Clostridium difficile: its disease and toxins

Comparison of two commercial enzyme immunoassays with cytotoxicity assay and culture for the diagnosis of Clostridium difficile related diarrhea

184 stool samples were analysed for the presence of Clostridium difficile and toxins using the Meridian Premier Toxin A and TechLab Tox-A EIA kits, selective culture and cytotoxin assay. Of the 184 samples 36 stools tested positive for cytotoxin. In comparison the sensitivity and specificity of the EIAs and culture were as follows: Meridian, 72 and 87, TechLab, 64 and 95, and selective culture, 83 and 96%, respectively. The positive predictive values and negative predictive values for the various methods were: Meridian, 58 and 93, TechLab, 77 and 92, and selective culture, 83 and 96%, respectively. Discrepant results to those obtained by cytotoxicity assay were encountered with both EIA kits evaluated and less so by culture. In this study direct isolation of Clostridium difficile from stool samples most closely paralleled the findings of the "gold standard" cell line cytotoxicity assay. It appears that a single test for the determination of Clostridium difficile disease is adequate, although a second method improves the predictability of the diagnosis. Direct culture of feces provided a reliable secondary procedure to cytotoxicity assay. The EIAs were simple to use, labour efficient and provided a rapid result. However the lack of sensitivity and relative expense did not justify their routine use in our laboratory.

Comparison of PCR-based approaches to molecular epidemiologic analysis of Clostridium difficile

Representative isolates of the 10 serogroups of Clostridium difficile and 39 clinical isolates (30 toxigenic and 9 nontoxigenic), including 5 isolates from a confirmed nosocomial outbreak, were analyzed by using two previously described arbitrary-primer PCR (AP-PCR) molecular typing methodologies (AP-PG05 and AP-ARB11) and PCR ribotyping. The two AP-PCR methods investigated gave comparable results; AP-PG05 and AP-ARB11 identified 8 and 7 groups among the serogroup isolates and classified the clinical isolates into 21 and 20 distinct groups, respectively. PCR ribotyping also identified 8 unique groups among the serogroup isolates but classified the clinical isolates into 23 groups. In addition, when results obtained by the PCR methods were compared with typing data generated by pulsed-field gel electrophoresis (PFGE), PCR ribotyping and PFGE were found to be in agreement for 83% (29 of 35) of isolates typeable by both techniques while AP-PG05 was in agreement with PFGE for 60% (20 of 33) and AP-ARB11 was in agreement with PFGE for only 44% (17 of 36). These results indicate that PCR ribotyping is a more discriminatory approach than AP-PCR for typing C. difficile and, furthermore, that this technique generates results that are in higher concordance with those obtained by using an established method for differentiating isolates of this organism on a molecular level than are results generated by using AP-PCR.

Clinical prediction rules to optimize cytotoxin testing for Clostridium difficile in hospitalized patients with diarrhea

BACKGROUND

Although routine testing of hospitalized patients with diarrhea for Clostridium difficile cytotoxin has been advocated as a high-yield procedure, the rationale for this practice has been questioned. To target a low-yield subgroup for whom routine testing could be deferred, we derived a clinical decision rule for predicting results of the C difficile cytotoxin assay in hospitalized adults with diarrhea.

METHODS

We hypothesized a priori that two variables, antibiotic use (within 30 days prior to testing) and history of significant diarrhea (new onset of > 3 partially formed or watery stools per 24 hour period), would be highly predictive of cytotoxin results, and obtained these data on 480 consecutive patients who underwent diagnostic testing for C difficile at a university hospital and affiliated Veterans Affairs medical center. For more detailed modelling, we recorded symptoms, signs, comorbidity, and other potential causes of diarrhea for 68 test positive patients (cases) and 265 randomly selected test negative patients (controls) within the study cohort.

RESULTS

The overall prevalence of positive cytotoxin assays was 14%. Prior antibiotic therapy (OR = 9.0, 95% CI 2.1-38.4), significant diarrhea (OR = 2.2, 95% CI 1.1-4.7), and abdominal pain (OR = 1.9, 95% CI 0.96-3.7) were independent predictors of cytotoxin assay results. The model discriminated patients with positive and negative assays with a receiver operating characteristic (ROC) area of 0.68; observed and predicted probabilities of a positive cytotoxin assay were well correlated over the entire range of observed probabilities (r2 = 0.86). A decision rule (defined as positive if prior antibiotic use and either significant diarrhea or abdominal pain are present) demonstrated sensitivity and specificity of 86 and 45%. When applied to the entire dataset (N = 480), a simplified a priori rule, defined as positive if both prior antibiotic use and history of significant diarrhea are present, demonstrated sensitivity, specificity, positive and negative predictive value of 80, 45, 18 and 94%, respectively (6% of those predicted to be cytotoxin-negative actually tested positive). Use of this rule would have averted 39% of cytotoxin assays in our study population.

CONCLUSIONS

Patients without prior antibiotic use and either significant diarrhea or abdominal pain are unlikely to have positive C difficile cytotoxin assay results, and may not routinely require cytotoxin testing.

Ras, Rap, and Rac small GTP-binding proteins are targets for Clostridium sordellii lethal toxin glucosylation

Lethal toxin (LT) from Clostridium sordellii is one of the high molecular mass clostridial cytotoxins. On cultured cells, it causes a rounding of cell bodies and a disruption of actin stress fibers. We demonstrate that LT is a glucosyltransferase that uses UDP-Glc as a cofactor to covalently modify 21-kDa proteins both in vitro and in vivo. LT glucosylates Ras, Rap, and Rac. In Ras, threonine at position 35 was identified as the target amino acid glucosylated by LT. Other related members of the Ras GTPase superfamily, including RhoA, Cdc42, and Rab6, were not modified by LT. Incubation of serum-starved Swiss 3T3 cells with LT prevents the epidermal growth factor-induced phosphorylation of mitogen-activated protein kinases ERK1 and ERK2, indicating that the toxin blocks Ras function in vivo. We also demonstrate that LT acts inside the cell and that the glucosylation reaction is required to observe its dramatic effect on cell morphology. LT is thus a powerful tool to inhibit Ras function in vivo.

