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

A 33 basepair oligonucleotide probe, designed from the sequence of theClostridium difficile toxin B gene, was evaluated for its ability to detect toxigenicClostridium 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 ofClostridium difficile toxin A in stool specimens was investigated. In 162 samples tested, a sensitivity of 80 % and a specificity of 98 % were obtained.     

Rapid stool-based diagnosis of Clostridium difficile infection by real-time PCR in a children's hospital

Clostridium difficile is a major cause of nosocomial antibiotic-associated infectious diarrhea and pseudomembranous colitis. Detection of C. difficile by anaerobic bacterial culture and/or cytotoxicity assays has been largely replaced by rapid enzyme immunoassays (EIA). However, due to the lack of sensitivity of stool EIA, we developed a multiplex real-time PCR assay targeting the C. difficile toxin genes tcdA and tcdB. Stool samples from hospitalized pediatric patients suspected of having C. difficile-associated disease were prospectively cultured on cycloserine-cefoxitin-fructose agar following alcohol shock. Six testing modalities were evaluated, including stool EIA, culture EIA, and real-time PCR (tcdA and tcdB) of cultured isolates and stool samples. Real-time PCR detection was performed with tcdA and tcdB gene-specific primers and hydrolysis probes using the LightCycler platforms (Roche Diagnostics, Indianapolis, IN). A total of 157 samples from 96 pediatric patients were analyzed. The sensitivities of stool real-time PCR and stool EIA were 95% and 35%, respectively, with a specificity of 100% for both methods. The lower limit of detection of the stool real-time PCR was 30 CFU/ml of stool sample per reaction for tcdA and tcdB. This study highlights the poor performance of stool toxin EIAs in pediatric settings. Direct detection of C. difficile toxin genes in stool samples by real-time PCR showed sensitivity superior to that of stool and culture EIAs and performance comparable to that of real-time PCR assay of cultured isolates. Real-time PCR of DNA from stool samples is a rapid and cost-effective diagnostic modality for children that should facilitate appropriate patient management and halt the practice of serial testing by EIA.     

Evaluation of three diagnostic methods, including real-time PCR, for detection of Dientamoeba fragilis in stool specimens

Dientamoeba fragilis is a protozoan parasite of humans that infects the mucosa of the large intestine and is associated with gastrointestinal disease. We developed a 5' nuclease (TaqMan)-based real-time PCR assay, targeting the small subunit rRNA gene, for the detection of D. fragilis in human stool specimens and compared its sensitivity and specificity to conventional PCR and microscopic examination by a traditional modified iron-hematoxylin staining procedure. Real-time PCR exhibited 100% sensitivity and specificity.     

Development of a rapid enzyme immunoassay for Clostridium difficile toxin A and its use in the diagnosis of C. difficile-associated disease.

A rapid (2.5 h) direct enzyme immunoassay (EIA) for Clostridium difficile toxin A was developed for clinical use. Specimen centrifugation and filtration were not required. The EIA detected toxin A levels in patient stool as low as 20 pg (2 ng/ml of stool). The test was 5,000 times more sensitive for toxin A than it was for toxin B and did not react with a panel of other bacterial species with the exception of one highly toxigenic strain of Clostridium sordellii. The EIA was compared with the cytotoxin assay, culture of toxigenic C. difficile (toxigenic culture), and latex agglutination by using 313 fresh stool specimens submitted from patients with suspected C. difficile-associated disease. Results read visually and with a plate reader were similar. Sixty-two specimens were positive by one or more tests, but only 22 (35%) were positive by all four laboratory methods. The EIA was 84.1% sensitive and 98.9% specific when it was compared with the cytotoxin assay. The use of toxigenic culture to referee discrepant results (EIA versus cytotoxin assay) showed the EIA sensitivity and specificity to be 95.1 and 99.3%, respectively, with respect to other laboratory methods. Patient charts were reviewed for antibiotic-associated diarrhea on 108 specimens, including all those that were positive by at least one test method. Of 34 patients determined to have C. difficile-associated disease, 29 (85.3%) were positive by EIA, 32 (94.1%) were positive by the cytotoxin assay, 27 (79.4%) were positive by toxigenic culture, and 20 (58.8%) were positive by latex agglutination. Seven patients with antibiotic-associated diarrhea had a positive latex result, but results were negative by EIA, the cytotoxin assay, and toxigenic culture. The EIA demonstrated high specificity and good sensitivity for C. difficile-associated disease cases. The test can be used alone or in combination with the cytotoxin assay or toxigenic culture to provide rapid and sensitive results.     

