Multicenter evaluation of the Clostridium difficile TOX A/B TEST

The Relative Role of Toxins A and B in the Virulence of Clotridioides difficile

Most pathogenic strains of C. difficile possess two large molecular weight single unit toxins with four similar functional domains. The toxins disrupt the actin cytoskeleton of intestinal epithelial cells leading to loss of tight junctions, which ultimately manifests as diarrhea in the host. While initial studies of purified toxins in animal models pointed to toxin A (TcdA) as the main virulence factor, animal studies using isogenic mutants demonstrated that toxin B (TcdB) alone was sufficient to cause disease. In addition, the natural occurrence of TcdA−/TcdB+ (TcdA−/B+)mutant strains was shown to be responsible for cases of C. difficile infection (CDI) with symptoms identical to CDI caused by fully toxigenic (A+/B+) strains. Identification of these cases was delayed during the period when clinical laboratories were using immunoassays that only detected TcdA (toxA EIA). Our hospital laboratory at the time performed culture as well as toxA EIA on patient stool samples. A total of 1.6% (23/1436) of all clinical isolates recovered over a 2.5-year period were TcdA−/B+ variants, the majority of which belonged to the restriction endonuclease analysis (REA) group CF and toxinotype VIII. Despite reports of serious disease due to TcdA−/B+ CF strains, these infections were typically mild, often not requiring specific treatment. While TcdB alone may be sufficient to cause disease, clinical evidence suggests that both toxins have a role in disease.

Duodenitis-Proximal Jejunitis in Horses After Experimental Administration of Clostridium difficile Toxins

BACKGROUND

Duodenitis-proximal jejunitis (DPJ) is an acute sporadic gastrointestinal disorder of horses of unknown cause.

HYPOTHESIS/OBJECTIVES

We hypothesize that Clostridium difficile toxins are involved in the pathogenesis of DPJ in horses. The objective of this study was to determine whether experimentally delivered C. difficile toxins cause clinical signs and histologic lesions similar to those of naturally occurring DPJ.

ANIMALS

Six healthy mature mixed breed horses.

METHODS

Experimental study: animal model of animal disease. Fasted horses were administered crude C. difficile toxins via gastroscopy and monitored for up to 48 hour. Blood was collected for complete blood cell count, biochemistry profile, and plasma fibrinogen assay, and abdominal fluid was collected for cytologic analysis and total solids before and after toxin administration. Physical examination and abdominal ultrasonography were performed throughout the study period. Tissues were collected from the gastrointestinal tract and processed for routine histologic analysis, and lesions were scored.

RESULTS

Clinical signs were observed in 2 of 6 horses that are typical although not specific for horses with naturally occurring DPJ. Histopathologic lesions were observed in 6 of 6 horses and were similar to those reported in horses with naturally occurring DPJ. Two horses were severely affected.

CONCLUSIONS AND CLINICAL IMPORTANCE

Duodenitis-proximal jejunitis is likely a syndrome with multiple causes that result in the same clinical and pathologic findings, and our data suggest that the toxins of C. difficile represent one cause of this syndrome. Toxin dose and variation in individual animal susceptibility might affect the clinical signs and lesions after administration of C. difficile toxins.

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.

Molecular characterization and antimicrobial susceptibility of tcdA-negative Clostridium difficile isolates from Guangzhou, China

This study aimed to investigate the molecular characteristics and antimicrobial susceptibility of Clostridium difficile clinical isolates in Guangzhou, China. One hundred twenty isolates were collected from Guangzhou General Hospital at the Guangzhou Military Command in China from March 2014 to April 2015, and 9 isolates were identified as tcdA-negative/tcdB-positive (A(-)B(+)) strains. Results showed that all of the strains were confirmed to be ST37 and 0 single nucleotide variants (SNVs) were found in the PaLoc region, and >60 SNVs were identified throughout the whole genome sequence. The results show the diversity of the antibiotic and gene mutations present in these strains. All of the A(-)B(+) isolates were highly resistant to clindamycin and erythromycin; showed an average sensitivity to fluoroquinolones; and maintained a high susceptibility to metronidazole, vancomycin, and tigecycline.

Multiplex Real-Time PCR Method for Simultaneous Identification and Toxigenic Type Characterization of Clostridium difficile From Stool Samples

Background

The aim of this study was to develop and validate a multiplex real-time PCR assay for simultaneous identification and toxigenic type characterization of Clostridium difficile.

Methods

The multiplex real-time PCR assay targeted and simultaneously detected triose phosphate isomerase (tpi) and binary toxin (cdtA) genes, and toxin A (tcdA) and B (tcdB) genes in the first and sec tubes, respectively. The results of multiplex real-time PCR were compared to those of the BD GeneOhm Cdiff assay, targeting the tcdB gene alone. The toxigenic culture was used as the reference, where toxin genes were detected by multiplex real-time PCR.

Results

A total of 351 stool samples from consecutive patients were included in the study. Fifty-five stool samples (15.6%) were determined to be positive for the presence of C. difficile by using multiplex real-time PCR. Of these, 48 (87.2%) were toxigenic (46 tcdA and tcdB-positive, two positive for only tcdB) and 11 (22.9%) were cdtA-positive. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the multiplex real-time PCR compared with the toxigenic culture were 95.6%, 98.6%, 91.6%, and 99.3%, respectively. The analytical sensitivity of the multiplex real-time PCR assay was determined to be 103colonyforming unit (CFU)/g spiked stool sample and 0.0625 pg genomic DNA from culture. Analytical specificity determined by using 15 enteric and non-clostridial reference strains was 100%.

Conclusions

The multiplex real-time PCR assay accurately detected C. difficile isolates from diarrheal stool samples and characterized its toxin genes in a single PCR run.

Prevalence and characterization of enterotoxigenic Bacteroides fragilis and toxigenic Clostridium difficile in a Taipei emergency department

BACKGROUND/PURPOSE

Enterotoxigenic Bacteroides fragilis (ETBF) and toxin-encoding Clostridium difficile (TXCD) are associated with gastroenteritis. Routine anaerobic blood culture for recovery of these anaerobic pathogens is not used for the detection of their toxins, especially for toxin-variant TXCD. The aim of this study was to investigate the prevalence and risk factors of the genotypes of these anaerobes in patients with acute diarrheal illnesses.

METHODS

The data and samples of 513 patients with gastroenteritis were collected in a Taipei emergency department from March 1, 2006 to December 31, 2009. Nonenterotoxigenic B. fragilis (NTBF) and ETBF and the toxin genotypes of TXCD were detected by molecular methods.

RESULTS

The prevalence rates of NTBF, ETBF, and TXCD infections were 33.14%, 1.56%, and 2.34%, respectively. ETBF infections often occurred in the elderly (average age = 67.13 years) and during the cold, dry winters. TXCD infections were widely distributed in age and often occurred in the warm, wet springs and summers. The symptoms of ETBF-infected patients were significantly more severe than those of NTBF-infected patients.

CONCLUSION

This study identified and analyzed the prevalence, risk factors, and clinical presentations of these anaerobic infections. Future epidemiologic and clinical studies are needed to understand the role of ETBF and TXCD in human gastroenteritis.

[Characterization of a Toxin A-Negative, Toxin B-Positive Variant Strain of Clostridium difficile.]

