Rapid death of infant rhesus monkeys injected with Clostridium difficile toxins A and B: physiologic and pathologic basis

Are Clostridium difficile toxins nephrotoxic?

Clostridium difficile-associated disease (CDAD) occurs along a spectrum from simple uncomplicated enteritis to a multi-system disease which may include nephropathy. Pathology is attributed to bacterial toxins, but it is unclear if the latter are directly nephrotoxic. Anecdotes of renal disease from human biopsy findings suggest a variation of histopathologies, but data are relatively limited. Acute renal failure does occur in patients with advanced morbidity. CDAD can complicate chronic renal failure. Kidney tissue culture cytotoxicity has long been known. Kidney function alterations among animal models or diseased humans are relatively uncommon in mild to moderate enteritis. Rare findings of toxinemia are reported. Some have proposed that renal dysfunction arises more from pre-renal compromises. Direct toxin studies on whole kidney are sparse. The role of direct toxin-associated renal disease is worthy of further investigation given the current impetus towards the development of protective and therapeutic passive and active immunity. Hypotheses of toxin-direct or pre-renal toxin compromise of renal function prevail.

The Comparative Pathology of Clostridium difficile-associated Disease

Clostridium difficile is a confirmed pathogen in a wide variety of mammals, but the incidence of disease varies greatly in relation to host species, age, environmental density of spores, administration of antibiotics, and possibly, other factors. Lesions vary as well, in severity and distribution within individuals, and in some instances, age groups, of a given species. The cecum and colon are principally affected in most species, but foals and rabbits develop severe jejunal lesions. Explanations for variable susceptibility of species, and age groups within a species, are largely speculative. Differences in colonization rates and toxin-receptor densities have been proposed. Clostridium difficile-associated disease is most commonly diagnosed in Syrian hamsters, horses, and neonatal pigs, but it is reported sporadically in many other species. The essential virulence factors of C. difficile are large exotoxins, toxin A (TcdA) and toxin B (TcdB). Receptor-mediated endocytosis of the toxins is followed by endosomal acidification, a necessary step for conversion of the toxin to its active form in the cytosol. Cell-surface receptors have been characterized for TcdA, but remain to be identified for TcdB. Both TcdA and TcdB disrupt the actin cytoskeleton by disrupting Rho-subtype, intracellular signaling molecules. Disruption of the actin cytoskeleton is catastrophic for cellular function, but inflammation and neurogenic stimuli are also involved in the pathogenesis of the disease.

The Distribution and Density of Clostridium difficile Toxin Receptors on the Intestinal Mucosa of Neonatal Pigs

Clostridium difficile is an enteric pathogen affecting a variety of mammals, but it has only recently been diagnosed as a cause of neonatal typhlocolitis in pigs. The most important virulence factors of C. difficile are 2 large exotoxins, toxin A (TcdA) and toxin B (TcdB). TcdA is a potent enterotoxin with effects on host tissues that are dependent upon receptor-mediated endocytosis of the intact toxin. TcdB is an effective cytotoxin, but it apparently does not bind receptors on intact mucosal epithelium. TcdB is much less toxic in vivo unless there is underlying damage to the mucosa, and it is not essential for the virulence of C. difficile. One hypothesis to explain the resistance of most species as neonates (e.g., humans and hamsters) is that they may lack significant numbers of TcdA receptors. The susceptibility of neonatal pigs suggests cells of the gastrointestinal mucosa express sufficient numbers of toxin receptors for lesion development. Immunohistochemical (IHC) assays documented specific binding of TcdA, but not TcdB, to the epithelium of the small and large intestine. The carbohydrate Galα1–3/β1–4GlcNAc-R has been described as an important receptor for TcdA. However, IHC indicated a distribution on cell surfaces much different from that of TcdA binding, suggesting a specific interaction of toxin with an alternative receptor.