Rapid and Sensitive Assay for Detection of Enterotoxigenic Bacteroides fragilis

Bacteroides fragilis is an obligatory anaerobic, gram-negative bacterium found among the normal intestinal flora of humans. Enterotoxigenic strains of B. fragilis (ETBF) have been associated with diarrheal diseases in humans and animals. The enterotoxin of ETBF induces fluid changes in ligated intestinal segments and cytotoxic response in HT29/C1 cells. By using a pair of monoclonal antibodies (MAbs; MAb C3 and MAb 4H8) specific for the lipopolysaccharide of B. fragilis, an assay based on immunomagnetic separation (IMS) in combination with PCR (IMS-PCR) was developed. After DNA extraction, a 294-bp fragment was amplified. The specificity of the IMS-PCR assay was evaluated by adding previously isolated and confirmed ETBF strains to normal fecal samples. All fecal samples to which ETBF strains were added were positive, showing a 100% specificity. The spiked fecal samples were also used for evaluation of the sensitivity of the assay. The detection limit was found to be ~50 CFU/g of feces. By this method 10 clinical fecal samples (5 from patients with diarrhea and 5 from healthy controls) were examined. The results of PCR were in accordance with the results of the HT29/C1 cell assay for all samples. The minimum time to retrieval of the final result by the IMS-PCR method is 36 h. The proposed IMS-PCR assay is rapid and sensitive for the direct detection of ETBF in stool samples.     

Development and evaluation of a PCR method for detection of the Clostridium difficile toxin B gene in stool specimens

A PCR assay detecting Clostridium difficile toxin B gene in stool specimens was compared to the cytotoxicity assay as the reference standard for the diagnosis of C. difficile antibiotic-associated diarrhea (CDAD). Overall, 118 stool samples were tested. All of the specimens that were negative by the cytotoxicity assay (59 out of 118) were also negative by the PCR method (specificity of 100%). Of the 59 cytotoxin-positive samples, 54 were PCR positive (sensitivity of 91.5%). This PCR method is promising for rapid diagnosis of CDAD.     

Evaluation of the premier EHEC assay for detection of Shiga toxin-producing Escherichia coli.

An enzyme-linked immunosorbent assay for the detection of Shiga toxins (Premier EHEC assay; Meridian Diagnostics, Inc.) was compared to conventional sorbitol-MacConkey culture for the recovery of enterohemorrhagic Escherichia coli. A total of 74 enteric pathogens, including 8 E. coli O157:H7 isolates, were recovered from 974 stool specimens. Two of these specimens were not tested by Premier assaying due to insufficient sample and are not considered in the data analysis. The Premier EHEC assay detected the 6 evaluable specimens which were culture positive for E. coli O157:H7 and identified an additional 10 specimens as containing Shiga toxin. Seven isolates were recovered from these 10 specimens by an immunoblot assay and were confirmed as toxin producers by a cytotoxin assay. Of these seven, four isolates were serotype O157:H7, one was O26:NM, one was O6:H-, and one was O untypeable:H untypeable. Three specimens contained Shiga toxin by both EHEC immunoassaying and cytotoxin testing; however, no cytotoxin-producing E. coli could be recovered. The sorbitol-MacConkey method had a sensitivity and a specificity of 60 and 100%, respectively, while the Premier EHEC assay had a sensitivity and a specificity of 100 and 99.7%, respectively, for E. coli O157:H7 only. The Premier EHEC assay also detected an additional 20% Shiga toxin-producing E. coli (STEC) that were non-O157:H7. Thus, the Premier EHEC assay is a sensitive and specific method for the detection of all STEC isolates. Routine use would improve the detection of E. coli O157:H7 and allow for determination of the true incidence of STEC other than O157:H7. The presence of blood in the stool and/or the ages of the patients were poor predictors of the presence of STEC. Criteria need to be determined which would allow for the cost-effective incorporation of this assay into the routine screen for enteric pathogens in high-risk individuals, especially children.     

