpe gene expression in C. perfringens was measured by using translational fusions of each promoter type to the Escherichia coli gusA gene, which codes for beta-glucuronidase. For either promoter type, cpe-gusA expression was undetectable throughout exponential growth but increased dramatically at the beginning of the stationary phase. To measure cpe expression in Bacillus subtilis, cpe-gusA fusions were integrated into the B. subtilis chromosome. Both types of promoter exhibited moderate expression during exponential growth; cpe expression increased threefold at the beginning of the stationary phase. Transcriptional start sites were determined by primer extension and in vitro transcription assays. For C. perfringens, both types of promoter gave the same 5' end, 197 bp upstream of the translation start (50 bp downstream of the 45-bp insertion). In B. subtilis, however, the 5' end was internal to the 45-bp insertion, suggesting the use of a different promoter than that utilized by C. perfringens.

Proteolysis of Clostridium perfringens type A enterotoxin during purification

The small satellite bands of enterotoxin frequently seen in polyacrylamide gels following purification of Clostridium perfringens enterotoxin were found to be due to endogenous protease activity and were not present if phenylmethylsulfonyl fluoride (PMSF; 1 mM) and EDTA (10 mM) were used in the purification protocol. The use of PMSF was avoided by passing gel filtration-purified enterotoxin material through DEAE-Sephacel. This modified protocol resulted in an 11.4-fold purification of enterotoxin and a 26.8% yield. Contrary to previous reports (B. R. Dasgupta and M. W. Pariza, Infect. Immun. 38: 592-597, 1982), if PMSF and EDTA were included during purification, we were unable to detect the novel enterotoxin ET-1 produced by strain NCTC 10240. C. perfringens proteases cleaved homogeneous enterotoxin into two additional fragments, suggesting that ET-1 was a product of endogenous protease action during purification.

Toxigenic clostridia

Toxigenic clostridia belonging to 13 recognized species are discussed in this review. Each species or group of organisms is, in general, introduced by presenting the historical aspects of its discovery by early investigators of human and animal diseases. The diseases caused by each species or group are described and usually discussed in relation to the toxins involved in the pathology. Morphological and physiological characteristics of the organisms are described. Finally, the toxins produced by each organism are listed, with a presentation of their biological activities and physical and biochemical characteristics. The complete amino acid sequences for some are known, and some of the genes have been cloned. The term toxin is used loosely to include the various antigenic protein products of these organisms with biological and serological activities which have served as distinguishing characteristics for differentiation and classification. Some of these factors are not truly toxic and have no known role in pathogenicity. Some of the interesting factors common to more than one species or group are the following: neurotoxins, lethal toxins, lecithinases, oxygen-labile hemolysins, binary toxins, and ADP-ribosyltransferases. Problems in bacterial nomenclature and designation of biologically active factors are noted.

Evaluation of ELISA, RPLA, and Vero cell assays for detecting Clostridium perfringens enterotoxin in faecal specimens

Three hundred and ninety two faecal specimens from 70 separate outbreaks of suspected Clostridium perfringens food poisoning were examined by enzyme linked immunosorbent assay (ELISA), reversed passive latex agglutination (RPLA), and Vero cell assays for the presence of enterotoxin. Although the most time consuming method, ELISA was the most specific and reproducible. RPLA was slightly more sensitive than ELISA, but it showed some non-specific reactions. The Vero cell assay was the least sensitive and least reproducible method, being affected by some non-specific cytotoxic and cytotonic reactions. Normal rabbit serum should be included in the Vero cell assay as a control for the neutralisation of cytotoxic effects.

Characterization of an outbreak of Clostridium perfringens food poisoning by quantitative fecal culture and fecal enterotoxin measurement

Published criteria for implicating Clostridium perfringens as the cause of food-poisoning outbreaks include finding a median fecal C. perfringens spore count of greater than 10(6)/g among specimens from ill persons. We investigated a food-poisoning outbreak with the epidemiologic characteristics of C. perfringens-related disease in a nursing home in which the median fecal spore count for ill patients (2.5 X 10(7)/g) was similar to that for well patients (4.0 X 10(6)/g), making the etiology of the outbreak uncertain. All ill and well patients tested had eaten turkey, the implicated food item. C. perfringens enterotoxin was detected by reverse passive latex agglutination in fecal specimens from six of six ill and none of four well patients who had eaten turkey (P = 0.005), suggesting that this organism had caused the outbreak. This investigation suggests that detection of fecal C. perfringens enterotoxin is a specific way to identify this organism as the causative agent in food-poisoning outbreaks.