BACKGROUND

Clostridium difficile is one of the most important pathogens responsible for nosocomial diarrhea. Recently, we have frequently experienced culture positive, toxin A enzyme immunoassay negative strains. Therefore, we evaluated the strains with several PCR primer sets to characterize them.

METHODS

A total of 351 stool specimens were examined for toxin A using enzyme linked fluorescent immunoassay (ELFA) and also cultured for C. difficile using cycloserine cefoxitine fructose agar incubated under anaerobic conditions. Spore stain and Vitek ANA identification card (BioMerieux, France) were used for identification of C. difficile. We amplified toxin A and toxin B genes in 81 isolates using primers NK1- NK2, NK3-NK2, NK9- NK11, and NK104-NK105.

RESULTS

The concordance rate between ELFA and culture was 65.2% (229/351). PCR for the toxin A gene using NK1-NK2, NK3-NK2 and for the toxin B gene using NK104-NK105 showed almost the same results. However, toxin A gene PCR using NK9-NK11 showed that 45.7% (37/81) of the evaluated strains were toxin A (-)/ toxin B(+) variant strains; thus, the corrected sensitivity and specificity of the ELFA based on the PCR results for toxin A and B genes were 65.6% and 100%, respectively.

CONCLUSIONS

The low sensitivity of the ELFA results for toxin A was due to the toxin A(-)/toxin B(+) variants of C. difficile, suggesting that the prevalence of the variant strains could be higher in Korea than was expected.

[Comparison of Two Enzyme Immunoassays for Clostridium difficile Toxin A.]

BACKGROUND

Clostridium difficile is one of the most important pathogens responsible for nosocomial diarrhea. The disease is mediated by two toxins, designated as A and B; therefore, identification of the toxins is important for diagnosis. However, culture or cytotoxin assay are not easily done because of tedious procedures. Instead, toxin A immunoassay is widely used. We evaluated two different enzyme immunoassays (EIA) for C. difficile toxin A and compared them with culture and PCR results.

METHODS

A total of 65 stool specimens were examined for toxin A using enzyme linked fluorescent immunoassay (ELFA, VIDAS CD II, Bio-Merieux, France) and enzyme linked immunosolvent assay (ELISA, C.DIFFICILE TOX A II, TECHLAB, USA ) and were also cultured for C. difficile using cycloserine cefoxitine fructose agar. We amplified toxin A and B genes using primers NK9-NK 11 and NK104-NK105, respectively, in 23 C. difficile isolates.

RESULTS

The concordance rate between ELFA and ELISA was 76.9%. The sensitivity and specificity of the ELFA and ELISA based on the culture and PCR results for toxin A gene were 84.6%/98.1% and 84.6%/67.3%. Positive and negative predictive values were 91%/96.2% in VIDAS and 78.0%/ 94.6% in TECHLAB. The positive rates of toxin B genes were 100%, 83.3% and 50% in toxin A positive, variant and negative strains, respectively.

CONCLUSIONS

The sensitivities of the ELFA and ELISA for toxin A were the same, but specificity and positive predictive value of the ELFA were higher than those of the ELISA. PCR or EIA method detecting both toxin A and toxin B is strongly recommended, because the variant strains (toxin A negative and toxin B positive) of C. difficile may be more prevalent than were anticipated in Korea.

Epidemiology of Clostridium difficile infections in a tertiary-care hospital in Korea

To survey healthcare-associated Clostridium difficile infection (HA-CDI) in a 900-bed tertiary-care hospital, we prospectively investigated the epidemiology of CDI and distribution of PCR-ribotypes. From February 2009 through January 2010, all patients with HA-CDI were enrolled. Epidemiological information and prescription records for antibiotics were collected. The C. difficile isolates were characterized using reference strains and were tested for antibiotic susceptibility. During the survey, incidence of HA-CDI was 71.6 per 100 000 patient-days. In total, 140 C. difficile isolates were obtained from 166 patients with HA-CDI. The PCR-ribotyping yielded 38 distinct ribotypes. The three most frequently found ribotypes made up 56.4% of all isolates; they comprised 37 isolates (26.4%) of PCR-ribotype 018, 22 (15.7%) of toxin A-negative PCR-ribotype 017, and 20 (14.3%) of PCR-ribotype 001. Clostridium difficile PCR-ribotype 018 was present in all departments throughout the hospital during the 11 months, whereas ribotype 017 and ribotype 001 appeared mostly in the pulmonary department. Hypervirulent C. difficile PCR-ribotype 027 was detected in 1 month on two wards. The incidence of CDI in each department showed a seven-fold difference, which correlated significantly with the amount of prescribed clindamycin (R = 0.783, p 0.013) or moxifloxacin (R = 0.733, p 0.025) in the departments. The rates of resistance of the three commonest ribotypes to clindamycin and moxifloxacin were significantly higher than those of other strains (92.1% versus 38.2% and 89.5% versus 27.3%, respectively). CDI is an important nosocomially acquired infection and this study emphasizes the importance of implementing country-wide surveillance to detect and control CDI in Korea.

Clinical importance and representation of toxigenic and non-toxigenic Clostridium difficile cultivated from stool samples of hospitalized patients

The aim of this study was to fortify the clinical importance and representation of toxigenic and non-toxigenic Clostridium difficile isolated from stool samples of hospitalized patients. This survey included 80 hospitalized patients with diarrhea and positive findings of Clostridium difficile in stool samples, and 100 hospitalized patients with formed stool as a control group. Bacteriological examination of a stool samples was conducted using standard microbiological methods. Stool sample were inoculated directly on nutrient media for bacterial cultivation (blood agar using 5% sheep blood, Endo agar, selective Salmonella Shigella agar, Selenite-F broth, CIN agar and Skirrow's medium), and to selective cycloserine-cefoxitin-fructose agar (CCFA) (Biomedics, Parg qe tehnicologico, Madrid, Spain) for isolation of Clostridium difficile. Clostridium difficile toxin was detected by ELISA-ridascreen Clostridium difficile Toxin A/B (R-Biopharm AG, Germany) and ColorPAC ToxinA test (Becton Dickinson, USA). Examination of stool specimens for the presence of parasites (causing diarrhea) was done using standard methods (conventional microscopy), commercial concentration test Paraprep S Gold kit (Dia Mondial, France) and RIDA(®)QUICK Cryptosporidium/Giardia Combi test (R-Biopharm AG, Germany). Examination of stool specimens for the presence of fungi (causing diarrhea) was performed by standard methods. All stool samples positive for Clostridium difficile were tested for Rota, Noro, Astro and Adeno viruses by ELISA - ridascreen (R-Biopharm AG, Germany). In this research we isolated 99 Clostridium difficile strains from 116 stool samples of 80 hospitalized patients with diarrhea. The 53 (66.25%) of patients with diarrhea were positive for toxins A and B, one (1.25%) were positive for only toxin B. Non-toxigenic Clostridium difficile isolated from samples of 26 (32.5%) patients. However, other pathogenic microorganisms of intestinal tract cultivated from samples of 16 patients. Examination of cultivated colonies revealed that most of cultivated species belonged to genera of Campylobacter spp., Salmonella spp., and Candida spp.. In control group, toxigenic Clostridium difficile cultivated from stool samples of two patients (2%) and non-toxigenic Clostridium difficile from samples of five patients (5%). This research confirmed clinical importance of toxigenic Clostridium difficile found in liquid stool samples of hospitalized patient, and the possibility of asymptomatic carriage in 2% of patients with formed stool.