腹泻相关致病菌基因芯片的制备及应用

目的确定引起人类感染性腹泻的11种病原微生物,并制备芯片用于检测门诊腹泻患者粪便标本中的致病菌。方法根据本院2009年1月至2012年12月期间腹泻门诊的粪便病原菌检测数据,采用生物信息学的方法,收集11种病原菌的所有基因序列,设计引物及探针,优化并制备芯片,PCR扩增杂交并对杂交结果进行分析。用该芯片对本院保存的163个肠道致病菌临床分离株进行鉴定来评价芯片的特异性,用芯片来检测掺有不同浓度沙门氏菌的粪便标本评价芯片的灵敏度。同时收集2010年6月至2013年3月在本院就诊的1052份腹泻患者粪便标本,平行进行PCR扩增、细菌培养、基因芯片检测,比较不同检测方法的阳性率。结果成功制备了腹泻相关11种致病菌检测芯片。应用制备的芯片检测了163个临床分离株,准确率达100％。与PCR方法比较,基因芯片检测沙门氏菌的灵敏度达102CFU／ml,比PCR法检测灵敏度高10倍。用该芯片对临床1052份腹泻患者腹泻标本进行检测,与传统的培养法及PCR法比较,有较高的阳性检出率,达36％,比常规细菌培养阳性率高13％（X2=2．28,P〈0．05）,比PCR检出率高4％（X2=5．16,P〉0．05）。结论成功制备11种腹泻相关致病菌基因芯片,能同时对11种腹泻致病菌进行检测,有较好的特异性和灵敏度,有更高的阳性率,可以用于临床检测。     

Multicenter evaluation of four methods for Clostridium difficile detection: ImmunoCard C. difficile, cytotoxin assay, culture, and latex agglutination.

A three-center study was undertaken to compare several test methods for the detection of Clostridium difficile, associated toxin, or related markers by using 927 stool specimens. Methods included direct assay of cytotoxin in stool by tissue culture, C. difficile bacterial culture followed by cytotoxin assay, bacterial culture alone, latex agglutination assay, and the ImmunoCard C. difficile test (Meridian Diagnostics, Inc.). The sensitivities, as determined against direct cytotoxin assay results, of the ImmunoCard C. difficile and latex agglutination assays were 84 and 67%, respectively (92 and 77%, respectively, when adjusted for bacterial culture outcomes). Evaluation for C. difficile-associated disease (CDAD) among 864 patients was based on clinical criteria for antibiotic-associated diarrhea combined with laboratory evidence of toxin or toxin-producing C. difficile in stool specimens. The sensitivity of each test method for screening of CDAD was as follows: bacterial culture, 95%; culture with cytotoxin assay of isolates, 90%; ImmunoCard C. difficile test, 83%; cytotoxin assay 82%; and latex agglutination assay, 67% (P < or = 0.05 versus all other methods). The standard deviations of the test sensitivity statistics between study sites were ranked as follows: cytotoxin assay (+/- 3.1%) < ImmunoCard C. difficile test (+/- 5.7%) < latex agglutination assay (+/- 12.3%) < culture (+/- 24.7%) < culture with cytotoxin assay (+/- 28.0%). The data support the use of the ImmunoCard C. difficile test as an adjunct for the diagnosis of CDAD.     

Detection of enterotoxigenic Bacteroides fragilis by PCR.

Strains of enterotoxigenic Bacteroides fragilis (ETBF) are associated with diarrhea in young farm animals and, at least in particular settings, in children. Enterotoxin production by ETBF is currently detected by a tissue culture assay with HT-29 cells. We have developed a PCR assay based on the detection of the enterotoxin gene to identify ETBF in culture and in stool samples. Overall, 113 bacterial strains were examined, including 3 B. fragilis reference strains, 75 B. fragilis isolates (comprising 40 ETBF isolates), 20 Bacteroides spp. other than B. fragilis, and 15 strains belonging to other genera. Complete agreement was found between the results of the tissue culture assay and those of the PCR for our strains. PCR was also used to detect ETBF directly in fecal samples. Stools from two healthy volunteers were spiked with known numbers of ETBF and were processed by three different methods. A culture method, which required inoculation of the stools on selective plates and the collection of the whole bacterial growth ("sweeps"), was found to be the most sensitive. PCR performed with the plate sweeps yielded amplification products with a detection limit of 10(5) to 10(4) CFU/g of feces. By this method 18 samples of diarrheic stools (10 positive and 8 negative for ETBF) were examined. The results of the PCR were in accordance with the culture results in all cases. The proposed PCR assay represents a diagnostic tool for the rapid identification of ETBF in culture as well as in fecal samples.     