UDP-glucose deficiency in a mutant cell line protects against glucosyltransferase toxins from Clostridium difficile and Clostridium sordellii

We have previously isolated a fibroblast mutant cell with high resistance to the two Rho-modifying glucosyltransferase toxins A and B of Clostridium difficile. We demonstrate here a low level of UDP-glucose in the mutant, which explains its toxin resistance since: (i) to obtain a detectable toxin B-mediated Rho modification in lysates of mutant cells, addition of UDP-glucose was required, and it promoted the Rho modification dose-dependently; (ii) high pressure liquid chromatography analysis of nucleotide extracts of cells indicated that the level of UDP-glucose in the mutant (0.8 nmol/10(6) cells) was lower than in the wild type (3.7 nmol/10(6) cells); and (iii) sensitivity to toxin B was restored upon microinjection of UDP-glucose. Using the mutant as indicator cell we also found that the related Clostridium sordellii lethal toxin is a glucosyltransferase which requires UDP-glucose as a cofactor. Like toxin B it glucosylated 21-23-kDa proteins in cell lysates, but Rho was not a substrate for lethal toxin.

Increased substance P receptor expression by blood vessels and lymphoid aggregates in Clostridium difficile-induced pseudomembranous colitis

Pseudomembranous colitis is most often caused by toxins secreted by Clostridium difficile following bowel flora overgrowth after antibiotic use. The secretory and inflammatory effects observed in C. difficile toxin A-induced enterocolitis in the rat ileum are inhibited by CP-96,345, a substance P (SP) receptor antagonist. To determine if SP plays a role in the pathogenesis of human pseudomembranous colitis, SP receptor distribution was examined in a toxin A-positive specimen of bowel. Quantitative receptor autoradiography was used to examine SP receptors in tissue from a patient who tested positive for C. Difficile toxin. SP receptors were massively increased in small blood vessels and lymphoid aggregates in the pseudomembranous colitis bowel in comparison to control specimens. The SP binding was saturable and exhibited similar affinities for SP and CP-96,345. SP may contribute to the inflammatory response in pseudomembranous colitis via a massive increase in SP receptor antagonists may offer a novel therapeutic intervention for pseudomembranous colitis.

Community-acquired toxigenic Clostridium difficile diarrhoea in the normoxaemic elderly who have received no antimicrobials: soft evidence for ischaemic colitis?

We report three examples of community-acquired toxigenic Clostridium difficile diarrhoea in elderly patients who had neither received antimicrobial therapy nor been institutionalised. These cases stimulated interest in the non-antimicrobial changes which might predispose the host to C. difficile-related disease and raised the spectre of bowel ischaemia as a possible aetiological factor.

Anti-Clostridium difficile bovine immunoglobulin concentrate inhibits cytotoxicity and enterotoxicity of C. difficile toxins

Clostridium difficile diarrhea and colitis result from the actions of bacterial exotoxins on the colonic mucosa. This study examined the ability of hyperimmune bovine colostral antibodies to neutralize the biological effects of these toxins. Anti-C. difficile bovine immunoglobulin concentrate was prepared from the colostral milk of Holstein cows previously immunized with C. difficile toxoids. The anti-C. difficile bovine immunoglobulin concentrate contained high levels of bovine immunoglobulin G specific for C. difficile toxins A and B, as evaluated by enzyme-linked immunosorbent assay. Anti-C. difficile bovine immunoglobulin concentrate neutralized the cytotoxic effects of purified toxin A and toxin B on cultured human fibroblasts, whereas control bovine immunoglobulin concentrate had little toxin-neutralizing activity. Anti-C. difficile bovine immunoglobulin concentrate also blocked the binding of toxin A to its enterocyte receptor and inhibited the enterotoxic effects of C. difficile toxins on the rat ileum, as measured by an increased rat ileal loop weight/length ratio (63% inhibition; P < 0.01), increased mannitol permeability (92% inhibition; P < 0.01), and histologic grading of enteritis (P < 0.01 versus nonimmune bovine immunoglobulin concentrate). Thus, anti-C. difficile bovine immunoglobulin concentrate neutralizes the cytotoxic effects of C. difficile toxins in vitro and inhibits their enterotoxic effects in vivo. This agent may be clinically useful in the prevention and treatment of C. difficile diarrhea and colitis.

Effects of anti-inflammatory drugs on fever and neutrophilia induced by Clostridium difficile toxin B

This study investigated the ability of Clostridium difficile toxin B, isolated from the VPI 10463 strain, to induce fever and neutrophilia in rats. Intravenous injection of toxin B (0.005–0.5 μg/kg) evoked a dose-dependent increase in body temperature. The febrile response to 0.5 μg/kg of the toxin started in 2.5 h, peaked at 5 h, and subsided fully within 24 h. Toxin B also induced a dosedependent neutrophilia. Pretreatment with indomethacin (2 mg/kg, i.p.) did not affect the neutrophilia induced by toxin B, but significantly reduced the febrile response measured 4 to 8 h after toxin B injection. Dexamethasone (0.5 mg/ kg) also markedly diminished the febrile response induced by toxin B. These results show that Clostridium difficile toxin B induced a febrile response susceptible to inhibition by dexamethasone and indomethacin. Furthermore, they suggest that prostaglandins are not involved in the neutrophilia caused by this toxin.

Clostridium difficile infection

The spore-forming anaerobe Clostridium difficile has become a serious enteropathogen. Changes in the composition of natural intestinal flora, mainly due to antibiotic therapy, permit its colonization of, and multiplication in, the colon. The disease is caused by (entero)toxin A and (cyto)toxin B, and infection ranges from asymptomatic carrier state and mild diarrhea to pseudomembranous colitis. The clinical diagnosis is made by observing inflammatory, sometimes bloody, diarrhea and by the colonoscopic detection of epithelial necrosis, ulceration, and, in the advanced state, pseudomembrane formation. The laboratory supports the diagnosis by detecting toxin A and/or B by an enzyme-linked immunoassay with high specificity, but sometimes less sensitivity than with the cytotoxin assay in tissue culture cells. Fecal leukocytes or fecal lactoferrin may be found. Culture for the isolation and identification of toxigenic C. difficile is time consuming but necessary for epidemiological studies. Polymerase chain reaction (PCR) tests have been tested for detection of the toxin B gene directly in stool. Therapy consists of stopping all systemic antibiotic treatment and the use of oral metronidazole or vancomycin. There may be more relapses after vancomycin therapy, and the increasing vancomycin resistance of Enterococcus is worrisome. Prevention, especially of nosocomial spread, requires isolation and enforced handwashing. For epidemiological studies, the bacteria can be typed by molecular DNA analyses, including PCR, protein electrophoresis, and immunological tests.

