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

Infliximab Rescue in Acute Severe Ulcerative Colitis Complicated by Clostridium Difficile Infection: A Case Series

Relapses in inflammatory bowel disease (IBD) complicated by Clostridium difficile infection (CDI) are associated with significant morbidity and mortality. CDI can exacerbate the course of IBD and may result in prolonged hospitalizations, admissions to intensive care, surgical interventions, or even death. Early detection and aggressive treatment with systemic corticosteroids or biologics such as infliximab are often needed in severe presentations.

Five cases of relapsed ulcerative colitis complicated by fulminant CDI were retrospectively reviewed. Biological therapy with infliximab was initiated upon multidisciplinary team assessment as the cases were resistant to standard IBD therapy.

All five patients improved clinically and avoided early surgical intervention. Some required prolonged therapy with infliximab to achieve remission.

Early recognition of CDI and aggressive therapy with biologics may be required to avoid complications in the IBD patients experiencing a relapse. Infliximab therapy should be considered early on, especially where the disease is resistant to standard therapy.

A 2-step algorithm combining glutamate dehydrogenase and nucleic acid amplification tests for the detection of Clostridioides difficile in stool specimens

The optimized diagnosis algorithm of Clostridioides difficile infection (CDI) is worldwide concerns. The purpose of this study was to assess the toxigenic C. difficile test performance and propose an optimal laboratory workflow for the diagnosis of CDI in mild virulent epidemic areas. Diarrhea samples collected from patients were analyzed by glutamate dehydrogenase (GDH), toxin AB (CDAB), and nucleic acid amplification test (NAAT). We assessed the performance of GDH, the GDH-CDAB algorithm, and the GDH-NAAT algorithm using toxigenic culture (TC) as a reference method. In this study, 186 diarrhea samples were collected. The numbers of TC-positive and TC-negative samples were 39 and 147, respectively. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and kappa of the GDH assay were 100%, 80.3%, 57.4%, 100%, and 0.63; of the GDH-CDAB algorithm were 48.7%, 97.3%, 82.6%, 87.7%, and 0.54; and of the GDH-NAAT algorithm were 74.4%, 100%, 100%, 93.6%, and 0.82, respectively. The GDH-NAAT algorithm has great concordance with TC in detecting toxigenic C. difficile (kappa = 0.82), while the sensitivity of the GDH-CDAB algorithm was too low to meet the demand of CDI diagnosis clinically. GDH-NAAT algorithm is recommended for the detection of toxigenic C. difficile with high specificity, increased sensitivity, and cost-effective.

Change in the Mortality Trend of Hospitalized Patients with Clostridium difficile Infection: A Nation-wide Study

Background According to the Healthcare Cost and Utilization Project (HCUP), mortality in Clostridium difficile infection (CDI) has been rising since 2009, and an upward trend in mortality has been noted. Although there have been studies exploring the incidence of CDI and mortality in the national database, those studies were limited to one particular year. With the advent of newer modalities of diagnosis and treatment for CDI, the recent multiyear trend in disease-specific outcomes from large administrative databases is unknown. Objective To study the recent trend in nationwide hospital admissions and mortality along with hospital outcomes. Methods We queried the identified National Inpatient Sample from 2007 to 2011 to identify patients of age >18 years, with a discharge diagnosis of CDI identified by the International Classification of Diseases, 9th edition (ICD-9), clinical modification codes 008.45, respectively. Results We identified a decline in CDI mortality to 2.67% in 2011 as compared to 3.83% in 2007 (P<0.0001) with CDI as the primary discharge diagnosis and a downward trend in all-cause mortality from 9.2% in 2007 to 7.9% in 2011 (P<0.0001). We identified an upward trend in CDI-related hospital discharges from 2007 (N=325,022) to 2011 (N=333498). Hospital discharges with CDI as a primary discharge diagnosis also increased from 2007 (N=104,123) to 2011 (123,898). The mean length of stay decreased from 7.16 days in 2007 to 6.40 days in 2011 (P 0.0001). CDI was noted to be more common in the elderly (61-80), with a mean age of 68 years. Patients were of Caucasian descent (67%), female (64%), and primarily a Medicare payer (69%). Mean hospital charges increased from $31,551 to 35,654$ (P .04). Of interest, CDI was noted to be more common in large bed-sized non-teaching hospitals (57%) than large bed-sized teaching hospitals (42%). In terms of the geographical distribution of CDI, the southern states of the US had an increased incidence of CDI (36%) and the west coast (16%) had the least incidence. Conclusion  Our study shows an improved trend in-hospital mortality outcomes and a decreased length of stay likely related to the advancement in CDI treatments. Hospital charges were increased from 2007 to 2011 in spite of a decrease in hospital length of stay.