Immunization strategies for Clostridium difficile infections

Clostridium difficile infection is a major cause of nosocomial disease in Western countries. The recent emergence of hypervirulent strains resistant to most antibiotics correlates with increasing disease incidence, severity and lethal outcomes. Current treatments rely on metronidazol and vancomycin, but the limited ability of these antibiotics to cure infection and prevent relapse highlights the need for new strategies. A better knowledge of the molecular mechanisms of the disease, the host immune response and identification of key virulence factors of Clostridium difficile now permits the development of new products specifically targeting the pathogen. Immune-based strategies relying on active vaccination or passive administration of antibody products are the focus of intense research and, today, the efficacy of monoclonal antibodies and of two vaccines are evaluated clinically. This review presents recent data, discusses the different strategies and highlights the challenges linked to the development of immunization strategies against this emerging threat.

Models for the study of Clostridium difficile infection

Models of Clostridium difficile infection (C. difficile) have been used extensively for Clostridium difficile (C. difficile) research. The hamster model of C. difficile infection has been most extensively employed for the study of C. difficile and this has been used in many different areas of research, including the induction of C. difficile, the testing of new treatments, population dynamics and characterization of virulence. Investigations using in vitro models for C. difficile introduced the concept of colonization resistance, evaluated the role of antibiotics in C. difficile development, explored population dynamics and have been useful in the evaluation of C. difficile treatments. Experiments using models have major advantages over clinical studies and have been indispensible in furthering C. difficile research. It is important for future study programs to carefully consider the approach to use and therefore be better placed to inform the design and interpretation of clinical studies.

Translocation of Clostridium difficile toxin B across polarized Caco-2 cell monolayers is enhanced by toxin A

Clostridium difficile is the etiological agent of antibiotic-associated diarrhea; the most common form of nosocomial infectious diarrhea. The basis for the shock-like systemic symptoms observed in severe cases of this infection are not known. It is hypothesized that the invasion of C difficile toxins A and/or B from the gut mucosa may contribute to these symptoms.A polarized tissue culture model employing Caco-2 cells grown on transwell inserts was established to study the translocation of purified C difficile toxins A and B. C difficile toxins were (125)I labelled and inoculated onto confluent polarized Caco-2 cell monolayers to study translocation dynamics. Electrical resistance measurements were used to monitor monolayer confluence and tight junction integrity. Samples were taken from the apical and basal sides of the insert, as well as the insert itself, and tested using the human foreskin fibroblasts cell cytotoxicity assay to monitor partitioning of the radiolabelled toxins. Toxin A produced a 50% reduction in electrical resistance in 3 h whereas the same concentration of toxin B required at least 7 h to achieve the same effect. Both toxins A and B were able to translocate across confluent monolayers of Caco-2 cells. The combination of toxin A and B together was synergistic with respect to promoting the translocation of toxin B. Although the addition of toxin A resulted in a 100% increase in the amount of toxin B able to translocate, no increases in toxin A translocation were observed. These findings suggest a model of pathogenesis in which C difficile toxin A facilitates the translocation of toxin B from the gut into submucosal areas where it may play a role in inflammatory damage.

Leukemoid Reactions Complicating Colitis due to Clostridium difficile

BACKGROUND

We sought to describe the characteristics of patients who had Clostridium difficile colitis complicated by leukemoid reactions (total leukocyte count greater than 35 x 10(9)/L) and to determine whether this complication is associated with higher morbidity or mortality than C difficile colitis without leukemoid reactions.

METHODS

We performed a retrospective case series analysis of patients with a positive fecal assay for C difficile toxin and a peak leukocyte count greater than 35 x 10(9)/L during 1998 and 1999. Twenty cases that met these criteria were compared with 65 randomly selected control patients (patients with a positive C difficile toxin and a peak leukocyte count less than 35 x 10(9)/L).

RESULTS

The mean peak leukocyte count was 52 +/- 18.2 x 10(9)/L (+/- SD) in the case group and 14.9 +/- 6.5 x 10(9)/L in the control group. Patients with a leukemoid reaction had a lower temperature, a lower serum albumin level, and a higher hematocrit value. Multivariable logistic regression showed respiratory tract infection and lower temperature to be independent predictors of a leukemoid reaction. There were 10 deaths (50%) in the leukemoid reaction group and 5 deaths (7.7%) in the control group. All seven patients with a peak leukocyte count greater than 50 x 10(9)/L died, compared with eight deaths (10.3%) among the remaining 78 patients whose peak leukocyte count was less than 50 X 10(9)/L.