Clostridium difficile-associated diarrhea and colitis

OBJECTIVES

To review and summarize the status of diagnosis, epidemiology, infection control, and treatment of Clostridium difficile-associated disease (CDAD).

DIAGNOSIS

A case definition of CDAD should include the presence of symptoms (usually diarrhea) and at least one of the following positive tests: endoscopy revealing pseudomembranes, stool cytotoxicity test for toxin B, stool enzyme immunoassay for toxin A or B, or stool culture for C difficile (preferably with confirmation of organism toxicity if a direct stool toxin test is negative or not done). Testing of asymptomatic patients, including those who are asymptomatic after treatment, is not recommended other than for epidemiologic purposes. Lower gastrointestinal endoscopy is the only diagnostic test for pseudomembranous colitis, but it is expensive, invasive, and insensitive (51% to 55%) for the diagnosis of CDAD. Stool culture is the most sensitive laboratory test currently in clinical use, but it is not as specific as the cell cytotoxicity assay.

EPIDEMIOLOGY

C difficile is the most frequently identified cause of nosocomial diarrhea. The majority of C difficile infections are acquired nosocomially, and most patients remain asymptomatic following acquisition. Antimicrobial exposure is the greatest risk factor for patients, especially clindamycin, cephalosporins, and penicillins, although virtually every antimicrobial has been implicated. Cases of CDAD unassociated with prior antimicrobial or antineoplastic use are very rare. Hands of personnel, as well as a variety of environmental sites within institutions, have been found to be contaminated with C difficile, which can persist as spores for many months. Contaminated commodes, bathing tubs, and electronic thermometers have been implicated as sources of C difficile. Symptomatic and asymptomatic infected patients are the major reservoirs and sources for environmental contamination. Both genotypic and phenotypic typing systems for C difficile are available and have enhanced epidemiologic investigation greatly.

INFECTION CONTROL

Successful infection control measures designed to prevent horizontal transmission include the use of gloves in handling body substances and replacement of electronic thermometers with disposable devices. Isolation, cohorting, handwashing, environmental disinfection, and treatment of asymptomatic carriers are recommended practices for which convincing data of efficacy are not available. The most successful control measure directed at reduction in symptomatic disease has been antimicrobial restriction.

TREATMENT

Treatment of symptomatic (but not asymptomatic) patients with metronidazole or vancomycin for 10 days is effective; metronidazole may be preferred to reduce risk of vancomycin resistance among other organisms in hospitals. Recurrence of symptoms occurs in 7% to 20% of patients and is due to both relapse and reinfection. Over 90% of first recurrences can be treated successfully in the same manner as initial cases. Combination treatment with vancomycin plus rifampin or the addition orally of the yeast Saccharomyces boulardii to vancomycin or metronidazole treatment has been shown to prevent subsequent diarrhea in patients with recurrent disease.

Use of pulsed-field gel electrophoresis for investigation of an outbreak of Clostridium difficile infection among geriatric patients

A six-month outbreak of Clostridium difficile infection among elderly residents of a middle-term-care facility was investigated. Pulsed-field gel electrophoresis was used to genotype 22 outbreak strains and 30 epidemiologically unrelated strains. A prospective case-control study was conducted to identify risk factors for epidemic Clostridium difficile-associated diarrhea. All epidemiologically unrelated Clostridium difficile strains of the same serogroup could be differentiated by their DNA patterns with two restriction enzymes (SmaI and KspI). Among clustered strains, two epidemic serogroups (C and K) were identified. Two different DNA patterns were identified among serogroup C strains and three among serogroup K strains. Multivariate analysis showed that the risk of Clostridium difficile infection increased with antimicrobial chemotherapy (beta-lactam agents and pristinamycin) and the presence of a feeding tube. This study confirms the high discriminative power of restriction fragment length polymorphism analysis by pulsed-field gel electrophoresis to describe Clostridium difficile epidemiology. The typing results confirm that infection was principally exogenous in this outbreak. Furthermore, they indicate the need to improve all measures limiting transmission of infection.

[A rare cause of severe diarrhea in children: pseudomembranous colitis]

BACKGROUND

Pseudomembranous colitis is a rare and serious complication of treatment by antibiotics. The case of a patient with a protracted pseudomembranous colitis followed by two relapses is reported.

CASE REPORT

A 4 year-old boy was admitted after 18 days of profuse and feverish diarrhea. He had been given amoxycillin for 10 days, one and a half months previously. His temperature was 40 degrees C; he had abdominal pain and leucocytosis was 30,000/mm3. The situation rapidly improved with digestive rest and i.v. antibiotic therapy. Relapse of diarrhea together with bilious vomiting and acute abdominal pains required readmission three days after his discharge. Search for Clostridium difficile in stools remained negative. The diagnosis of pseudomembranous colitis was confirmed by sigmoidoscopy and intestinal biopsy. The patient was given parenteral nutrition for 3 weeks and vancomycin. The disease was complicated by anasarca related to severe protein-loosing enteropathy but evolution was finally favourable after a two month period.

CONCLUSION

Pseudomembranous colitis remains a serious affection in childhood; its prognosis largely depends on the precocity of diagnosis and treatment.

The toxigenic element of Clostridium difficile strain VPI 10463

The toxigenic element of Clostridium difficile strain VPI 10463 is identified by establishing boundaries between toxigenic sequences and those sequences shared by nontoxigenic and toxigenic strains. The toxigenic element is chromosomal, 19.6 kb in length, and comprised of five open reading frames which include the toxin A and B genes. Four of the open reading frames are contiguous and are transcribed in the same direction. The fifth is downstream from the others and oriented in the opposite direction. One of the open reading frames, located 5' to the toxin B gene, is previously unknown. Both upstream (5') and downstream (3') boundaries for the toxigenic element were examined in six toxigenic strains which vary considerably in toxigenicity to determine if there were variations among their respective toxigenic elements. The toxigenic element is highly conserved in these six strains. In the three nontoxigenic strains examined, a short fragment (127 bp) occupies the same chromosomal location as the large 19.6 kb toxigenic element.

Effects of purified Clostridium difficile toxin A on rabbit distal colon

BACKGROUND & AIMS

Antibiotic-associated pseudomembranous colitis in humans is caused by proliferation of Clostridium difficile, which elaborates an enterotoxin toxin A that causes epithelial damage and altered motility in rabbit small intestine. The aim of this study was to assess the effects of toxin A on rabbit distal colonic motility and to relate this to histological damage and inflammatory mediator production.