Response of ligated rabbit ileal loop to Clostridium perfringens type C strains and their toxic filtrates

The vegetative cells and toxic filtrates of Clostridium perfringens type C strains were injected into ligated rabbit ileal loops and the responses were observed. Out of 12 strains examined, 2 strains showed positive reaction in this test, when the vegetative cells were injected. One of these 2 strains was an enterotoxigenic and beta-toxigenic and the other was beta- and delta-toxigenic but not enterotoxigenic. Culture filtrates containing beta or delta toxin also showed fluid accumulation in the rabbit ileal loop. Histological findings of loops injected with culture filtrates containing beta toxin showed separated and effaced villi, hemorrhage in the mucosa, engorged vessels, inflammatory cell infiltration, and hyperplasia of the lymphoid tissue.

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.

A double antibody sandwich enzyme-immunoassay for Clostridium perfringens type A enterotoxin detection in stool specimens

A double antibody sandwich enzyme-immunoassay has been developed for detection of Clostridium perfringens enterotoxin. Anti-enterotoxin immunoglobulin G-alkaline phosphatase conjugates were prepared using a rapid minicolumn procedure. The assay can achieve a sensitivity of greater than or equal to 1 ng/ml with purified enterotoxin. Sensitivity for detection of cases of C. perfringens enteritis in a C. perfringens outbreak (86 individuals tested) was between 85.7 and 98.0 per cent depending upon stringency of criteria for defining positive cases. Specificity of the assay was demonstrated by the lack of positive results in 53 individuals involved in a gastroenteritis outbreak of unknown etiology.

Bacteroides fragilis: a possible cause of acute diarrheal disease in newborn lambs

Bacteroides fragilis with enterotoxin-like activity (BFEL) was isolated from the feces of 24- to 48-h-old lambs with acute diarrheal disease on three different sheep ranches in the Northern Rocky Mountain region of the United States. The lamb intestinal loop test was used to enrich for the bacterium before its initial isolation. Pure cultures of B. fragilis from the feces of diarrheic lambs caused fluid accumulation in five of five lamb intestinal loop tests and in three of three calf intestinal loop tests. Two different serogroups of BFEL were found in diarrheic lambs, and a third serogroups was found in the feces of a diarrheic ewe. Enteric disease characterized by diarrhea, depression, and inappetence occurred in three of eight newborn, colostrum-fed lambs after oral challenge inoculation with viable BFEL. One of the three lambs died 32 h after challenge. Clinical signs of disease were similar to those observed in the naturally occurring disease. B. fragilis is an obligately anaerobic bacterium found in the intestinal tract of most animals and humans. It is a serious cause of extraintestinal infection in humans. The bacterium has not been reported to cause fluid accumulation in the intestine or to cause diarrhea in any species of animal.

Isolation and some properties of an enterotoxin produced by Bacillus cereus

Extracellular proteins produced by Bacillus cereus B-4ac were separated by chromatography on Amberlite CG-400, QAE-Sephadex, Sephadex G-75, and hydroxylapatite. A fraction, containing three detectable antigens, obtained from chromatography on hydroxylapatite caused fluid accumulation in ligated rabbit ileal loops, was dermonecrotic to rabbit skin, was cytotoxic to cultured cells, and was lethal to mice after intravenous injection. Two other fractions obtained from chromatography on hydroxylapatite showed essentially no toxic activity when tested individually. Each nontoxic fraction contained two of the three proteins present in the toxic material. When the two nontoxic fractions were combined, activity in all of the biological assays was observed. Antiserum against either of the nontoxic fractions neutralized the dermonecrotic response of the combined material. These results suggest that all of these biological activities probably are due to a single entity and that more than one component probably comprise the toxic entity.

Relationship of sporulation, enterotoxin formation, and spoilage during growth of Clostridium perfringens type A in cooked chicken

Sporulation and enterotoxin formation were determined for 17 strains of Clostridium perfringens type A in autoclaved chicken dark meat and in Duncan-Strong sporulation medium. The mean numbers of heat-resistant spores detected after 24 h at 37 degrees C were log10 1.13 to log10 7.64/ml in Duncan-Strong medium and log10 4.93 to log10 6.59/g in chicken. Of 17 strains, 7 formed enterotoxin in Duncan-Strong culture supernatant (1.0 to 60 microgram/ml) and 8 produced enterotoxin in chicken (0.21 to 24 microgram/g). Additional studies with chicken were conducted with C. perfringens NCTC 8239. With an inoculum of 10(6) cells per g, greater than log10 7.99 vegetative cells per g were detected by 4 h in chicken at 37 degrees C. Heat-resistant spores occurred by 4 and 6 h and enterotoxin occurred by 8 and 6 h in autoclaved chicken dark meat and barbecued chicken drumsticks, respectively. Enterotoxin was detected in autoclaved dark meat after incubation at 45 degrees C for 1.5 h followed by 37 degrees C for 4.5 h, but not after incubation at 45 degrees C for 1.5 to 8 h. With an inoculum of 10(2) cells per g in oven-cooked or autoclaved chicken, greater than log10 8.00 vegetative cells per g were detected by 6 to 8 h at 37 degrees C, heat-resistant spores were detected by 8 h, and enterotoxin was detected by 12 h. A statistical analysis of odor determinants of chicken after growth of C. perfringens indicated that, at the 95% confidence level, the product was considered spoiled (off or unwholesome odor) by the time spores or enterotoxin were formed.