Bacterial enteritis in dogs and cats: diagnosis, therapy, and zoonotic potential

A variety of bacteria are known or suspected of being able to cause enteritis in dogs and cats. Campylobacter spp, Clostridium difficile, Clostridium perfringens, and Salmonella spp are most commonly implicated, but many other organisms are likely involved. Poor understanding of the intestinal microflora and the fact that many, if not all, of these microorganisms can also be found in healthy individuals complicates testing, thereby affecting the use of specific treatments and assessment of potential infection control and zoonotic disease risks. An understanding of the strengths and limitations of various diagnostic options is important for the management of canine and feline enteritis.

Evaluation of in vitro properties of di-tri-octahedral smectite on clostridial toxins and growth

REASONS FOR PERFORMING STUDY

Clostridial colitis and endotoxaemia of intestinal origin are significant causes of morbidity and mortality in horses. Intestinal adsorbents are available for treatment of these conditions; however, little information exists supporting their use.

OBJECTIVES

To evaluate the ability of di-tri-octahedral smectite to bind to Clostridium difficile toxins A and B, C. perfringens enterotoxin and endotoxin, inhibit clostridial growth and the actions of metronidazole in vitro.

METHODS

Clostridium difficile toxins, C. perfringens enterotoxin and endotoxin were mixed with serial dilutions of di-tri-octahedral smectite, then tested for the presence of clostridial toxins or endotoxin using commercial tests. Serial dilutions of smectite were tested for the ability to inhibit growth of C. perfringens in culture broth, and to interfere with the effect of metronidazole on growth of C. perfringens in culture broth.

RESULTS

Clostridium difficile toxins A and B, and C. perfringens enterotoxin were completely bound at dilutions of 1:2 to 1:16. Partial binding of C. difficile toxins occurred at dilutions up to 1:256 while partial binding of C. perfringens enterotoxin occurred up to a dilution of 1:128. Greater than 99% binding of endotoxin occurred with dilutions 1:2 to 1:32. No inhibition of growth of C. difficile or C. perfringens was present at any dilution, and there was no effect on the action of metronidazole.

CONCLUSIONS

Di-tri-octahedral smectite possesses the ability to bind C. difficile toxins A and B, C. perfringens enterotoxin and endotoxin in vivo while having no effect on bacterial growth or the action of metronidazole.

POTENTIAL RELEVANCE

In vivo studies are required to determine whether di-tri-octahedral smectite might be a useful adjunctive treatment of clostridial colitis and endotoxaemia in horses.

C. Diff Quik Chek complete enzyme immunoassay provides a reliable first-line method for detection of Clostridium difficile in stool specimens

We evaluated a single membrane device assay for simultaneously detecting both Clostridium difficile glutamate dehydrogenase (GDH) and toxin A/B antigens against a standard that combines two PCR assays and cytotoxigenic culture. Results showing dual GDH and toxin A/B antigen positives and negatives can be reported immediately as true positives and negatives, respectively. Specimens with discrepant results for GDH and toxins A/B, which comprised 13.2% of the specimens, need to be retested.

[Clostridium difficile TOX A/B II TEST evaluation]

We compared the performance of two commercial toxin detection kits, C. difficile toxin A/B (C. difficile TOX A/B II test; TOX A/B II) and C. difficile toxin A (Uniquick), for (i) detection using highly purified toxin A solution; (ii) cross-reactivity using culture supernatants of toxin A-positive and B-positive C. difficile, toxin A-negative and B-positive C. difficile, and toxin A-negative and B-negative C. difficile strains and other bacteria; and (iii) sensitivity and specificity using clinical specimens. Results indicated that TOX A/B II detected toxin A at concentrations of 0.35 ng/mL and Uniquick at concentrations of 0.7 ng/mL. Uniquick performance was specific for detecting toxin A alone, while TOX A/B II detected toxin A/B specifically. Kit performance was then evaluated using 99 fecal specimens--43 specimens from patients with toxin B-positive C. difficile and 56 from those without. Sensitivity of TOX A/B II vs Uniquick was 95.3% vs 76.7%, specificity 98.2% vs 98.2%, positive predictive 97.6% vs 97.1%, and negative predictive value 96.5% vs 84.6%. Findings thus indicate that TOX A/B II is a more suitable diagnostic aid for CDAD than Uniquick because it correlates well with toxin B-positive C. difficile culture results. Stool culture for C. difficile is also required, however.

[Comparison of two enzyme immunoassay for detection of Clostridium difficile toxin A and toxin B]

BACKGROUND

Enzyme immunoassay (EIA) capable of detecting both toxin A and toxin B is strongly recommended for the diagnosis of Clostridium difficile associated disease. Therefore, we evaluated two different EIAs for the detection of C. difficile toxin A/B.

METHODS

For a total of 228 stool specimens we performed bacteriologic cultures for C. difficile and examined for toxin A and toxin B using enzyme linked fluorescent immunoassay (ELFA; VIDAS CDAB, Bio-Merieux sa, France) and ELISA (C.DIFFICILE TOX A/B II, TECHLAB, USA). We also performed PCR assays for toxin A and B genes in 117 C. difficile isolates that grew from the stool cultures and compared the results with those obtained with the two different EIAs.

RESULTS

The concordance rate between ELFA and ELISA was 85.5% (195/228). Using the culture and PCR results as the standard, the sensitivity/specificity of the ELFA and ELISA were 65.0%/72.1% and 71.8%/70.3%, and for positive/negative predictive values were 78.4%/69.6% and 71.8%/70.3%, respectively (P value >0.05). No differences were observed between the results of ELFA and ELISA with toxin A(-) toxin B(+) strains of C. difficile.

CONCLUSIONS

The sensitivity of the ELISA was slightly higher than that of ELFA for toxin A and toxin B, but the specificity and positive predictive value of the ELFA were rather higher than those of the ELISA, although no statistical differences were observed. A bacteriologic culture and PCR assay for toxin genes are recommended in case the both EIAs are negative.