METHODS

Two hundred micrograms per milliliter of toxin A was placed in a distal colonic loop in anesthetized rabbits, and myoelectric activity was recorded for the following 7 hours. The colon was histologically evaluated and assayed for eicosanoid production. The effects of toxin A on longitudinal and circular muscle were also assessed in vitro.

RESULTS

Beginning 1 hour after instillation, toxin A caused a significant increase in the number of spike bursts without altering slow wave frequency; this was associated with an increase in mucosal neutrophils and increased production of prostaglandin E2 and leukotrienes B4 and C4/D4/E4. Seven hours after administration of toxin A, mediator levels and myoelectric activity remained increased but significant mucosal damage was now also present. Toxin A did not affect longitudinal or circular muscle in vitro.

CONCLUSIONS

C. difficile toxin A caused a significant neutrophil infiltration and an increased myoelectric activity before producing mucosal damage. The myoelectric effect may be indirect, resulting from the production of motility-altering arachidonic acid metabolites.

Rapid polymerase chain reaction method for specific detection of toxigenic Clostridium difficile

A rapid polymerase chain reaction (PCR) method for detection of toxigenic Clostridium difficile directly from fecal samples by amplification of toxin A gene fragments was investigated. The technique was applied to monitor the spread of the microorganism in a long-term care ward with a relatively high incidence of overt episodes of diarrhea. The PCR approach has several advantages over traditional methods, rapidly allowing the specific detection of toxigenic Clostridium difficile strains from stool samples in both symptomatic and asymptomatic subjects with toxigenic strains. This PCR method allows early detection of toxigenic Clostridium difficile and could thus represent a powerful tool for the surveillance of epidemics.

Concurrence of Clostridium difficile toxin A enzyme-linked immunosorbent assay, fecal lactoferrin assay, and clinical criteria with C. difficile cytotoxin titer in two patient cohorts

The accurate and sensitive diagnosis of Clostridium difficile-related diarrhea, normally treated with vancomycin, has become increasingly important in light of the emergence of dangerous new strains of vancomycin-resistant enterococci. In order to improve the threshold for C. difficile diagnosis and treatment, a number of commonly used assays for the diagnosis of C. difficile diarrhea were examined. These included an enzyme-linked immunosorbent assay for C. difficile toxin A (ToxA), a CHO cell culture assay for fecal C. difficile (cyto)toxin B, and a lactoferrin latex agglutination assay for fecal lactoferrin (LFLA). We studied 722 fecal specimens submitted by physicians for C. difficile toxin testing at the Salem, Va., Veterans' Affairs Hospital and at the University of Virginia Medical Center in Charlottesville. Charts were reviewed from 123 Veterans' Hospital patients and 114 University of Virginia patients for clinical criteria indicative of C. difficile diarrhea. An increasing titer of CHO cell cytotoxicity was correlated with an increasing likelihood of ToxA positivity (5 to 90%), LFLA positivity (39 to 77%), and clinical agreement (28 to 85%). However, some data indicate that the CHO cell cytotoxicity assay may be nonspecific when positive only at low titers. When the CHO assay result is positive at high titers, it remains the best diagnostic tool. Yet, when it is positive at a low titer, careful interpretation of the results in conjunction with other assays and the clinical setting is warranted, especially in light of new drug-resistant strains of microorganisms.

The enterotoxin from Clostridium difficile (ToxA) monoglucosylates the Rho proteins

The enterotoxin from Clostridium difficile (ToxA) is one of the causative agents of the antibiotic-associated pseudomembranous colitis. In cultured monolayer cells ToxA exhibits cytotoxic activity to induce disassembly of the actin cytoskeleton, which is accompanied by morphological changes. ToxA-induced depolymerization of actin filaments is correlated with a decrease in the ADP-ribosylation of the low molecular mass GTP-binding Rho proteins (Just, I., Selzer, J., von Eichel-Streiber, C., and Aktories, K. (1995) J. Clin. Invest. 95, 1026-1031). Here we report on the identification of the ToxA-induced modification of Rho. Applying electrospray mass spectrometry, the mass of the modification was determined as 162 Da, which is consistent with the incorporation of a hexose into Rho. From several hexoses tested UDP-glucose selectively served as cosubstrate for ToxA-catalyzed modification. The acceptor amino acid of glucosylation was identified from a Lys-C-generated peptide by tandem mass spectrometry as Thr-37. Mutation of Thr-37 to Ala completely abolished glucosylation. The members of the Rho family (RhoA, Rac1, and Cdc42Hs) were substrates for ToxA, whereas H-Ras, Rab5, and Arf1 were not glucosylated. ToxA-catalyzed glucosylation of lysates from ToxA-pretreated rat basophilic leukemia (RBL) cells resulted in a decreased incorporation of [14C]glucose, indicating previous glucosylation in the intact cell. Glucosylation of the Rho subtype proteins appears to be the molecular mechanism by which C. difficile ToxA mediates its cytotoxic effects on cells.

Glucosylation of Rho proteins by Clostridium difficile toxin B

Toxin A and B, the major virulence factors of Clostridium difficile, are the causative agents of antibiotic-associated pseudomembranous colitis. In cultured cell lines their potent cytotoxicity results from their ability to induce disaggregation of the microfilament cytoskeleton. Toxin B acts on the low-molecular-mass GTPase RhoA, which is involved in the regulation of the actin cytoskeleton. We report here that toxin B catalyses the incorporation of up to one mole of glucose per mole of RhoA at the amino acid threonine at position 37. The modification was identified and localized by tandem electrospray mass spectrometry. UDP-glucose selectively serves as cosubstrate for the monoglucosylation reaction catalysed by toxin B. Microinjection of RhoA previously glucosylated by toxin B into monolayer cells caused disaggregation of actin filaments, indicating a dominant-negative activity of glucosylated RhoA.

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.