CONCLUSION

Patients with C difficile colitis and a leukocyte count greater than 35 x 10(9)/L have a poor prognosis with a much higher mortality rate than patients who have C difficile colitis without a leukemoid reaction.

A primer of primate pathology: lesions and nonlesions

Nonhuman primates are important laboratory animals for biomedical, pharmacology, and toxicology research. To effectively use primates as models, their gross and histologic anatomy, physiology and natural history, as well as common health problems and the source from which the primate is obtained, must be known and understood by pathologists involved in study design and/or interpretation. The first very important lesson in the "primer" is: there is no such thing as a generic monkey. Brand names (ie, species and subspecies) are important. Several taxonomic groups of primates are used in research including: prosimians, such as galagos and lemurs; New World monkeys, particularily marmosets; Old World monkeys, especially macaques and baboons; and the chimpanzee, an African ape. Differences between taxa are exemplified by the glucocorticoid resistance of New World monkeys compared to Old World monkeys, which results in the requirement for Vitamin D3 and their high circulating levels of steroids such as cortisone and progesterone. Differences in ovarian histology between Old and New World monkeys probably relate to steroid receptor biology as well. There are also variations in disease manifestations, even among closely related primate species such as rhesus and cynomolgus macaques (cynos). For example type D retrovirus infection is accompanied by lymphomas in cynos, but not rhesus. The second important lesson in this "primer" is: "not test article related" does not always mean "normal." Lymphoid nodules in bone marrow or salivary gland, a common background finding in macaques, often signal the presence of type D retrovirus. Other histologic changes and normal anatomic variations may be confusing to individuals not routinely examining primate tissues. The objective of this paper is to familiarize pathologists with the use of primates in research as well as lesions and nonlesions (normal anatomy or physiology) of primates that may influence study design and confound interpretation.

Effects of Clostridium difficile toxins on epithelial cell barrier

Clostridium difficile is the primary agent responsible for many patients with antibiotic-associated diarrhea and almost all patients with pseudomembranous colitis following antibiotic therapy. C. difficile infection is the most frequent form of colitis in hospitals and nursing homes and affects millions of patients in the United States and abroad. The first event in the pathogenesis of C. difficile infection involves alterations of the indigenous colonic microflora by antibiotics, followed by colonization with C. difficile. C. difficile causes diarrhea and colitis by releasing two high molecular weight protein exotoxins, toxin A and toxin B, with potent cytotoxic and enterotoxic properties. Evidence presented here indicates that C. difficile toxins compromise the epithelial cell barrier by at least two pathophysiologic pathways, one involving disaggregation of actin microfilaments in colonocytes via glucosylation of the Rho family of proteins leading to epithelial cell destruction and opening of the tight junctions, whereas the other appears to involve early release of proinflammatory cytokines from intestinal epithelial cells probably via activation of MAP kinases. We speculate that cytokines released from intestinal epithelial cells in response to toxin A exposure will diffuse into the lamina propria and activate macrophages, enteric nerves, and sensory neurons to release SP, CGRP, and NT, which, in turn, interact with immune and inflammatory cells and amplify the inflammatory response. Dissection of this inflammatory cascade may help us understand the pathophysiology of inflammatory diarrhea caused by this important pathogen.

Immunological evidence for a bacterial toxin aetiology in sudden infant death syndrome

Toxin-specific antibodies to clostridial, enterobacterial and staphylococcal toxins implicated in sudden infant death syndrome were studied in sera from sudden infant death syndrome infants and a comparison group of infants (babies with phenylketonuria). The results indicated a higher proportion of sera from sudden infant death syndrome infants contained IgA that bound to clostridial and enterobacterial toxins but a higher proportion of sera from the phenylketonuria comparison group contained IgA that bound staphylococcal toxins. The higher proportion of serum samples with IgG and IgM in the healthy comparison babies serum probably indicated immunity in this group of babies to these toxins. The effect of gender and age had a minimal effect on the incidence of these antibodies. The presence of toxin-specific antibodies in sudden infant death syndrome and the of comparison infants suggests that all infants are exposed to these toxins and most babies successfully overcome the toxic challenge. Some infants with predisposing risk factors (temperature change, smoking, infection, immune development, sleeping position, etc.) that could affect the baby's immune competency could succumb to these and possibly other toxins. This immunological evidence further strengthens the view that bacterial toxins are a significant cause of sudden infant death syndrome.