Algorithm combining toxin immunoassay and stool culture for diagnosis of Clostridium difficile infection

Enzyme immunoassays (EIA) to detect glutamate dehydrogenase or toxins A (TcdA) and B (TcdB), a cytotoxicity assay, and bacteriologic culture have disadvantages when applied individually to diagnosis of Clostridium difficile infections. Stool specimens (n = 1,596) were subjected to toxin detection via an enzyme-linked fluorescent immunoassay (ELFA; Vidas CDAB assay) and bacteriologic culture for toxigenic C. difficile in a three-step algorithm with additional toxigenic culture. Isolates (n = 163) from ELFA-negative stool specimens were examined via ELFA for toxin production. We amplified tcdA and tcdB from C. difficile isolates and tcdB from stool specimens that were ELFA positive or equivocal and culture negative, and we compared the results to those obtained with the three-step algorithm. More than 26% of stool specimens (419/1,596) were culture positive, yielding 248 isolates (59.2%) with both toxin genes (tcdA- and tcdB-positive isolates), 88 isolates (21.0%) with either tcdA or tcdB, and 83 (19.8%) that had no toxin genes (tcdA- and tcdB-negative isolates). Among 49 (culture-negative/ELFA-positive or -equivocal) stool specimens, 53.1% (26/49) represented tcdB-positive isolates. Therefore, the total number of PCR-positive cases was 362, and 27.1% (98/362) of these were detected through toxigenic culture. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 63.3%, 96.7%, 90.5%, and 92.4% (ELFA alone); 92.8%, 93.3%, 80.2%, and 97.8% (culture); and 70.7%, 91.4%, 95.5%, and 100% (three-step algorithm ELFA and bacterial culture with toxigenic culture), respectively, with culture and PCR for tcdA and tcdB as the standards. Thus, sensitivity and specificity were highest using culture and ELFA, respectively, but we recommend the three-step algorithm comprising EIA to detect both toxins and toxigenic culture for C. difficile as a practical method for achieving better PPV and NPV.

Clostridium difficile infection in solid organ transplant recipients

PURPOSE OF REVIEW

To provide a general understanding of Clostridium difficile infection with a focus on recent publications that evaluate the disease in solid organ transplant recipients.

RECENT FINDINGS

The incidence of C. difficile infection is increasing worldwide. Epidemics due to a hypervirulent C. difficile strain are associated with an escalating severity of disease. New evidence further supports basing initial treatment choice on disease severity.

SUMMARY

C. difficile is a significant pathogen in solid organ transplant recipients. Multiple risk factors are found in this population that may result in more severe disease. A high index of suspicion is necessary for the early diagnosis and treatment of C. difficile infection in transplant recipients. Metronidazole and vancomycin show equivalent efficacy in the treatment for mild-to-moderate disease, but vancomycin has demonstrated superiority in the treatment of severe disease. Surgical intervention is also an important consideration in the treatment of solid organ transplant recipients with severe colitis. Rigorous infection control practices are essential for preventing the spread of C. difficile within the hospital environment.

Trends in Clostridium difficile Disease: Epidemiology and Intervention

Clostridium difficile is the most common cause of nosocomial infectious diarrhea. The incidence of C difficile infection (CDI) is increasing in both inpatients and outpatients, and outbreaks caused by a hypervirulent strain of C difficile are resulting in more severe disease. Moreover, community-associated CDI is occurring in persons who lack the traditional risk factors, which include antibiotic use, advanced age, and severe underlying disease. The clinical severity of CDI ranges from a mild, self-limited diarrheal illness to a fulminant, life-threatening colitis. Enzyme-linked immunosorbent assay is the most common laboratory method used for detection of C difficile toxins and can confirm the diagnosis within several hours. The choice of treatment should be based on disease severity. Oral metronidazole is generally regarded as the treatment of choice for mild to moderate CDI, while oral vancomycin is recommended for severe disease. Timely surgical intervention is important in patients who have severe complicated CDI.

Evaluation of enzyme immunoassays to detect Clostridium difficile toxin from anaerobic stool culture

Stool culture for Clostridium difficile, while necessary for strain typing and antimicrobial surveillance, cannot determine toxin production. We prospectively tested in triplicate 91 C difficile cultured isolates for toxin production by 2 enzyme immunoassays (EIAs) (Meridian Premier Toxins A&B, Meridian Bioscience, Cincinnati, OH; and TechLab Tox A/B II, TechLab, Blacksburg, VA) and cytotoxin neutralization bioassay (CTN). By CTN, 88% (80/91) were toxigenic. Reproducibility was 93% (85/91) for CTN, 80% (73/91) for Meridian EIA, and 79% (72/91) for TechLab EIA. Compared with CTN, sensitivities were 87.1% and 89.2% for the Meridian and TechLab EIAs, respectively. In an additional 115 stool specimens, CTN detected toxin more frequently from cultured isolates (96/115) than stool (84/115). For C difficile toxin detection from isolates, EIA was less reproducible than CTN. EIA methods can be falsely negative in 10% to 12% of isolates, and these should be tested by CTN or polymerase chain reaction. When positive, EIA is fast and reliable for detecting C difficile toxin from culture.

Comparison of a commercial real-time PCR assay for tcdB detection to a cell culture cytotoxicity assay and toxigenic culture for direct detection of toxin-producing Clostridium difficile in clinical samples

Rapid detection of toxin-producing strains of Clostridium difficile is essential for optimal management of patients with C. difficile infection. The BD GeneOhm (San Diego, CA) Cdiff assay, a real-time PCR assay that amplifies tcdB, was compared to a cell culture neutralization assay (Wampole C. difficile Toxin B [TOX-B] test; TechLab, Blacksburg, VA) and to toxigenic culture. Using liquid (n = 273) and soft (n = 131) stool specimens from 377 symptomatic patients, all testing was performed on the same day by independent laboratory staff according to the manufacturers' protocols. Toxigenic bacterial culture was performed as follows. A 0.5-ml aliquot of stool was heated to 80 degrees C for 10 min, followed by inoculation onto modified cycloserine cefoxitin fructose agar with and without horse blood (Remel, Lenexa, KS) and into prereduced chopped-meat broth. Of the 404 stool specimens tested, 340 were negative and 40 were positive (10.0% prevalence) both by PCR for tcdB and by cytotoxin production. The overall agreement between the BD GeneOhm Cdiff assay and the TOX-B test was 94.8% (380/401). When the TOX-B test was used as the reference method, the initial sensitivity, specificity, and positive and negative predictive values of the BD GeneOhm Cdiff assay were 90.9% (40/44), 95.2% (340/357), 70.2% (40/57), and 98.8% (340/344), respectively. When toxigenic culture was used as the "gold standard," the sensitivity, specificity, and positive and negative predictive values of the BD GeneOhm Cdiff assay were 83.6%, 98.2%, 89.5%, and 97.1%, respectively, and those of the TOX-B test were 67.2%, 99.1%, 93.2%, and 94.4%, respectively. PCRs for three samples were inhibited upon initial testing; one sample was resolved upon retesting. One sample produced nonspecific cytotoxin results. The BD GeneOhm Cdiff assay performed well compared to a standard cell culture neutralization assay and to toxigenic culture for the detection of toxigenic C. difficile directly from fecal specimens.

Clinical review of the management of fulminant clostridium difficile infection

BACKGROUND

Clostridium difficile infection (CDI) is a frequent cause of morbidity and mortality among elderly hospitalized patients. A small but increasing number of patients have developed fulminant CDI, and a significant number of these patients require emergency colectomy. In this review, we discuss the risk factors, pathophysiology, diagnosis, and management of fulminant CDI.

DATA SOURCES

A literature search (Medline, Embase, Cochrane Library, Biosis, Science Citation Index, Ovid Journals) was performed from the period between January 1980 and June 2008 using the key words "Clostridium difficile,""pseudomembranous enterocolitis,""colectomy,""acute abdomen,""antibiotic-associated diarrhea," or "fulminant Clostridium difficile colitis." Articles not in English or not related to human subjects were excluded. For this review, we analyzed the articles identified in our original search and those articles cited in the original review articles. No randomized trials were found on the surgical management of fulminant CDI and only retrospective studies with a minimum of five patients were used in the review. With respect to medical treatment, we based our review on guideline articles, systematic reviews, and available randomized trials.