In Vitro Selection of Circular DNA Aptamers for Biosensing Applications

We report on the first effort to select DNA aptamers from a circular DNA library, which resulted in the discovery of two high-affinity circular DNA aptamers that recognize the glutamate dehydrogenase (GDH) from Clostridium difficile, an established antigen for diagnosing Clostridium difficile infection (CDI). One aptamer binds effectively in both the circular and linear forms, the other is functional only in the circular configuration. Interestingly, these two aptamers recognize different epitopes on GDH, demonstrating the advantage of selecting aptamers from circular DNA libraries. A sensitive diagnostic test was developed to take advantage of the high stability of circular DNA aptamers in biological samples and their compatibility with rolling circle amplification. This test is capable of identifying patients with active CDI using stool samples. This work represents a significant step forward towards demonstrating the practical utility of DNA aptamers in clinical diagnosis.

Enterotoxic Clostridia: Clostridioides difficile Infections

Clostridioides difficile is a Gram-positive, anaerobic, spore forming pathogen of both humans and animals and is the most common identifiable infectious agent of nosocomial antibiotic-associated diarrhea. Infection can occur following the ingestion and germination of spores, often concurrently with a disruption to the gastrointestinal microbiota, with the resulting disease presenting as a spectrum, ranging from mild and self-limiting diarrhea to severe diarrhea that may progress to life-threating syndromes that include toxic megacolon and pseudomembranous colitis. Disease is induced through the activity of the C. difficile toxins TcdA and TcdB, both of which disrupt the Rho family of GTPases in host cells, causing cell rounding and death and leading to fluid loss and diarrhea. These toxins, despite their functional and structural similarity, do not contribute to disease equally. C. difficile infection (CDI) is made more complex by a high level of strain diversity and the emergence of epidemic strains, including ribotype 027-strains which induce more severe disease in patients. With the changing epidemiology of CDI, our understanding of C. difficile disease, diagnosis, and pathogenesis continues to evolve. This article provides an overview of the current diagnostic tests available for CDI, strain typing, the major toxins C. difficile produces and their mode of action, the host immune response to each toxin and during infection, animal models of disease, and the current treatment and prevention strategies for CDI.

Clostridium difficile infection in oncology patients: epidemiology, pathophysiology, risk factors, diagnosis, and treatment

Clostridium difficile infection (CDI) is one of the most common healthcare-associated infections in the United States. Its incidence has been increasing in the recent years despite preventative measures. CDI increases annual expenses by 1.5 billion dollars. Cancer patients are at higher risk to acquire CDI, as explained by their frequent exposure to risk factors. CDI in cancer patients is associated with higher mortality rates and prolonged hospitalization. Furthermore, CDI affects the course of the disease by delaying treatments such as chemotherapy. Chemotherapeutics drugs are considered independent risk factors for CDI. This review discusses Clostridium difficile infection in cancer patients, including those who are receiving chemotherapy. Herein, we summarize recent data regarding the epidemiology, risk factors, including chemotherapy regimens, pathogenesis, diagnostic techniques and treatment options, including newer agents. Method: A literature search was performed using the PubMed and Google Scholar databases. The MeSH terms utilized in different combinations were 'clostridium difficile', 'neoplasia/cancer/oncology', 'chemotherapy', 'diagnosis', and 'treatment', in addition to looking up each treatment option individually to generate a comprehensive search. The articles were initially screened by title alone, followed by screening through abstracts. Full texts of pertinent articles (including letters to editors, case reports, case series, cohort studies, and clinical trials) were included in this review.