Multicentre Evaluation of a Commercial Test for the Rapid Diagnosis of Clostridium difficile-Mediated Antibiotic-Associated Diarrhoea

 An immunoassay for the detection of Clostridium difficile toxin A in stool samples (Clearview C. DIFF A; Unipath, UK) was evaluated against the cell cytotoxicity assay using 407 stool samples from patients suspected to have, or considered at risk of, antibiotic-associated diarrhoea. Of the samples tested, 98 were positive and 280 were negative by both tests (sensitivity 83.1%, specificity 96.9%). Following resolution of the 29 discrepant results, the sensitivity and specificity of the immunoassay were 91% and 98%, respectively, and the sensitivity for the cell cytotoxicity assay was calculated as 91.5%, with a specificity of 99%. The Clearview C. DIFF A test proved to be a rapid simple assay for the detection of Clostridium difficile toxin A in stool samples. The test was equally suited to single or batch testing, required minimal sample handling, and provided results within 30 min of applying the sample to the test unit.     

Plasmodium falciparum histidine-rich protein 2-based immunocapture diagnostic assay for malaria: cross-reactivity with rheumatoid factors

Recently introduced rapid nonmicroscopic immunocapture assays for the diagnosis of malaria infection are being evaluated for their sensitivity and specificity in various epidemiological settings. A Plasmodium falciparum histidine-rich protein 2 (PfHRP-2)-based assay (ICT) and a Plasmodium-specific lactate dehydrogenase test (OptiMAL) were evaluated for their specificities in different groups of patients who tested negative for malaria infection by microscopy. The patients were selected from different disease groups: rheumatoid arthritis, hepatitis C, toxoplasmosis, schistosomiasis, and hydatid disease. One hundred thirty-three of the 225 patients were positive for rheumatoid factor. Thirty-five of the 133 (26%) rheumatoid factor-positive patients gave a false-positive reaction with the ICT assay, but only 4 of these gave false-positive reactions with the OptiMAL test. Thirty-three of the 35 false-positive specimens became negative when repeat tested with the ICT assay after absorbing out the rheumatoid factor activity. Our study shows that the PfHRP-2-based ICT assay gave a false-positive reaction in 26% of the patients who had rheumatoid factors, but were negative for malaria by microscopy.     

Evaluation of the Clearview Clostridium difficile Toxin A Test and various selective culture media in comparison with the cytotoxin assay for the diagnosis of Clostridium difficile-associated diarrhoea

AIM: Clostridium difficile is the major pathogen associated with nosocomial diarrhoea. We evaluated the performances of a commercially available toxin A enzyme immunoassay (EIA; Clearview C. difficile Toxin A Test), culture and tissue culture cytotoxin assay in the diagnosis of C. difficile-associated diarrhoea. METHODS: Comparative test performance was determined from data obtained from 166 faecal samples. The initial analysis compared the performance of toxin A EIA and culture with that of cytotoxin assay, this being defined as a 'laboratory gold standard'. A second analysis compared the individual performance of the toxin A EIA, culture and cytotoxin assay using a combined clinical and laboratory diagnostic assessment as a 'clinical gold standard'. In a parallel, study three selective culture media were compared. RESULTS: From the initial analysis, the sensitivity and specificity of the methods were, respectively, 84.6 and 65.4% for the toxin A EIA, and 38.5 and 93.5% for culture. From the second analysis, the sensitivity and specificity of the methods were, respectively, 100 and 67.5% for the toxin A EIA, 63.6 and 96.7% for culture and 72.7 and 98.0% for cytotoxin assay. Media containing d-cycloserine 250mg/L and cefoxitin 8mg/L performed best, growing 88.2% of the isolates. CONCLUSION: The toxin A EIA we evaluated had poor specificity in the diagnosis of C. difficile-associated diarrhoea. We conclude that in our laboratory the combination of culture and cytotoxin assay is a preferred approach to the diagnosis of C. difficile-associated diarrhoea.     