Highly sensitive assay for Clostridium perfringens enterotoxin that uses inhibition of plating efficiency of Vero cells grown in culture

A highly sensitive and reproducible biological assay for Clostridium perfringens enterotoxin is described that uses Vero (African green monkey kidney) cells grown in tissue cultures. Very small doses of the enterotoxin inhibited the plating efficiency of the cells. This inhibition of plating efficiency could be used to detect as little as 0.1 ng (1 ng/ml) of enterotoxin, and a linear dose-response curve was obtained with 0.5 to 5 ng (5 to 50 ng/ml). A nonlinear, but reproducible, curve was obtained with a dose range from 0.1 to 100 ng (1 to 1,000 ng/ml). A new unit of biological activity, called the plating efficiency unit, was defined as that amount of enterotoxin that caused a 25% inhibition of the plating of 200 cells inoculated into 100 microliters of medium in a microwell culture system. One milligram of highly purified enterotoxin contained about 400,000 plating efficiency units. Additional studies demonstrated that the biological and serological activities of the enterotoxin molecule were not equally labile.

Effects of pH shifts, bile salts, and glucose on sporulation of Clostridium perfringens NCTC 8798

The sporulation of Clostridium perfringens NCTC 8798 was studied after exposing vegetative cells to: pH values of 1.5 to 8.0 in fluid thioglycolate broth (for 2h) and then transferring them to Duncan-Strong (DS) sporulation medium; sodium cholate or sodium deoxycholate (0.3 to 6.5 mM) in DS medium; or Rhia-Solberg medium with 0.4% (wt/wt) starch, glucose, or both added at 0 to 55 mM. At pH 1.5, no culturable heat-resistant spores were formed. For cells exposed to pH 3.0, 4.0, 5.0, or 6.0, increases in heat-resistant spores were not seen until after a lag of 12 to 13 h, whereas the lag was only 2 to 3 h for cells exposed to pH 7.0 or 8.0. Maximal spore crops were produced after only 6 to 8 h for cells exposed to pH 7 or 8, but 16 to 18 h was required for production of maximal spore crops by cells exposed to the lower-pH media. The addition of sodium cholate (3.5 to 6.5 mM) to DS medium only slightly reduced the culturable heat-resistant spore count from 1.9 X 10(7) to 3 X 10(6)/ml. The addition of 1.8 mM or more sodium deoxycholate reduced the culturable heat-resistant spore count to less than 10/ ml. When either starch or glucose alone was added to Rhia-Solberg medium there was no production of culturable heat-resistant spores, but a combination of 0.4% (wt/wt) starch and 4.4 mM glucose yielded 6 X 10(5) spores/ml. The spore production remained at this level for glucose concentrations of 6 to 22 mM, but then declined to about 3 X 10(3) spores per ml at higher concentrations.

Enterotoxins from gram-negative bacteria relevant for veterinary medicine

The chemistry, mechanism of action, assay methods, pharmacology, and prevention and treatment of diarrhoea due to toxins of gram-negative microbes are discussed. Other virulence factors are mentioned briefly. Special emphasis is placed on non-specific treatment by oral rehydration.

Clostridium perfringens in animal disease: a review of current knowledge

The diseases caused by various types of Clostridium perfringens are critically reviewed in the light of current knowledge. Particular emphasis is placed on information concerning these diseases in Canadian livestock. There are two etiologically clearly-defined acute C. perfringens diseases recognized in Canada: hemorrhagic enteritis of the new born calf, caused by C. perfringens type C, and enterotoxemia of sheep, caused by type D. Clostridium perfringens type A may play a role as a secondary pathological agent in various disease conditions, such as necrotic enteritis of chickens. It may also cause wound infections and may provide a source for human food poisoning outbreaks. There appears to be a considerable lack of knowledge regarding the distribution of C. perfringens types, their pathogenesis, diagnosis and the incidence of diseases caused by this organism.

Detection of Clostridium perfringens enterotoxin in human fecal samples and anti-enterotoxin in sera

By using counterimmunoelectrophoresis (CIEP), Clostridium perfringens enterotoxin was successfully demonstrated in fecal samples collected within 1 day of attack from sick individuals involved in a bacteriologically and epidemiologically proven outbreak of C. perfringens food poisoning. In contrast, enterotoxin was not demonstrable in fecal samples of apparently healthy individuals both at high- and low-risk exposure to the organism and enterotoxin or in fecal samples collected 4 to 5 days after a food poisoning outbreak. A 100% prevalence of C. perfringens anti-enterotoxin in sera of human volunteers at high- as well as low-risk exposure to the organism and enterotoxin was recorded with CIEP.