Evaluation of an UltraFast LabChip V280 assay for detection of toxigenic Clostridium difficile

In this study, we compared the performance of an UltraFast LabChip (UL) V280 system for Clostridium difficile detection in stool with that of Xpert C. difficile/Epi and VIDAS CDAB. Among 176 stool specimens, UL V280 detected toxigenic C. difficile in 22 (22/176, 12.5%) with a sensitivity, specificity, positive predictive value, negative predictive value (NPV) of 100.0%, 99.4%, 99.5% and 100.0%, respectively, which were higher than 95.2%, 97.4%, 83.3%, and 99.3% of Xpert C. difficile/Epi (P > 0.05). Notably, the sensitivity and NPV of ULV280 were significantly higher than those of VIDAS CDAB 52.4% (P < 0.001, odds ratio [OR] = 20.0, 95% confidence interval [CI] = 2.26-176.81) and 93.8% (P = 0.002, OR = 10.27, 95% CI = 1.30-81.17). UL V280 turnaround time (35 min) and cost (6.24 Dollars [$]) per specimen were less than those for Xpert C. difficile/Epi (47 min, 59.26 $) and VIDAS CDAB (65 min, 11.70 $). UL V280 possessed an analytical sensitivity limit of 2500 CFU/ml, 95% [CI] = (Ct: 30.76-34.90), and no cross-reactions with other pathogens were found. The study demonstrates that UL V280 based on a microfluidic chip is a rapid, accurate, easy, and cost-effective diagnostic test for toxigenic C. difficile in stool.

Molecular Microbiology

Background

Nucleic acid (NA) amplification techniques are now commonly used to diagnose and manage patients with infectious diseases. The growth in the number of Food and Drug Administration–approved test kits and analyte-specific reagents has facilitated the use of this technology in clinical laboratories. Technological advances in NA amplification techniques, automation, NA sequencing, and multiplex analysis have reinvigorated the field and created new opportunities for growth. Simple, sample-in, answer-out molecular test systems are now widely available that can be deployed in a variety of laboratory and clinical settings. Molecular microbiology remains the leading area in molecular pathology in terms of both the numbers of tests performed and clinical relevance. NA-based tests have reduced the dependency of the clinical microbiology laboratory on more traditional antigen detection and culture methods and created new opportunities for the laboratory to impact patient care.

Content

This chapter reviews NA testing as it applies to specific pathogens or infectious disease syndromes, with a focus on those diseases for which NA testing is now considered the standard of care and highlights the unique challenges and opportunities that these tests present for clinical laboratories.

Can a toxin gene NAAT be used to predict toxin EIA and the severity of Clostridium difficile infection?

Background

Diagnosis of C. difficile infection (CDI) is controversial because of the many laboratory methods available and their lack of ability to distinguish between carriage, mild or severe disease. Here we describe whether a low C. difficile toxin B nucleic acid amplification test (NAAT) cycle threshold (CT) can predict toxin EIA, CDI severity and mortality.

Methods

A three-stage algorithm was employed for CDI testing, comprising a screening test for glutamate dehydrogenase (GDH), followed by a NAAT, then a toxin enzyme immunoassay (EIA). All diarrhoeal samples positive for GDH and NAAT between 2012 and 2016 were analysed. The performance of the NAAT CT value as a classifier of toxin EIA outcome was analysed using a ROC curve; patient mortality was compared to CTs and toxin EIA via linear regression models.

Results

A CT value ≤26 was associated with ≥72% toxin EIA positivity; applying a logistic regression model we demonstrated an association between low CT values and toxin EIA positivity. A CT value of ≤26 was significantly associated (p = 0.0262) with increased one month mortality, severe cases of CDI or failure of first line treatment. The ROC curve probabilities demonstrated a CT cut off value of 26.6.