CONCLUSION

Both the incidence and severity of CDI are increasing. Fulminant CDI is underappreciated as a life-threatening disease because of a lack of awareness of its severity and its nonspecific clinical syndrome. Early diagnosis and treatment are essential for a good outcome, and early surgical intervention should be used in patients who are unresponsive to medical therapy. The surgical procedure of choice is a total abdominal colectomy with end ileostomy, although the mortality rate remains high.

Multicentre study of the prevalence of toxigenic Clostridium difficile in Korea: results of a retrospective study 2000-2005

The prevalence of toxigenic Clostridium difficile in Korea has been reported to be approximately 60-80%. Although the prevalence of the tcdA(-)tcdB(+) C. difficile strain was less then 5% prior to the year 2000, it has become an emerging nosocomial pathogen in Korea. Therefore, we have attempted to determine the multicentre nationwide prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile for epidemiological purposes. C. difficile strains (n=724, 30 from 2000, 80 from 2001, 74 from 2002, 76 from 2003, 179 from 2004, 285 from 2005) were obtained retrospectively from January 2000 to December 2005 from in-patients at 6 hospitals, all of whom were suspected of having C. difficile-associated disease (CDAD), colitis or pseudomembranous colitis. The numbers of participating hospitals varied yearly (1 in 2000, 2 in 2001-2003, 3 in 2004, 5 in 2005). The hospitals were located in Seoul (n=4), Kyunggi Province (n=1) and Busan (n=1), Korea. PCR assays for tcdA and tcdB genes were conducted using 724 unduplicated C. difficile isolates. The mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains over the 6 years was 51.8 % (38.4-59.3%) and 25.8%(10-56.0%), respectively. The mean prevalence of tcdA(-)tcdB(+) C. difficile strains was less than 7% until 2002, but began to increase in 2003 (13.2%) and achieved a peak in 2004 (50.3%). In 2005, the mean prevalence of tcdA(+)tcdB(+) and tcdA(-)tcdB(+) C. difficile strains was 47.7% (30.9-60.3%) and 27.0% (17.6-54.8%), respectively. This nationwide epidemiological study showed that tcdA(-)tcdB(+) C. difficile strains have already spread extensively throughout Korea, and our results provide basic data regarding the controversies currently surrounding the toxigenicity of tcdA(-)tcdB(+) C. difficile. The use of enzyme immunoassays capable of detecting both TcdA and TcdB is strongly recommended for the diagnosis of CDAD in microbiology laboratories, in order to control the spread of the tcdA(-)tcdB(+) strains of C. difficile.

Evaluation of two rapid immunochromatography tests for the detection of Clostridium difficile toxins

The aim of the study was to evaluate the performance of two rapid immunochromatography tests, the Tox A/B Quick Chek (TechLab) and the ImmunoCard Toxins A&B test (Meridian), in addition to the older Tox A/B ELISA, against PCR detection of the tcdB gene. Two hundred patient-unique stool specimens were tested. In comparison to the polymerase chain reaction results, the sensitivity and specificity of the two rapid tests were 94.7% and 97.2%, respectively; corresponding values for the ELISA were 93.6% and 94.3%. Findings on the rapid tests showed a 96% correlation with polymerase chain reaction assay and a 94% correlation with ELISA. Considering the importance of early and appropriate diagnosis of Clostridium difficile-associated diarrhea, rapid immunochromatography tests may be of great benefit to practitioners.

Diarrheal diseases in the elderly

Diarrhea in the elderly population is one disease that needs special attention in treatment and management, especially in acute- and long-term care residents, because of their multiple comorbidities, immunosenescence, frailty, and poor nutritional status. Close follow-up to ensure adequate hydration and electrolyte replacement and infection control measures to contain outbreaks should be emphasized to caregivers and nursing staff in acute- and long-term care facilities. Although C difficile colitis causes significant morbidity and mortality in this population, judicious use of antibiotics is important to decrease the incidence and recurrence of the disease. When the diarrhea is chronic and all stool testings and serologies have been performed, the patient may benefit from endoscopy and colonoscopy for biopsy. Attentive and vigilant nursing staff is crucial in the timely diagnosis and treatment of diarrheal diseases to improve quality of life and reduce mortality.

Emerging toxin A-B+ variant strain of Clostridium difficile responsible for pseudomembranous colitis at a tertiary care hospital in Korea

Sixty percent to 80% of Clostridium difficile isolates in Korea have been reported to be toxigenic. However, over 1 year, we encountered a high number of tcdA-tcB+ strains associated with pseudomembranous colitis (PMC). C. difficile was isolated from 224 of 471 specimens (47.6%) from 371 patients. A subset of the culture-positive specimens (n = 106), containing no duplicate cases, was randomly selected for tcdA and tcdB polymerase chain reaction (PCR) assays. PCR results showed that tcdA+tcdB+ and tcdA-tcdB+ strains accounted for 39.6% (42/106) and 50.9% (54/106), respectively. Endoscopy, performed on 55/106 patients, revealed 29 with PMC, 5 with colitis, 14 with other colon diseases, and 7 normal cases. Among the 29 PMC cases, 21 (72.4%) were associated with tcdA-tcdB+ strains (P = 0.0016). These results revealed the possible emergence of tcdA-tcdB+ C. difficile strains in Korea, and these variant strains could evoke a higher rate of PMC than tcdA+tcdB+ strains.

Prevalence and risk factors for Clostridium difficile colonization in dogs and cats hospitalized in an intensive care unit

Clostridium difficile is the most common cause of hospital- and antimicrobial-associated diarrhea in hospitalized humans however the role of C. difficile in diarrhea in dogs has not been defined. A prospective study of C. difficile colonization in dogs and cats was conducted in a veterinary teaching hospital intensive care unit (ICU). Rectal swabs were taken from patients upon admission to the ICU and every third day of hospitalization until discharge or death. C. difficile was isolated from 73/402 (18%) animals; 69% of isolates were toxigenic. Community-associated colonization was identified in 39/366 (11%) of animals that were sampled at the time of admission, while C. difficile was subsequently isolated from 27 of the remaining 327 (8.3%) animals that had a negative admission swab. C. difficile was isolated from seven other dogs during hospitalization, but the origin was unclear because the admission swab was not collected. Administration of antimicrobials prior to admission and administration of immunosuppressive drugs during hospitalization were risk factors for hospital-associated colonization (P=0.006, OR 4.05, 95% CI 1.4-10.8). Acquisition of C. difficile during hospitalization in the ICU was associated with the development of diarrhea (P=0.004). Two ribotypes, one toxigenic and one non-toxigenic, predominated.

Epidemiology of Clostridium difficile infection in a large teaching hospital in Singapore

AIMS

We undertook this study to define the incidence of toxigenic Clostridium difficile in our hospital and to characterise the isolates.

METHODS

All unformed stool was tested for the presence of Toxin A (TcdA) and Toxin B (TcdB), and cultured for C. difficile. Culture filtrates were also tested for TcdA and TcdB. Detection of tcdA and tcdB genes was carried out for A(-)B(+) strains by polymerase chain reaction (PCR).The minimum inhibitory concentrations (MICs) of metronidazole, vancomycin and clindamycin for all isolates were tested using the Etest. PCR ribotyping was carried out on all isolates.