Serum antitoxin antibodies mediate systemic and mucosal protection from Clostridium difficile disease in hamsters

Clostridium difficile is the bacterial pathogen identified as the cause of pseudomembranous colitis and is principally responsible for nosocomial antibiotic-associated diarrhea and colitis. The pathologic findings associated with this infection are believed to be caused by two large (approximately 300-kDa) exotoxins, toxins A and B. Because of the mucosal nature of this infection, vaccination strategies aimed at providing prophylactic or therapeutic immune protection have included immunization by mucosal routes. Using the hamster model of C. difficile infection, we examined the protective efficacy of inactivated toxin (toxoid) vaccine formulations prepared as either culture filtrate or partially purified toxoid. We compared combination parenteral and mucosal vaccination regimens involving intranasal, intragastric, or rectal routes of immunization and found that rectal immunization in conjunction with intramuscular (i.m.) vaccination provided full protection of hamsters from death and diarrhea while the other mucosal routes did not. Protection was associated with high levels of toxin-neutralizing antibodies in serum. The requirement for adjuvants for protection was assessed by using sequential i.m. and rectal or i.m. vaccination regimens. Unexpectedly, i.m. immunization without adjuvant conferred the highest protection from death and diarrhea; this regimen elicited the highest serum anti-toxin B titers as well as toxin B neutralizing titers. Passive transfer of mouse antitoxin antibodies protected hamsters in a dose-dependent manner, demonstrating the principal role of circulating antitoxin antibodies in immunity from this toxin-mediated mucosal disease. These results suggest that prophylactic parenteral vaccination or intravenous immunotherapy could provide protection from C. difficile disease in humans.

Human disease associated with Clostridium perfringens enterotoxin

Clostridium perfringens continues to be a common cause of food-borne disease. Characteristics of this organism that contribute to its ability to cause food-borne illness include the formation of heat-resistant spores that survive normal cooking/heating temperatures, a rapid growth rate in warm food, and the production of enterotoxin (CPE) in the human gut. Time and temperature abuse associated with food preparation contributes to the majority of outbreaks of C. perfringens food-borne disease. CPE-induced diarrhea has been reported in the absence of a defined food vehicle. These cases have been typically associated with the elderly and following a course of antibiotic therapy. The incidence of CPE-induced diarrhea may be expected to increase with the growing population of immunocompromised (disease-, treatment-, or age-induced) individuals. Clostridium perfringens has been implicated as a possible contributor to the development of SIDS in susceptible individuals. Specifically, it has been hypothesized that CPE acts as a triggering agent, initiating the events associated with the development of SIDS. Continued refinement of both immunoassays and molecular methods for toxin and gene detection, respectively, will facilitate their eventual availability as commercial kits, providing rapid and simplified methods for the detection of C. perfringens isolates that produce or have the capacity to produce CPE as well as other toxins associated with this organism.

Clostridium perfringens type A enterotoxin (CPE): more than just explosive diarrhea

The bacterial pathogen Clostridium perfringens is the most prolific toxin-producing species within the clostridial group. The toxins are responsible for a wide variety of human and veterinary diseases, many of which are lethal. C. perfringens type A strains are also associated with one of the most common forms of food-borne illness (FBI). The toxicosis results from the production and gastrointestinal absorption of a protein-enterotoxin known as CPE. The regulation, expression, and mechanism of action of CPE has been of considerable interest as the protein is unique. CPE expression is sporulation associated, although the mechanism of cpe-gene regulation is not fully elucidated. Cloning studies suggest the involvement of global regulators, but these have not been identified. Although very few type A strains are naturally enterotoxigenic, the cpe gene appears highly conserved. In FBI strains, cpe is chromosomally encoded; whereas in veterinary strains, cpe may be plasmid-encoded. Variation in cpe location suggests the involvement of transposable genetic element(s). CPE-like proteins are produced by some C. perfringens types C and D; and silent remnants of the cpe gene can be found in C. perfringens type E strains associated with the iota toxin gene. CPE has received attention for its biomedical importance. The toxin has been implicated in sudden infant death syndrome (SIDS) because of its superantigenic nature. CPE can destroy a wide variety of cell types both in vitro and in vivo, suggesting that it could have potential in the construction of immunotoxins to neoplastic cells. It is obvious that CPE is an interesting protein that deserves continued attention.