Role of platelet activating factor in the inflammatory and secretory effects of Clostridium difficile toxin A

Clostridium difficile is a major recognized cause of antibiotic-associated diarrhea, an effect mediated through its toxin A. Toxin A has been reported to disrupt epithelial tight junctions, attract neutrophils, and cause striking intestinal inflammation and secretion. Having demonstrated that phospholipase A2 inhibitors block the secretory effects of toxin A, we next wished to examine whether platelet activating factor (PAF) was involved in either the direct epithelial or secretory effects of toxin A. The effects of toxin A on net secretion in ligated rabbit ileal segments were significantly inhibited by the PAF antagonists 10(-4)-10(-5) M BN 52021, 10(-5) M WEB 2170, or 10(-5) M SR 27417 by 59-102%. SR 27417 also inhibited secretion induced by toxin A in loops adjacent to the drug (by 58%). Furthermore, the striking inflammation and epithelial disruption seen at 6 h and ligated ileal segments with toxin A was largely prevented by simultaneous treatment with the PAF antagonist SR 27417. In addition, we noted a significant synergistic effect of 10(-8) M PAF with 10 micrograms/ml toxin A in the ligated rabbit ileal segments. To examine direct effects of PAF antagonists on toxin A in T-84 epithelial cell monolayers, rhodamine-labeled phalloidin stained F-actin demonstrated significant disruption of F-actin by toxin A that was reduced by the PAF antagonist BN 52021 or WEB 2170. However, the PAF antagonists (10(-4) M WEB, 10(-5) M BN or 10(-4) M SR) failed to alter the disruption of T-84 cell tissue resistance by C. difficile toxin A (0.03 micrograms/ml). We conclude that PAF may be involved in the secretory effects of C. difficile toxin A, and that PAF antagonists deserve further study in C. difficile diarrhea.

PCR amplification of rRNA intergenic spacer regions as a method for epidemiologic typing of Clostridium difficile

From January to March 1993, a suspected outbreak of antibiotic-associated diarrhea occurred on a pediatric oncology ward of the Clinical Center Hospital at the National Institutes of Health. Isolates of Clostridium difficile obtained from six patients implicated in this outbreak were typed by both PCR amplification of rRNA intergenic spacer regions (PCR ribotyping) and restriction endonuclease analysis of genomic DNA. Comparable results were obtained with both methods; five of the six patients were infected with the same strain of C. difficile. Subsequent analysis of 102 C. difficile isolates obtained from symptomatic patients throughout the Clinical Center revealed the existence of 41 distinct and reproducible PCR ribotypes. These data suggest that PCR ribotyping provides a discriminatory, reproducible, and simple alternative to conventional molecular approaches for typing strains of C. difficile.

[Severe forms of pseudomembranous colitis caused by Clostridium difficile]

Clostridium difficile causes a broad spectrum of enteric diseases in humans, ranging from mild antibiotic-associated diarrhoea to more severe pseudomembranous colitis. The authors report four cases of life-threatening pseudomembranous colitis with haemodynamic changes. Infection due to Clostridium difficile should be kept in mind whenever a patient undergoing antibiotic therapy develops a symptomatology of an acute abdomen.

The effect of Clostridium difficile toxin on colonocyte prostanoid activity

Antibiotic-associated colitis is caused by Clostridium difficile toxin. However, the pathophysiology of this entity is poorly understood. The aim of this study was to determine the effects of C. difficile toxin on colonocyte cyclooxygenase and phospholipase A2 (PLA2) activity. A transformed colonocyte cell line (Caco-2) was grown to confluency on 6 well plates. The cells were stimulated with graded concentrations of C. difficile toxin. In separate experiments, the cells were pretreated for one hour prior to stimulation with the cyclooxygenase inhibitor, indomethacin, or the glucocorticoid, dexamethasone. The culture media was collected one hour following C. difficile stimulation. Prostaglandin E2 (PGE2), 6-keto prostaglandin F1 alpha (6KPGF), thromboxane B2 (TxB2) and leukotriene B4 (LTB4) levels were determined in the media by an ELISA. Platelet activating factor (PAF) concentration was determined by a RIA. C. difficile toxin stimulated PGE2 and 6KPGF levels in a dose dependent fashion but failed to stimulate TxB2, LTB4 or PAF. Prostanoid production was inhibited by indomethacin dose dependently but was not inhibited by dexamethasone. The presence of indomethacin resulted in production of PAF. Our results show that the effects of C. difficile toxin on colonocytes are mediated by cyclooxygenase activity. The increase in PAF formation associated with indomethacin administration suggests that the prostanoids modulate PLA2 activity and inhibit PAF formation.

Clostridium sordellii cytotoxin induces phosphorylation of an 80,000 mol. wt protein in McCoy cultured cells

The cytotoxins from Clostridium difficile (toxin B) and Clostridium sordellii (toxin L) induce rounding of cultured cells. The cellular effects induced by these two cytotoxins are clearly distinct, suggesting that both toxins use a similar, but not identical mechanism for cell intoxication. We have employed the technique of two-dimensional PAGE for the separation of 32P-labelled cell lysates of McCoy cultured cells to investigate changes in the phosphorylation status of cellular proteins after treatment with toxin B and with toxin L. The two-dimensional electrophoresis patterns suggest the implication of an 80,000 mol. wt cellular protein (named pp80c) in the cytopathic action of the cytotoxin from C. sordellii. This protein shows immunoreactivity with non-muscle caldesmon. Toxin B, however, does not affect the phosphorylation of pp80c, but alters the phosphorylation of another cellular protein, pp77, indicating another mechanism for cell intoxication. In addition, our experiments suggest that the mechanism of action of okadaic acid, a phosphatase inhibitor which causes cell rounding similar to that induced by C. sordellii, and these two cytotoxins are different.

Clinical significance of Clostridium difficile and its toxins in faeces of immunocompromised children

In this study, clinical and laboratory findings were tested for correlation with the presence of Clostridium difficile. The toxigenicity of the isolated strains and the toxins were determined in faecal samples of immunocompromised children admitted to a single room for protective isolation. Using the toxin assay as the gold standard, the culture sensitivity of toxigenic C difficile was 94.1%, the specificity 93.8%, the positive predictive value 62.8%, and the negative predictive value 99.3%. Correction for stools with a positive culture of toxigenic C difficile preceding detection of toxin, resulted in a positive prediction value of 78.4%. A statistically significant association was found between a positive faecal toxin assay and fever, and between a positive culture of toxigenic C difficile and abdominal pain: 42% of the patients with positive toxin assays had fever versus 21% with negative toxin assays, and 66% of the patients with a positive culture for toxigenic C difficile had abdominal pain, versus 22% with negative cultures. Further analysis of the cultures and toxin assays showed no statistically significant association with diarrhoea, fever, white blood cell count, C reactive protein concentrations, or abdominal pain. Based on these findings, it is suggested that immunocompromised children should be treated when toxigenic C difficile is cultured or when toxin is detected in stool samples.