Clinical and laboratory evaluation of a real-time PCR for Clostridium difficile toxin A and B genes

Many laboratories use enzyme immunoassays (EIAs) for the diagnosis of Clostridium difficile infection (CDI). More recently, polymerase chain reaction (PCR)-based diagnosis has been described as a sensitive test. Real-time PCR for the detection of C. difficile toxin A and B genes was evaluated. A prospective evaluation was performed on stool samples from 150 hospitalized adult patients and 141 healthy volunteers. PCR was compared to toxigenic culture (TC), direct cytotoxicity test (CTT), ImmunoCard? Toxin A and B (Meridian Bioscience), and enzyme-linked immunosorbent assay (ELISA) (Vidas). The results were correlated with clinical data using a standardized questionnaire. The diagnostic yield of the PCR was further evaluated after implementation. Using toxigenic culture as the gold standard, the sensitivity and specificity of PCR were 100 and 99.2%, respectively. Patients were categorized as follows: TC/PCR-positive (n?=?17) and negative TC (n?=?133). The differences in these groups were more frequent use of antibiotics and leukocytosis (p?相似文献   

Comparison of the Oxoid Clostridium difficile toxin A detection kit with cytotoxin detection by a cytopathic effect method examined at 4, 6, 24 and 48 h

Objective: To evaluate the Oxoid Toxin A test in comparison with a rapid cytotoxin method for the diagnosis of Clostridium difficile diarrhea in a UK tertiary referral hospital.
Methods: One hundred previously tested samples were examined using a cytopathic effect (CPE) method and the Oxoid Toxin A test. Culture and toxin B titer measurement of the samples were performed to evaluate discrepancies between the tests.
Results: The sensitivity and specificity of the Oxoid Toxin A test were 72% and 94%, respectively. This was similar to the CPE method read at 6 h: 67% and 94% in comparison. At 48 h, the sensitivity and specificity of the CPE method reached 98% and 100%. Toxigenic strains of C. difficile were cultured from 58 of 100 samples, and toxin was detected in 48 of 58. Following 4 weeks of storage at -20°C, seven of 47 previously toxin B-positive stool filtrates had no detectable toxin.
Conclusions: The Oxoid Toxin A test does not demonstrate a high enough sensitivity and specificity to be used as a primary test for C. difficile in hospitals where CPE testing is possible. Toxigenic strains of C. difficile can be cultured from a significant number of samples where no toxins are detected. Toxin B titers in fecal samples and especially in stool filtrates, stored at -20°C, diminish after thawing.     

Detection of Chlamydia trachomatis in endocervical specimens by polymerase chain reaction.

A rapid and sensitive polymerase chain reaction (PCR)-based assay for detection of Chlamydia trachomatis in cervical specimens is described. This assay consists of (i) sample preparation which avoids the use of heat, centrifugation, or organic extractions; (ii) rapid, two-temperature PCR amplification of C. trachomatis cryptic plasmid sequences; and (iii) capture and colorimetric detection of amplified DNA in microwell plates. PCR was compared with culture by using 503 cervical specimens. After resolution of discrepant specimens with a confirmatory PCR assay directed against the chlamydial major outer membrane protein gene, PCR had a sensitivity of 97% and a specificity of 99.7% while culture had a sensitivity of 85.7% and a specificity of 100%. In a separate study, PCR was compared with a direct specimen enzyme immunoassay (Chlamydiazyme; Abbott Diagnostics) by using 375 cervical specimens. After resolution of discrepant specimens, PCR had a sensitivity and specificity of 100%, while the enzyme immunoassay had a sensitivity of 58.8% and a specificity of 100%.     

Loop-mediated isothermal amplification compared to real-time PCR and enzyme immunoassay for toxigenic Clostridium difficile detection

Clostridium difficile infection is the primary cause of health care-associated diarrhea. While most laboratories have been using rapid antigen tests for detecting C. difficile toxins, they have poor sensitivity; newer molecular methods offer rapid results with high test sensitivity and specificity. This study was designed to compare the performances of two molecular assays (Meridian illumigene and BD GeneOhm) and two antigen assays (Wampole Quik Chek Complete and TechLab Tox A/B II) to detect toxigenic C. difficile. Fecal specimens from hospitalized patients (n = 139) suspected of having C. difficile infection were tested by the four assays. Nine specimens were positive and 109 were negative by all four methods. After discrepant analysis by toxigenic culture (n = 21), the total numbers of stool specimens classified as positive and negative for toxigenic C. difficile were 21 (15%) and 118 (85%), respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were as follows: GeneOhm (95.2%, 100%, 100%, and 99.2%), illumigene (95.2%, 96.6%, 83.3%, and 99.2%), Tox A/B II (52.4%, 97.5%, 78.6%, and 92.4%), and Quik Chek Complete (47.6%, 100%, 100%, and 91.9%). The illumigene assay performed comparably to the GeneOhm assay with a slight decrease in test specificity; the sensitivities of both far exceeded those of the antigen assays. The clinical characteristics of the concordant and discrepant study patients were similar, including stool consistency and frequency. In the era of rapid molecular-based tests for toxigenic C. difficile, toxin enzyme immunoassays (EIAs) should no longer be considered the standard of care.     