The low molecular mass GTP-binding protein Rho is affected by toxin A from Clostridium difficile

Enterotoxin A is one of the major virulence factors of Clostridium difficile, and the causative agent of antibiotic-associated pseudomembranous colitis. In cell culture (NIH-3T3, rat basophilic leukemia cells) toxin A inhibits Clostridium botulinum ADP-ribosyltransferase C3 (C3)-catalyzed ADP-ribosylation of the low molecular mass GTP-binding Rho proteins. Rho participates in the regulation of the microfilament cytoskeleton. Decrease in ADP-ribosylation of Rho occurs in a time- and concentration-dependent manner and precedes the toxin A-induced destruction of the actin cytoskeleton. Action of toxin A is not due to proteolytical degradation of Rho or to an inherent ADP-ribosyltransferase activity of toxin A. Toxin A-induced decrease in ADP-ribosylation is observed also in cell lysates and with recombinant RhoA protein. A heat stable low molecular mass cytosolic factor is essential for the toxin effect on Rho. Thus, the enterotoxin (toxin A) resembles the effects of the C. difficile cytotoxin (toxin B) on Rho proteins (Just, I., G. Fritz, K. Aktories, M. Giry, M. R. Popoff, P. Boquet, S. Hegenbath, and C. Von Eichel-Streiber. 1994. J. Biol. Chem. 269:10706-10712). The data indicate that despite different in vivo effects, toxin A and toxin B act on the same cellular target protein Rho to elicit their toxic effects.

Clostridium difficile toxin A therapy for HCT 116 human colon cancer in nude mice

Clostridium difficile toxin A was evaluated for an antitumor effect in vivo on HCT 116 human colon carcinoma cells growing subcutaneously in nude mice. A mean reduction in tumor volume of at least 65%, by measurement in three dimensions, was observed in mice who received two 9- to 13-day courses of daily intraperitoneal injections of toxin A as compared to mice receiving diluent alone. Reversible adverse effects of toxin A were noted in some animals, consisting primarily of liver toxicity and skin rash. HCT 116 cells in toxin A-treated mice grew as flattened tumors with ulcerated centers compared to rounded tumors without ulceration in controls. Histologic examination of tumors from representative mice revealed that two thirds of the tumor in a treated mouse was necrotic compared to only one third in a control, suggesting greater antitumor efficacy of toxin A than estimated by tumor measurements alone.

The role of infectious agents in sudden infant death syndrome

Epidemiological factors associated with susceptibility to respiratory infections are similar to those associated with Sudden Infant Death Syndrome. Here we review the evidence that respiratory pathogens might be involved in some cases of Sudden Infant Death Syndrome in the context of factors identified in epidemiological studies of cot deaths: the age range affected; mother' smoking; respiratory viral infections; immunisation status. Both laboratory and epidemiological evidence suggests that vulnerability of infants to infectious agents depends on interactions between genetic, developmental and environmental factors that contribute to colonisation by microorganisms, the inflammatory and specific immune responses and the infants' physiological responses to inflammatory mediators. A model is proposed to explain how microorganisms might trigger a series of events resulting in some of these unexpected deaths and discusses how the the present recommendations regarding child care practices might help reduce the numbers of Sudden Infant Death Syndrome cases associated with infectious agents.

Can superantigens trigger sudden infant death?

A majority of sudden infant death syndrome (SIDS) victims have respiratory or gastrointestinal infections prior to death. This has led to an investigation of the role of pathogenic bacteria and the potentially lethal toxins they produce as triggers for sudden infant death. A small group of bacteria have been consistently identified in SIDS victims as compared to controls, and remarkably, three of these produce superantigenic toxins. Superantigens exert a powerful effect on the immune system, stimulating T-cells, which subsequently induces the formation of large amounts of cytokines. Generation of an overwhelming inflammatory response may lead to death by shock, or other, as yet unrecognized effects of the toxin on the respiratory or cardiac systems. A SIDS/superantigen model is proposed which may explain many of the pathological characteristics of SIDS and establish quantifiable markers for SIDS.