Cloning of a genetic determinant from Clostridium difficile involved in adherence to tissue culture cells and mucus

Our laboratory has previously shown that Clostridium difficile adherence to Caco-2 cells is greatly enhanced after heat shock at 60 degrees C and that it is mediated by a proteinaceous surface component. The experiments described here show that C. difficile could adhere to several types of tissue culture cells (Vero, HeLa, and KB) after heat shock. The type of culture medium (liquid or solid, with or without blood) had little effect on adhesion. To clone the adhesin gene, polyclonal antibodies against C. difficile heated at 60 degrees C were used to screen a genomic library of C. difficile constructed in lambda ZapII. Ten positive clones were identified in the library, one of which (pCL6) agglutinated several types of erythrocytes in the presence of mannose. In Western blots (immunoblots), this clone expressed in Escherichia coli a 40- and a 27-kDa protein; a 27-kDa protein has been previously identified in the surface extracts of heat-shocked C. difficile as a possible adhesin. The clone adhered to Vero, Caco-2, KB, and HeLa cells; the adherence was blocked by anti-C. difficile antibodies, by a surface extract of C. difficile, and by mucus isolated from axenic mice. Furthermore, the clone could attach ex vivo to intestinal mucus isolated from axenic mice. Preliminary studies on the receptor moieties implicated in C. difficile adhesion revealed that glucose and galactose could partially block adhesion to tissue culture cells, as did di- or trisaccharides containing these sugars, suggesting that the adhesin is a lectin. In addition, N-acetylgalactosamine, a component of mucus, and gelatin partially impeded cell attachment.

Evaluation of three commercial enzyme immunoassay kits for detecting faecal Clostridium difficile toxins

The detection of faecal cytotoxicity using tissue culture was compared with three commercial Clostridium difficile enzyme immunoassay (EIA) kits; Premier C difficile toxin A (Meridian Diagnostic, Inc.); CD-TOX C difficile toxin A (Porton Cambridge); and Cytoclone A+B EIA (Cambridge Biotech Corporation). Of 160 faecal samples examined by all four methods, 52 (32.5%) were cytotoxic, 44 (27.5%) were positive by Premier, 48 (30%) by CD-TOX EIA, and 50 (31.3%) with Cytoclone. When compared with detection of cytotoxicity by tissue culture assay, the following performance indices were obtained: Premier, sensitivity 84.1%, specificity 99.1%, positive predictive value (PPV) 97.8%, negative predictive value (NPV) 93%; CD-TOX, sensitivity 92.3%, specificity 88.0%, PPV 78.7%, NPV 95.9%; Cytoclone, sensitivity 96.2%, specificity 93.5%, PPV 87.7%, NPV 98.1%. EIA results were available within three hours, whereas the results of the cytotoxin assay were available after 24-48 hours. All three kits provided satisfactory results and, although relatively expensive, all could be used in the laboratory effectively to screen for diarrhoeal disease associated with C difficile.

Evaluation of an enzyme immunoassay kit for the detection of Clostridium difficile enterotoxin

The Premier Clostridium difficile toxin A enzyme immunoassay (EIA) kit was evaluated for the detection of C. difficile enterotoxin in fecal samples. A total of 314 samples was tested by culture, cytotoxin detection and EIA kit. Compared to a combined culture/cytotoxin result the Premier EIA kit had a sensitivity of 88.3%, a specificity of 100%, a predictive value positive of 100% and a predictive value negative of 87.4%. Test results were available within 3 hrs providing a rapid and reliable means of detecting C. difficile enterotoxin.

Comparison of TechLab Clostridium difficile Tox-A enzyme immunoassay and Bartels Prima system toxin-A EIA

We evaluated the Bartles Clostridium difficile toxin A test and the TechLab Tox-A test to detect C. difficile toxin A in stool. The results were compared with C. difficile cytotoxicity assays. Of the 463 specimens tested 82 (17.7%) tested positive by cytotoxicity assay. The sensitivity, specificity, and positive and negative predictive values of the TechLab EIA were 86.6%, 93.7%, 74.7%, and 97.0%, respectively. For the Bartels Prima EIA, sensitivity, specificity, and positive and negative predictive values were 95.1%, 95.5%, 82.1%, and 98.9%, respectively. The differences in sensitivity were statistically significant. Indeterminate results requiring repeat testing were more common with the TechLab EIA than with the Bartels Prima EIA. Of the two kits, the Bartels EIA is preferable, primarily because of its increased sensitivity.

Clostridium difficile-associated diarrhoea: epidemiological data from Western Australia

The incidence of Clostridium difficile-associated diarrhoea (CDAD) was investigated retrospectively at a 690-bed teaching hospital for the period 1983-92. Our aims were to determine: (i) the distribution by age and sex of patients with CDAD, (ii) the possibility of a seasonal trend and, (iii) the influence of infection control procedures, contamination of the hospital environment and the use of third-generation cephalosporins. The laboratory diagnosis of CDAD was based on demonstration of the organism by stool culture and/or detection of specific cytotoxin in stool filtrates. C. difficile was detected in 917 patients who were being investigated for diarrhoeal illness. Yearly isolations varied from a low of 49 in 1983 to a high of 120 in 1990 (Chi square for linear trend 128.8; P < 0.005). Most patients were elderly, with 63% aged 60 years or more; the majority (59%) were female. The relationship between culture of C. difficile and detection of cytotoxin in faecal extracts was also examined. Sixty percent of a sample of 132 isolates from patients in whom faecal cytotoxin was not detected produced cytotoxin in vitro, suggesting that culture is a more sensitive indicator of infection with C. difficile than cytotoxin detection. When the total number of faecal specimens received in the laboratory was used as a denominator there was an increase in the number of incident cases of CDAD between 1983 and 1990, apart from 1986. When occupied bed days was used as the denominator a similar trend was observed with a peak in 1990.(ABSTRACT TRUNCATED AT 250 WORDS)

Patterns and prognosis of Clostridium difficile colitis

The incidence of Clostridium difficile colitis has increased during recent years, presumably because of liberal use of broad-spectrum antibiotic regimens.