Development and Validation of Digital Enzyme-Linked Immunosorbent Assays for Ultrasensitive Detection and Quantification of Clostridium difficile Toxins in Stool

The currently available diagnostics for Clostridium difficile infection (CDI) have major limitations. Despite mounting evidence that toxin detection is paramount for diagnosis, conventional toxin immunoassays are insufficiently sensitive and cytotoxicity assays too complex; assays that detect toxigenic organisms (toxigenic culture [TC] and nucleic acid amplification testing [NAAT]) are confounded by asymptomatic colonization by toxigenic C. difficile. We developed ultrasensitive digital enzyme-linked immunosorbent assays (ELISAs) for toxins A and B using single-molecule array technology and validated the assays using (i) culture filtrates from a panel of clinical C. difficile isolates and (ii) 149 adult stool specimens already tested routinely by NAAT. The digital ELISAs detected toxins A and B in stool with limits of detection of 0.45 and 1.5 pg/ml, respectively, quantified toxins across a 4-log range, and detected toxins from all clinical strains studied. Using specimens that were negative by cytotoxicity assay/TC/NAAT, clinical cutoffs were set at 29.4 pg/ml (toxin A) and 23.3 pg/ml (toxin B); the resulting clinical specificities were 96% and 98%, respectively. The toxin B digital ELISA was 100% sensitive versus cytotoxicity assay. Twenty-five percent and 22% of the samples positive by NAAT and TC, respectively, were negative by the toxin B digital ELISA, consistent with the presence of organism but minimal or no toxin. The mean toxin levels by digital ELISA were 1.5- to 1.7-fold higher in five patients with CDI-attributable severe outcomes, versus 68 patients without, but this difference was not statistically significant. Ultrasensitive digital ELISAs for the detection and quantification of toxins A and B in stool can provide a rapid and simple tool for the diagnosis of CDI with both high analytical sensitivity and high clinical specificity.     

Comparison of the VIDAS Clostridium difficile toxin A immunoassay with C. difficile culture and cytotoxin and latex tests.

The VIDAS Clostridium difficile toxin A immunoassay (CDA) is a new, automated, enzyme-linked fluorescent-antibody assay for detection of C. difficile toxin A antigen in stool specimens. Simultaneous, parallel testing was performed by using the VIDAS CDA, the Culturette brand CDT latex test for C. difficile antigens, and conventional laboratory cell culture tests for C. difficile, cytotoxicity and C. difficile culture. One hundred ninety-four consecutive fresh soft or liquid stool samples submitted for C. difficile testing between July and September 1990 were evaluated. Of the 194 samples tested, 19 (10%) were from 16 patients who met our case definition for C. difficile-associated disease. The in vitro tests were evaluated in relation to two forms of a clinical case definition. In one form, a positive culture for toxin-producing C. difficile or a positive cytotoxin result obtained directly from the stool specimen was required as laboratory evidence of C. difficile. In the other, a positive result of any of the four laboratory tests was accepted for the laboratory portion of the case definition. No significant difference between the sensitivity of the VIDAS CDA and that of the Culturette brand CDT latex test was found (48 to 58% sensitivity for the CDT latex test and 52 to 63% sensitivity for the VIDAS CDA compared with 93 to 100% sensitivity for culture and 70 to 100% sensitivity for cytotoxin testing). The performance of the VIDAS CDA, however, was hampered by a high percentage of tests (19%) which gave an uninterpretable result.     

Evaluation of a new commercialClostridium difficile toxin A enzyme immunoassay using diarrhoeal stools

A new, commercially available enzyme immunoassay for the detection of toxin A in stool specimens, the PremierClostridium difficile Toxin A test (Meridian Diagnostics), was evaluated using 228 diarrhoeal stool specimens. Using a cytotoxin assay on HeLa cells as the reference method, this new test resulted in a sensitivity of 88 % and a specificity of 95 %. Using the presence or absence of a toxigenic strain in the stools as the reference method, the sensitivity was similar to that of the cytotoxin assay (71.7 % versus 70.5 %) and the overall correlation was even better (89.4 % versus 82 %). The PremierClostridium difficile Toxin A assay is rapid and easy to perform and is an excellent alternative to the usual toxin B assay.