Sudden infant death syndrome (SIDS): are common bacterial toxins responsible, and do they have a vaccine potential?

Despite extensive research, no unifying concept has satisfactorily explained the cause of the sudden infant death syndrome (SIDS). The details are briefly outlined of some of the evidence supporting the hypothesis that common bacterial toxins are important in the aetiology of SIDS. These bacterial toxins act as triggers to initiate a biochemical cascade resulting in death. Data from four research groups, each working independently, indicated that the bacteria Clostridium perfringens, Escherichia coli, Staphylococcus aureus, Streptococcus spp. and Enterococcus spp. were present in higher numbers in infants who had suffered SIDS than in control infants. Certainly more detailed studies need to be performed on the role of bacterial infections in infants. There are many implications arising from this work, particularly the use of vaccination as a means of reducing infections, and consequently the number of SIDS deaths.

The potential role of bacterial toxins in sudden infant death syndrome (SIDS)

Toxigenic bacteria have been implicated in some cases of Sudden Infant Death Syndrome (SIDS). Although there is not much evidence that Clostridia spp. are associated with SIDS in Britain, strains of Staphylococcus aureus producing pyrogenic toxins have been isolated from significant numbers of these infants at autopsy The pyrogenic toxins, produced by some strains of group A Streptococcus pyogenes as well as staphylococci, are powerful "superantigens" that have significant physiological effects including induction of fever > 38 degrees C. In this article, interactions between genetic and environmental factors that might enhance colonization of epithelial surfaces by toxigenic staphylococci are analyzed: infant's expression of Lewis(a) antigen which acts as a receptor for some microorganisms; viral infections; the effect of mother's smoking on susceptibility to respiratory infection. Based on epidemiological findings and laboratory investigations, a hypothesis is proposed to explain how bacteria producing pyrogenic toxins might contribute to some cot deaths.

Postantibiotic colonization with Clostridium difficile in nursing home patients

Clostridium difficile causes pseudomembranous colitis and is responsible for 20% to 25% of cases of postantibiotic diarrhea. In an earlier study, nursing-home patients with C. difficile infection were noted to have a high mortality rate. Because most of these infected patients had been treated with antibiotics, it was not clear whether this high mortality rate was associated with C. difficile infection or simply with antibiotic treatment. A prospective study was carried out to determine the rate of postantibiotic C. difficile colonization and risk factors for infection in patients in a 233-bed long-term care facility, as well as to determine whether C. difficile infection is associated with increased mortality. During a six-month period 150 courses of antibiotics were prescribed for 108 patients. Stool specimens were collected from 36 (33%) patients following the first course of antibiotic treatment, and 12 (33%) were infected with C. difficile. Risk factors for infection included ward location and stool incontinence. Age, body-mass index less than or equal to 18 kg/m2, and diagnoses of dementia and pressure scores tended to be associated with infection, but not significantly. Early mortality rates did not differ, but 12-month mortality for the infected patients was higher (83% vs 50%, P = .05). Therefore, we conclude that postantibiotic C. difficile infection serves as a marker of death in nursing-home patients, one that can be differentiated from the risk of antibiotic treatment alone. This increased death rate may be related in part to clinically unrecognized pseudomembranous colitis or, alternatively, to absorption of C. difficile toxins or even endotoxin from the gut lumen into the systemic circulation.

Maternal deaths associated with Clostridium sordellii infection

Clostridium sordellii is a common soil and enteric bacterium that is infrequently recovered from the vagina. We describe three women in which C. sordellii caused puerperal infection and a distinctive and lethal toxic shock-like syndrome. Patients were less than 1 week post partum and each had a single, limited focus of infection including infection associated with a retained vaginal sponge, a cesarean section operative site, and endometritis. Each patient had a distinctive course characterized by sudden onset of clinical shock marked by severe and unrelenting hypotension associated with marked, generalized tissue edema and "third spacing" with increased hematocrit, presence of marked leukemoid reaction with total neutrophil counts of 84,000/mm3, 66,000/mm3, and 93,600/mm3, absence of rash or fever, limited or no myonecrosis, and a rapid and uniformly lethal course. Hypoalbuminemia was also noted. Similar findings were noted in prior isolated reports of C. sordellii-mediated postpartum or surgical infection. Treatment of animals with C. sordellii or closely related C. difficile toxins produces similar findings. We suggest that localized infection with toxin-producing strains of C. sordellii can produce a rapidly lethal toxic shock-like syndrome. Further study and earlier recognition of this syndrome may be life-saving in other patients.