METHODS

A retrospective review to determine patterns of C. difficile colitis development, morbidity, and treatment results was undertaken. During an 18-month period, 90 patients were diagnosed with C. difficile colitis by fecal toxin assays. Patient demographics, symptoms, previously administered antibiotic regimens, diagnostic evaluations, treatment modalities, morbidity, and mortality were identified, entered into a computer data base, and analyzed.

RESULTS

The mean age was 58 years; males outnumbered females 1.2:1. Among 90 patients, 41 (46 percent) developed C. difficile colitis after surgical procedures. Eighty (89 percent) patients received antibiotic therapy before developing C. difficile colitis: 35 (44 percent) for documented infections and 45 (56 percent) as empiric or prophylactic therapy. Cephalosporins, penicillins, quinolones, vancomycin, and aminoglycosides were the most frequently administered antibiotic classes prior to C. difficile colitis diagnosis. Ten (11 percent) patients developed C. difficile colitis without previous antibiotic therapy. Eighty-two (91 percent) patients presented with diarrhea, while eight (9 percent) had fever only. Primary C. difficile colitis treatment for both groups included vancomycin (66 percent), metronidazole (24 percent), or both drugs (10 percent). Ten (11 percent) patients received no treatment. No patient developed toxic colitis or megacolon. Colonoscopy was performed in four (4 percent) patients; pseudomembranes were identified in one (25 percent) patient. There was one C. difficile colitis recurrence after treatment, but no C. difficile colitis-associated morbidity. Mortality (14 patients, 16 percent) was not related to C. difficile colitis, but to underlying illness. No difference in patient age, sex, previous antibiotic administration, serum albumin, total days hospitalized, duration of C. difficile colitis antibiotic therapy, C. difficile colitis treatment regimens, or mortality was identified between nonsurgical and surgical patients. The white blood cell count was significantly lower in the nonsurgical group however. Clostridium difficile colitis developed most commonly after antibiotic administration with symptoms of diarrhea, but did occur without previous antibiotic administration or diarrhea.

CONCLUSION

Despite the clinical setting, C. difficile colitis had no associated morbidity and treatment was highly effective. Mortality was related to underlying medical illness, not C. difficile colitis.

Evaluation of an oligonucleotide probe and an immunological test for direct detection of toxigenic Clostridium difficile in stool samples

A 33 basepair oligonucleotide probe, designed from the sequence of the Clostridium difficile toxin B gene, was evaluated for its ability to detect toxigenic Clostridium difficile directly in stool samples, without culture or DNA isolation. Two different labelling techniques were investigated: radiolabelling and digoxigenin-labelling. One hundred ninety-six stools were tested, with a good correlation (96%) obtained between the oligonucleotide probe and the gold standard, the cytotoxicity tissue culture assay. The sensitivity and specificity were 83% and 100%, respectively. In parallel, a new commercially available enzyme immunoassay for the detection of Clostridium difficile toxin A in stool specimens was investigated. In 162 samples tested, a sensitivity of 80% and a specificity of 98% were obtained.

Fecal shedding of Clostridium difficile in dogs: a period prevalence survey in a veterinary medical teaching hospital

The goal of this study was to determine the fecal prevalence of Clostridium difficile in dogs who were patients at a veterinary medical teaching hospital. Stool specimens collected from 152 dogs (in- and outpatients) were analyzed for the presence of C. difficile. An additional 42 stool specimens were collected and examined from dogs recently housed at local animal shelters. Following culture on selective medium, C. difficile was identified by a latex agglutination test, and the presence of the toxin A and B genes was determined individually by polymerase chain reaction. Clostridium difficile was isolated from the feces of 28 of the veterinary hospital patients (18.4%); isolates from 14 of these patients (50.0%) were toxigenic. Diarrhea was a clinical finding in 5 (35.7%) of the dogs carrying toxigenic isolates of C. difficile, whereas diarrhea was noted in only 2 of 14 dogs (14.3%) shedding nontoxigenic isolates. Three of 14 dogs (21.4%) shedding toxigenic isolates of C. difficile were receiving antibiotics at the time of stool collection, whereas 5 of 14 dogs (37.5%) shedding nontoxigenic strains of C. difficile were receiving antibiotics. The carriage rate of C. difficile was significantly higher for animals categorized as inpatients of the veterinary hospital. The carriage rate also provided evidence for an increased risk for fecal shedding with increasing age. Clostridium difficile was not isolated from any of the 42 dogs recently housed at local animal shelters. This study confirms the presence of toxigenic C. difficile in dogs at a veterinary teaching hospital.(ABSTRACT TRUNCATED AT 250 WORDS)

Development and clinical evaluation of an amplified flow cytometric fluoroimmunoassay for Clostridium difficile toxin A

A rapid (2 h) amplified flow cytometric fluoroimmunoassay (AFCF) for Clostridium difficile toxin A was developed and compared with the cytotoxin assay (CTA) and culture of the organism from stool specimens from patients with suspected C. difficile-associated gastrointestinal disease (CAD). For this assay polyclonal antitoxin A was attached to 10-microns diameter and monoclonal antitoxin A was attached to fluorescent 0.1 micron-diameter polystyrene microspheres. The microspheres and sample were reacted together as in a conventional double-antibody sandwich assay. However, laser flow cytometric measurement allowed the omission of separation and washing steps by gating on light scattered by the larger microspheres and measuring only the fluorescence associated with these particles. The amount of fluorescence from the attached 0.1 micron microspheres was dependent on the concentration of toxin A in the sample. The AFCF detected purified toxin A at levels of 1 pg/ml and was linear from 1 to 40 pg/ml. The AFCF was compared with the CTA and culture of C. difficile for clinical use by comparing results from 198 stool specimens from patients with suspected CAD. The AFCF was 85.7% sensitive and 95.8% specific relative to the CTA, and 85.2% sensitive and 98.3% specific compared to the culture assay. If the isolation of toxigenic C. difficile or the patients clinical course was considered indicative of CAD, the sensitivities of the AFCF, CTA, and culture assay were 77.4%, 67.7% and 96.8%, respectively. The AFCF demonstrated a specificity of 98.8%, while both CTA and culture had a specificity of 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Probing the action of Clostridium difficile toxin B in Xenopus laevis oocytes