RESULTS

The incidence of Clostridium difficile associated disease (CDAD) was 3.2 cases per 1000 admissions or discharges and 53.8 cases per 100 000 patient days. Most cases occurred in renal and haematology patients. CDAD was more common in patients aged over 50 years and of male gender. The Indian population was under-represented. Fourteen (11.8%) isolates were A(-)B(+). All strains were susceptible to metronidazole but one strain showed intermediate resistance to vancomycin. Only 12.8% of the isolates were susceptible to clindamycin. Thirty-five isolates had PCR ribotype A, of which 29 (83%) had a clindamycin MIC >256 mg/L. Thirty-three had PCR ribotype B, of which only one (3%) had a clindamycin MIC >256 mg/L. The 14 A(-)B(+) strains were all PCR ribotype C, and had a range of MICs for clindamycin from 2 to >256 mg/L.

CONCLUSIONS

The incidence of CDAD in our hospital is relatively low. Isolates remain susceptible to metronidazole and vancomycin.

Detection of Clostridium difficile toxin: comparison of enzyme immunoassay results with results obtained by cytotoxicity assay

Several kinds of laboratory techniques are available to detect Clostridium difficile toxin in fecal samples. Because questions have been raised about the reliability of immunoassays compared to the accepted standard, cytotoxicity assay, we studied three enzyme immunoassays (EIAs) and one rapid EIA, which demonstrated relatively good sensitivities and specificities compared to cytotoxicity assay.

Molecular characterization and antimicrobial susceptibilities of extra-intestinal Clostridium difficile isolates

Amongst 25 extra-intestinal clinical isolates of Clostridium difficile, A(+)B(+) (72%) and A(-)B(+) (4%) toxigenic phenotypes, as well as the non-toxigenic phenotype (A(-)B(-)) (24%), were identified. The A(-)B(-) isolates did not express toxin, yet carried part of the tcdA and tcdB gene and are of a previously unreported toxinotype. Six A(+)B(+) isolates also carried binary toxin genes. Resistance to erythromycin (20%), clindamycin (48%), tetracycline (16%), moxifloxacin (16%) and imipenem (11%) occurred but with no apparent correlation to phenotype. None of the strains was resistant to vancomycin or metronidazole. Imipenem-resistance decreased by EDTA, but susceptibility to meropenem suggests the presence of an imipenem specific metalloenzyme.

Isolation and characterisation of toxin A-negative, toxin B-positive Clostridium difficile in Dublin, Ireland

Clostridium difficile is a major cause of infectious diarrhoea in hospitalised patients. Most pathogenic C. difficile strains produce two toxins, A and B; however, clinically relevant toxin A-negative, toxin B-positive (A- B+) strains of C. difficile that cause diarrhoea and colitis in humans have been isolated worldwide. The aims of this study were to isolate and characterise A- B+ strains from two university hospitals in Dublin, Ireland. Samples positive for C. difficile were identified daily by review of ELISA results and were cultured on selective media. Following culture, toxin-specific immunoassays, IMR-90 cytotoxicity assays and PCR were used to analyse consecutive C. difficile isolates from 93 patients. Using a toxin A-specific ELISA, 52 samples produced detectable toxin. All isolates were positive using a toxin A/B ELISA. Similarly, all isolates were positive with the cytoxicity assay, although variant cytopathic effects were observed in 41 cases. PCR amplification of the toxin A and toxin B genes revealed that 41 of the previous A- B+ strains had a c. 1.7-kb deletion in the 3'-end of the tcdA gene. Restriction enzyme analysis of these amplicons revealed the loss of polymorphic restriction sites. These 41 A- B+ isolates were designated toxinotype VIII by comparison with C. difficile strain 1470. PCR ribotyping revealed that all A- B+ isolates belonged to PCR-ribotype 017. A- B+ C. difficile isolates accounted for 44% of the isolates examined in this study, and appeared to be isolated more frequently in Dublin, Ireland, than reported rates for other countries.

Clostridium difficile PCR ribotypes in calves, Canada

C. difficile, including epidemic PCR ribotypes 017 and 027, were isolated from dairy calves in Canada.

We investigated Clostridium difficile in calves and the similarity between bovine and human C. difficile PCR ribotypes by conducting a case-control study of calves from 102 dairy farms in Canada. Fecal samples from 144 calves with diarrhea and 134 control calves were cultured for C. difficile and tested with an ELISA for C. difficile toxins A and B. C. difficile was isolated from 31 of 278 calves: 11 (7.6%) of 144 with diarrhea and 20 (14.9%) of 134 controls (p = 0.009). Toxins were detected in calf feces from 58 (56.8%) of 102 farms, 57 (39.6%) of 144 calves with diarrhea, and 28 (20.9%) of 134 controls (p = 0.0002). PCR ribotyping of 31 isolates showed 8 distinct patterns; 7 have been identified in humans, 2 of which have been associated with outbreaks of severe disease (PCR types 017 and 027). C. difficile may be associated with calf diarrhea, and cattle may be reservoirs of C. difficile for humans.

Evaluation of three rapid assays for detection of Clostridium difficile toxin A and toxin B in stool specimens

Diagnosis of Clostridium difficile-associated disease continues to be difficult for clinical microbiology laboratories. The aim of this study was to evaluate the performance of three enzyme immunoassays for detection of C. difficile toxins A and B: the recently marketed rapid enzyme immunoassay Ridascreen Clostridium difficile Toxin A/B (R-Biopharm, Darmstadt, Germany) and two established enzyme immunoassays, the C. difficile Tox A/B II Assay (TechLab, Blacksburg, VA, USA) and the ProSpecT C. difficile Toxin A/B Microplate Assay (Remel, Lenexa, KS, USA). Stool specimens (n = 383) from patients with a clinical diagnosis of antibiotic-associated diarrhea were examined by these three enzyme immunoassays and were additionally cultured for C. difficile on selective agar. Samples giving discordant enzyme immunoassay results underwent confirmatory testing by tissue culture cytotoxin B assay and by PCR for toxin A (tcdA) and toxin B (tcdB) genes from C. difficile. Using the criteria adopted for this study, 60 (15.7%) samples tested positive for toxins A and/or B. Sensitivity and specificity of the enzyme immunoassays were, respectively, 88.3 and 100% for the TechLab enzyme immunoassay, 91.7 and 100% for the R-Biopharm enzyme immunoassay, and 93.3 and 100% for the Remel enzyme immunoassay. The differences between these results are statistically not significant (p > 0.05). The results show that all three enzyme immunoassays are acceptable tests for the detection of C. difficile toxins A and B directly in fecal specimens or in toxigenic cultures.

Toxin A-negative, toxin B-positive Clostridium difficile

Clostridium difficile is a major cause of infectious diarrhea in hospitalized patients. Many pathogenic strains of Clostridium difficile produce two toxins TcdA and TcdB, both of which are pro-inflammatory and enterotoxic in human intestine. Clinically relevant toxin A-negative, toxin B-positive (A(-)B(+)) strains of Clostridium difficile that cause diarrhea and colitis in humans have been isolated with increasing frequency worldwide. This perspective describes these important toxin variant strains and highlights the need to use Clostridium difficile diagnostic methods that can detect both TcdA and TcdB.