Toxin A from Clostridium difficile binds to rabbit erythrocyte glycolipids with terminal Gal alpha 1-3Gal beta 1-4GlcNAc sequences

The binding of Toxin A isolated from Clostridium difficile to rabbit erythrocyte glycolipids has been studied. Total lipid extracts from rabbit erythrocytes were subjected to thin-layer chromatography and toxin-binding glycolipids detected by using 125I-labeled Toxin A in a direct binding overlay technique. Two major and several minor toxin-binding glycolipids were detected in rabbit erythrocytes by this method. The results of structural analyses of the major toxin-binding glycolipids were consistent with a pentasaccharide-ceramide (Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer) and a branched decasaccharide-ceramide (Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-3[Gal alpha 1-3Gal beta 1-4GlcNAc beta 1-6]Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc-Cer) previously identified as the two most abundant glycolipids in rabbit erythrocytes. 125I-Toxin A binding to these glycolipids could be inhibited by bovine thyroglobulin, monospecific antiserum to the toxin, or by treatment of the glycolipids with alpha-galactosidase. The absence of toxin interaction with isoglobotriaosylceramide (Gal alpha 1-3Gal beta 1-4Glc-Cer) isolated from canine intestine suggested that the GlcNAc residue present in the terminal Gal alpha 1-3Gal beta 1-4GLcNAc sequence common to all known toxin binding glycoconjugates is required for carbohydrate-specific recognition by Toxin A. These observations are consistent with the proposed carbohydrate binding specificity of Toxin A for the nonreducing terminal sequence, Gal alpha 1-3Gal beta 1-4GlcNAc.

Ability of two Clostridium difficile strains from man and hare to produce cytotoxin in vitro and in gnotobiotic rodent intestines

Cytotoxin production by human (VP1) and hare (FD) strains of Clostridium difficile were compared both in vitro in a broth culture and in vivo in intestinal contents of gnotobiotic rodents. Strain VP1 produced about 1,000 times more cytotoxin than the FD strain, both in vitro and in vivo, although the population levels of the two strains were not significantly different either in vitro or in vivo. Ninety percent of gnotobiotic rats and 100% of gnotobiotic mice established with the VP1 strain died within 3 days, whereas no mortality in rats or mice was observed with the FD strain. The cytotoxin titre increased during the 3 weeks following establishment of the FD strain in mice, decreasing thereafter. Mice previously established with the FD strain were protected from VP1 strain challenge. Cytotoxin production was greatly decreased in diassociated mice, although the population levels of the two strains did not differ to a great extent.

Effect of toxin A and B of Clostridium difficile on rabbit ileum and colon

The effect of purified toxin A and partially purified toxin B on rabbit ileum and colon was investigated. Toxin A caused tissue damage which was followed by permeability changes and fluid accumulation in both tissues. Toxin A did not increase the permeability of the colon to the extent observed for ileum; secreted fluid contained less protein of plasma origin. Toxin B had no effect on either tissue. Secretory and tissue damaging properties of crude C difficile toxins were found to be due to toxin A.

Continuous microbiological and pathological study of 70 sudden and unexpected infant deaths: toxigenic intestinal clostridium botulinum infection in 9 cases of sudden infant death syndrome

As part of a programme to exclude infection as the cause of death in infants who died suddenly and unexpectedly necropsies were carried out on 70 such infants. In 11 cases (15%), a pathological diagnosis could be made at necropsy; in 9 of these, causative bacteria or viruses were found. The 59 cases in which the cause of death could not be found had histological features characteristic of sudden infant death syndrome (SIDS). Botulinum toxin was found in 9 SIDS cases (15%). 8 of these infants had botulinum toxin and organisms of different types (A, B, C, F, G) in the contents of the ileojejunum or colon. 4 of them also had toxin in the serum. No botulinum toxin or organisms were found in the 11 infants who died of identified causes or 18 other infants who died in hospital of known causes.