Clostridium difficile toxin B and Clostridium botulinum C3 exoenzyme caused comparable morphological alteration of CHO cells, which was accompanied by disaggregation of the microfilamental cytoskeleton. The cytotoxic effect of toxin B was correlated with a decrease in C3-catalyzed ADP-ribosylation of the low-molecular-mass GTP-binding protein Rho, which is involved in the regulation of the actin cytoskeleton. We used Xenopus laevis oocytes as a model to study the toxin effect on Rho in more detail. Toxin B treatment of oocytes caused a decrease in subsequent ADP-ribosylation of cytoplasmic Rho by C3. This decrease was observed when toxin B was applied externally or after microinjection. Besides endogenous Rho, microinjected recombinant Rho-glutathione S-transferase fusion protein was affected. Impaired ADP-ribosylation of Rho was neither due to altered guanine nucleotide binding nor to complexation with the guanine nucleotide dissociation inhibitor, which is known to inactivate Rho and to prevent Rho modification by C3. Proteolytical degradation of Rho was excluded by immunoblot analysis. In intact oocytes toxin B caused neither ADP-ribosylation nor phosphorylation of Rho. The data indicate that C. difficile toxin B acts on Rho proteins in Xenopus oocytes to inhibit ADP-ribosylation by C3. It is suggested that toxin B mediates its cytotoxic effect via functional inactivation of Rho.

Comparison of four commercially available rapid enzyme immunoassays with cytotoxin assay for detection of Clostridium difficile toxin(s) from stool specimens

Rapid (2.5- to 3.5-h) enzyme immunoassays (EIAs) for the detection of Clostridium difficile toxins have been developed. We report the results of simultaneous testing of 700 fresh stool specimens by the tissue culture cytotoxin assay and four EIAs (Bartels Prima System C. difficile Toxin A EIA, Cambridge Biotech Cytoclone A+B EIA, Meridian Diagnostics Premier C. difficile Toxin A EIA, and TechLab C. difficile Tox-A Test EIA). In cases of disagreement, culturing for toxigenic C. difficile was performed. A total of 61 (8.7%) specimens from 46 patients were positive for C. difficile toxin. The sensitivity of the cytotoxin assay was 87%, and that of culture was 93%. In comparison with the cytotoxin assay results, the sensitivity and specificity of the EIAs were as follows: Bartels, 87 and 96%; Cambridge, 89 and 99%; Meridian, 87 and 98%; and TechLab, 87 and 95%, respectively. In comparison with the cytotoxin assay plus toxigenic culture results, the sensitivity and specificity of the EIAs were as follows: Bartels, 84 and 97%; Cambridge, 85 and 99%; Meridian, 79 and 98%; and TechLab, 80 and 96%, respectively. The EIAs varied in positive predictive values (PPVs). A high PPV was seen with the Cambridge EIA (96%); lower PPVs were seen with the TechLab (64%), Bartels (72%), and Meridian (80%) EIAs because of high false-positive rates. The negative predictive values (98 to 99%) were excellent with all EIAs. Results were indeterminant with 0.3% of the samples by the Meridian EIA and 3% by all the other EIAs. Although the EIAs were less sensitive than the cytotoxin assay, they provide same-day results and may be useful in laboratories without tissue culture facilities.

Neutrophil recruitment in Clostridium difficile toxin A enteritis in the rabbit

Neutrophil infiltration is a prominent feature of Clostridium difficile-associated enteritis and colitis. The aim of this study was to examine the importance of neutrophil recruitment and neutrophil-mediated tissue damage in C. difficile toxin A-induced enteritis. Competitive binding experiments using purified 3H-toxin A demonstrated the presence of a single class of medium affinity receptors on rabbit neutrophils (Kd 7 x 10(-8) M). Pertussis toxin and the nonhydrolyzable GTP analog GTPgamma S both inhibited 3H-toxin A binding (by 56 and 65%, respectively), indicating that the rabbit neutrophil toxin A receptor is G protein linked. Toxin A elicited a dose-dependent (25-200 micrograms/ml) stimulation of neutrophil migration in vitro, and this functional effect was also pertussis toxin sensitive (69% inhibition). Treatment of neutrophils with R15.7, a blocking monoclonal antibody to the leuocyte adhesion molecule CD18, inhibited toxin A-stimulated neutrophil migration by 85% in vitro. Pretreatment of rabbits with R15.7 also prevented neutrophil infiltration of toxin A-exposed ileal loops in vivo as determined by histologic examination and by ileal tissue myeloperoxidase levels. Furthermore, R15.7 effected a substantial inhibition of fluid secretion (by 65%), mannitol permeability (by 66%), and histologic damage in toxin A-exposed ileal loops. Anti-CD18 (R15.7) had no inhibitory effect on cholera toxin enterotoxicity. These data demonstrate that C. difficile toxin A is a proinflammatory toxin whose enterotoxic effects are substantially dependent upon neutrophil recruitment.

Human antibody response to Clostridium difficile toxin A in relation to clinical course of infection

This study investigated whether differences in fecal and serum antitoxin A antibody levels may account for the duration of Clostridium difficile-associated diarrhea (CDAD) and the occurrence of relapses. By an enzyme linked-immunosorbent assay, we tested 40 patients with CDAD including 25 patients without immunodeficiency and 15 patients receiving antineoplastic drugs. Two hundred eighty serum samples and 80 normal stool samples were investigated as controls. In nonimmunocompromised patients, serum immunoglobulin (IgG) and fecal IgA antitoxin A antibody titers were significantly higher in patients who suffered a single episode (n = 21) than in those with relapsing CDAD (n = 4) whose titers were at control levels. Of these 25 patients, eight suffered from diarrhea which lasted for more than 2 weeks. These patients had significantly lower serum- and feces-specific antibody levels than the others who presented symptoms of shorter duration. In cytostatic-treated patients, antitoxin A antibody levels were similar to controls, but relapses occurred in a single case. These data suggest an association between a defective humoral response to toxin A and a more severe form of C. difficile infection. They also indicate that other host-related factors control the severity of CDAD and remain to be elucidated.

Detection of Clostridium difficile toxin by enzyme immunoassay, tissue culture test and culture

Clostridium difficile toxin is frequently encountered in patients with antibiotic-associated diarrhea. A commercially available enzyme immunoassay (EIA) detecting toxins A and B was evaluated, screening 148 stool specimens specifically submitted for the detection of C. difficile. A sensitivity of 100% and a specificity of 97.5% were found compared to a tissue culture assay. The overall prevalence of C. difficile toxin was 22.1%. Cephalosporins had been administered significantly more often to toxin-positive patients. The EIA proved to be a suitable test for the detection of C. difficile toxin, revealing high prevalences in specifically submitted clinical specimens.