Helicobacter pylori and Clostridium difficile in cystic fibrosis patients

We describe the prevalence of H. pylori and toxigenic Clostridium difficile (CD) infection and its relationship with gastrointestinal symptoms and pancreatic sufficiency (PS) or insufficiency (PI) in cystic fibrosis (CF) patients. Stool specimens from 30 consecutive patients with CF, aged 1-44, and from 30 healthy similarly aged subjects were tested for the H. pylori antigen by specific monoclonal antibodies and for CD toxins by Tox A/B assay and Tox A assay. CF patients were assessed clinically and tested for specific H. pylori serum antibodies and for mutations. In CF patients, the prevalence of H. pylori antigen was 16.6% (5/30), compared to 30% (9/30) in controls. Of the 26 CF patients with PI, only 2 (7.6%) were infected by H. pylori, compared with 3 of the 4 (75%) patients with PS (P=0.001). H. pylori infection was diagnosed in 3 of 5 (60%) CF patients carrying mild mutations, compared to 1 of 25 (4%) CF patients carrying severe mutations (P=0.01). Fourteen of 30 (46.6%) stool specimens from CF patients tested positive in the ToxA/B assay, and 3 of 14 tested positive for ToxA. No significant differences in antibiotic use, severity of lung disease, PI, chronic abdominal pain, or genotype were found between the two groups. None of the controls was positive for CD toxins. Prevalence of H. pylori infection in CF patients was lower than in similarly aged non-CF controls. CF patients with PI or a history of distal intestinal obstruction syndrome and those carrying mutations associated with a severe phenotype were protected against H. pylori infection. Almost half of the CF patients were asymptomatic carriers of CD producing mostly toxin B. More studies are needed to confirm our results in a larger group of CF patients.

Effective detection of toxigenic Clostridium difficile by a two-step algorithm including tests for antigen and cytotoxin

We evaluated a two-step algorithm for detecting toxigenic Clostridium difficile: an enzyme immunoassay for glutamate dehydrogenase antigen (Ag-EIA) and then, for antigen-positive specimens, a concurrent cell culture cytotoxicity neutralization assay (CCNA). Antigen-negative results were > or = 99% predictive of CCNA negativity. Because the Ag-EIA reduced cell culture workload by approximately 75 to 80% and two-step testing was complete in < or = 3 days, we decided that this algorithm would be effective. Over 6 months, our laboratories' expenses were US dollar 143,000 less than if CCNA alone had been performed on all 5,887 specimens.

An update on diagnosis, treatment, and prevention of Clostridium difficile-associated disease

Clostridium difficile is an important cause of nosocomial morbidity and mortality and is implicated in recent epidemics. Data support the treatment of colitis with oral metronidazole in a dose of 1.0 to 1.5 g/d, with oral vancomycin as a second-line agent, not because its efficacy is questioned but because of environmental concerns. Nitazoxanide and other drugs are currently under intense study as alternatives. Treatment of asymptomatic patients is not recommended. Current management strategies appear to be increasingly ineffective, especially for patients who experience multiple recurrences. Biotherapy and vaccination are currently being explored as treatment options for patients who have recurrent disease. Greater attention should be paid to hospital infection control policies and restriction of broad-spectrum antibiotics.

Rapid and simple method for detecting the toxin B gene of Clostridium difficile in stool specimens by loop-mediated isothermal amplification

We applied the loop-mediated isothermal amplification (LAMP) assay to the detection of the toxin B gene (tcdB) of Clostridium difficile for identification of toxin B (TcdB)-positive C. difficile strains and detection of tcdB in stool specimens. tcdB was detected in all toxin A (TcdA)-positive, TcdB-positive (A(+)B(+)) and TcdA-negative, TcdB-positive (A(-)B(+)) C. difficile strains but not from TcdA-negative, TcdB-negative strains. Of the 74 stool specimens examined, A(+)B(+) or A(-)B(+) C. difficile was recovered from 39 specimens, of which 38 specimens were LAMP positive and one was negative. Amplification was obtained in 10 specimens that were culture negative, indicating that LAMP is highly sensitive. The LAMP assay was applied to detection of tcdB in DNA extracted by a simple boiling method from 47 of those 74 specimens, which were cultured overnight in cooked-meat medium (CMM). Twenty-two of 24 culture-positive specimens were positive for LAMP on DNA from the culture in CMM. Four specimens were culture negative but positive by LAMP on DNA from CMM cultures. The LAMP assay is a reliable tool for identification of TcdB-positive C. difficile as well as for direct detection of tcdB in stool specimens with high sensitivity. Detection of tcdB by LAMP from overnight cultures in CMM could be an alternative method of diagnostic testing at clinical laboratories without special apparatus.

Multilocus sequence analysis and comparative evolution of virulence-associated genes and housekeeping genes of Clostridium difficile

A multilocus sequence analysis of ten virulence-associated genes was performed to study the genetic relationships between 29 Clostridium difficile isolates of various origins, hosts and clinical presentations, and selected from the main lineages previously defined by multilocus sequence typing (MLST) of housekeeping genes. Colonization-factor-encoding genes (cwp66, cwp84, fbp68, fliC, fliD, groEL and slpA), toxin A and B genes (tcdA and tcdB), and the toxin A and B positive regulator gene (tcdD) were investigated. Binary toxin genes (cdtA and cdtB) were also detected, and internal fragments were sequenced for positive isolates. Virulence-associated genes exhibited a moderate polymorphism, comparable to the polymorphism of housekeeping genes, whereas cwp66 and slpA genes appeared highly polymorphic. Isolates recovered from human pseudomembranous colitis cases did not define a specific lineage. The presence of binary toxin genes, detected in five of the 29 isolates (17 %), was also not linked to clinical presentation. Conversely, toxigenic A−B+ isolates defined a very homogeneous lineage, which is distantly related to other isolates. By clustering analysis, animal isolates were intermixed with human isolates. Multilocus sequence analysis of virulence-associated genes is consistent with a clonal population structure for C. difficile and with the lack of host specificity. The data suggest a co-evolution of several of the virulence-associated genes studied (including toxins A and B and the binary toxin genes) with housekeeping genes, reflecting the genetic background of C. difficile, whereas flagellin, cwp66 and slpA genes may undergo recombination events and/or environmental selective pressure.

Clostridium difficile: an update

Clostridium difficile causes a spectrum of diarrheal illness with the potential for major medical consequences. Although most cases respond quickly to treatment, C. difficile colitis may be severe and life threatening. Recurrent disease represents a particularly challenging problem.

Multiplex PCR targeting tpi (triose phosphate isomerase), tcdA (Toxin A), and tcdB (Toxin B) genes for toxigenic culture of Clostridium difficile

A multiplex PCR toxigenic culture approach was designed for simultaneous identification and toxigenic type characterization of Clostridium difficile isolates. Three pairs of primers were designed for the amplification of (i) a species-specific internal fragment of the tpi (triose phosphate isomerase) gene, (ii) an internal fragment of the tcdB (toxin B) gene, and (iii) an internal fragment of the tcdA (toxin A) gene allowing distinction between toxin A-positive, toxin B-positive (A+B+) strains and toxin A-negative, toxin B-positive (A-B+) variant strains. The reliability of the multiplex PCR was established by using a panel of 72 C. difficile strains including A+B+, A-B-, and A-B+ toxigenic types and 11 other Clostridium species type strains. The multiplex PCR assay was then included in a toxigenic culture approach for the detection, identification, and toxigenic type characterization of C. difficile in 1,343 consecutive human and animal stool samples. Overall, 111 (15.4%) of 721 human samples were positive for C. difficile; 67 (60.4%) of these samples contained A+B+ toxigenic isolates, and none of them contained A-B+ variant strains. Fifty (8%) of 622 animal samples contained C. difficile strains, which were toxigenic in 27 (54%) cases, including 1 A-B+ variant isolate. Eighty of the 721 human stool samples (37 positive and 43 negative for C. difficile culture) were comparatively tested by Premier Toxins A&B (Meridian Bioscience) and Triage C. difficile Panel (Biosite) immunoassays, the results of which were found concordant with toxigenic culture for 82.5 and 92.5% of the samples, respectively. The multiplex PCR toxigenic culture scheme described here allows combined diagnosis and toxigenic type characterization for human and animal C. difficile intestinal infections.

Clostridium difficile-associated colitis

OBJECTIVE

To review the basic microbiology, pathogenesis of disease, and diagnosis of the nosocomial pathogen Clostridium difficile and to examine therapies recommended by the Canadian Task Force on Preventive Health Care. QUALITY OF EVIDENCE MEDLINE: was searched using MeSH headings. Controlled trials for therapy were sought, but case-control studies and observational reviews were included.

MAIN MESSAGE

Clostridium difficile causes approximately 20% of cases of diarrhea associated with antibiotics, including clindamycin and the second- and third-generation cephalosporins. Diarrhea is usually mild, but can be severe; extreme cases develop toxic megacolon. Diagnosis is dependent on demonstrating presence of clostridial toxin in stool specimens or of pseudomembranes through sigmoidoscopy. First-line therapy for C. difficile diarrhea is restricted to metronidazole. Second-line therapy for treatment failure is vancomycin. For relapse, a second course of metronidazole is recommended; tapering courses of vancomycin and probiotics are used for multiple recurrences.

CONCLUSION

Clostridium difficile is an important nosocomial pathogen requiring prudent use of antibiotics and strict infection-control policies to prevent large health care costs.

Distribution of Clostridium difficile variant toxinotypes and strains with binary toxin genes among clinical isolates in an American hospital

Genetic variants of Clostridium difficile have been reported with increasing frequency, but their true incidence is unknown. C. difficile strains have been classified into variant toxinotypes according to variations in the pathogenicity locus encoding the major virulence factors, toxins A and B. Some strains produce an additional toxin, binary toxin CDT. This survey of clinical isolates (153) from patients in a single hospital set out to ascertain the distribution of variant toxinotypes and strains possessing binary toxin genes. A PCR-RFLP-based method of toxinotyping identified 123 (80.4 %) isolates as toxinotype 0, 13 (8.5 %) strains as non-toxigenic and 17 (11.1 %) as belonging to variant toxinotypes. Binary toxin genes were amplified by PCR in nine strains (5.8 %), all of which were variant toxinotypes. Toxin variants of C. difficile are pathogenic and commonly isolated and need to be considered when evaluating new diagnostic testing strategies for C. difficile disease.

Multilocus sequence typing analysis of human and animal Clostridium difficile isolates of various toxigenic types

A multilocus sequence typing (MLST) scheme was developed to study the genetic relationships and population structure of 72 Clostridium difficile isolates from various hosts, geographic sources, PCR ribotypes, and toxigenic types (determined by PCR targeting tcdA and tcdB genes). MLST was performed by DNA sequence analysis of seven housekeeping genes (aroE, ddl, dutA, tpi, recA, gmk, and sodA). The number of alleles ranged from five (dutA and ddl) to eleven (recA). Allelic profiles allowed the definition of 34 different sequence types (STs). These STs lacked correlation with geographic source but were well correlated to toxigenic type. The dendrogram generated from a matrix of pairwise genetic distances showed that animal isolates did not constitute a distinct lineage from human isolates and that there was no hypervirulent lineage within the population of toxigenic human isolates (isolates recovered from pseudomembranous colitis and antibiotic-associated diarrhea did not cluster in distinct lineages). However, A(-) B(+) variant isolates shared the same ST that appeared as a divergent lineage in the population studied, indicating a single evolutionary origin. The population structure was further examined by analysis of allelic polymorphism. The dendrogram generated from composite sequence-based analysis revealed a homogeneous population associated with three divergent lineages, one of which was restricted to A(-) B(+) variant isolates. C. difficile exhibited a clonal population structure, as revealed by the estimation of linkage disequilibrium (Ia) between loci. The analysis of alleles within clonal complexes estimated that point mutation generated new alleles at a frequency eightfold higher than recombinational exchange, and the congruence of the dendrograms generated from separate housekeeping loci confirmed the mutational evolution of this species.

Antibiotic prescribing policy and Clostridium difficile diarrhoea

BACKGROUND

Broad-spectrum antibiotics, particularly intravenous cephalosporins, are associated with Clostridium difficile diarrhoea. Diarrhoea due to C. difficile is a growing problem in hospitals, especially among elderly patients.

AIM

To establish whether changing an antibiotic policy with the aim of reducing the use of injectable cephalosporins leads to a reduction in the incidence of C. difficile diarrhoea in elderly patients.

DESIGN

Retrospective analysis.

METHODS

A group of patients who were subject to the new antibiotic policy from the period following July 2000, were compared with patients who were admitted prior to July 2000 and were not subject to the new policy. Infections, antibiotic prescriptions and mortality rates were determined from case notes, and C. difficle diarrhoea rates from microbiological data.

RESULTS

Intravenous cephalosporin use fell from 210 to 28 defined daily doses (p < 0.001) following the change in antibiotic policy, with a corresponding increase in piperacillin-tazobactam (p < 0.001) and moxifloxacin (p < 0.001) use. The new policy led to a significant reduction in C. difficile diarrhoea cases. The relative risk of developing C. difficile infection with the old policy compared to the new policy was 3.24 (95%CI 1.07-9.84, p = 0.03).

DISCUSSION

The antibiotic policy was successfully introduced into an elderly care service. It reduced both intravenous cephalosporin use and C. difficile diarrhoea.

Outbreak of Clostridium difficile-associated disease in a small animal veterinary teaching hospital

An apparent outbreak of enteric disease occurred in dogs and cats at a veterinary teaching hospital. Clostridium difficile Toxin A or B or both were identified in 1 or more fecal samples from 48 of 93 (52%) dogs over a 5‐month period, 30 of which were identified in the 1st 26 days, after which strict infection control measures, including closure to elective cases, were implemented. Affected animals included in‐patients, out‐patients that were housed temporarily in the wards, and resident blood donor dogs. Infection control measures, including partial depopulation, isolation, hospital and yard cleaning, and barrier precautions, were instituted, after which, the incidence of nosocomial diarrhea decreased from 19 cases per 1,000 admissions to 2.5 cases per 1,000 admissions (P <0.001)