Discussions

Here we demonstrate that a CT ≤26 indicates more severe CDI and is associated with higher mortality. Samples with a low CT value are often toxin EIA positive, questioning the need for this additional EIA test.

Conclusions

A CT ≤26 could be used to assess the potential for severity of CDI and guide patient treatment.

Detection of toxigenic Clostridioides [Clostridium] difficile: Usefulness of two commercially available enzyme immunoassays and a PCR assay on stool samples and stool isolates

The best laboratory diagnostic approach to detect Clostridioides [Clostridium] difficile infection (CDI) is a subject of ongoing debate. With the aim of evaluating four laboratory diagnostic methods, 250 unformed stools from patients with suspected CDI submitted to nine medical center laboratories from November 2010 to December 2011, were studied using: (1) an immunochromatographic rapid assay test that combines the qualitative determination of glutamate dehydrogenase (GDH) plus toxins A and B (QAB), the CDIFF QUIK CHEK COMPLETE assay; (2) an enzyme immunoassay for qualitative determination of toxins A and B, the RIDASCREEN™ C. difficile Toxin A/B assay (RAB); (3) a PCR for the toxin B gene assay (PCR); and (4) the toxigenic culture (TC). C. difficile isolates from direct toxin negative stools by QAB, RAB and PCR were evaluated for toxigenicity by the same direct tests, in order to assess the contribution of the TC (QAB-TC, RAB-TC, PCR-TC). A combination of the cell culture cytotoxicity neutralization assay (CCCNA) in stools, and the same assay on isolates from direct negative samples (CCCNA-TC) was considered the reference method (CCCNA/CCCNA-TC). Of the 250 stools tested, 107 (42.8%) were positive by CCCNA/CCCNA-TC. The GDH and PCR/PCR-TC assays were the most sensitive, 91.59% and 87.62%, respectively. The QAB, RAB, QAB/QAB-TC and RAB/RAB-TC had the highest specificities, ca. 95%. A negative GDH result would rule out CDI, however, its low positive likelihood ratio (PLR) of 3.97 indicates that a positive result should always be complemented with the detection of toxins. If the RAB, QAB, and PCR assays do not detect toxins from direct feces, the toxigenic culture should be performed. In view of our results, the most accurate and reliable methods to be applied in a clinical microbiology laboratory were the QAB/QAB-TC, and RAB/RAB-TC, with PLRs >10 and negative likelihood ratios <0.30.

Rapid detection of Clostridium difficile toxins and laboratory diagnosis of Clostridium difficile infections

BACKGROUND

Clostridium difficile is an anaerobic, spore-forming and Gram-positive bacillus. It is the major cause of antibiotic-associated diarrhea prevailing in hospital settings. The morbidity and mortality of C. difficile infection (CDI) has increased significantly due to the emergence of hypervirulent strains. Because of the poor clinical different between CDI and other causes of hospital-acquired diarrhea, laboratory test for C. difficile is an important intervention for diagnosis of CDI.

OBJECTIVE

Laboratory tests for CDI can broadly detect either the organisms or its toxins. Currently, several laboratory tests are used for diagnosis of CDI, including toxigenic culture, glutamate dehydrogenase detection, nucleic acid amplification testing, cell cytotoxicity assay, and enzyme immunoassay towards toxin A and/or B. This review focuses on the rapid testing of C. difficile toxins and currently available methods for diagnosis of CDI, giving an overview of the role that the toxins rapid detecting plays in clinical diagnosis of CDI.

Selected Topics in Anaerobic Bacteriology

Alteration in the host microbiome at skin and mucosal surfaces plays a role in the function of the immune system, and may predispose immunocompromised patients to infection. Because obligate anaerobes are the predominant type of bacteria present in humans at skin and mucosal surfaces, immunocompromised patients are at increased risk for serious invasive infection due to anaerobes. Laboratory approaches to the diagnosis of anaerobe infections that occur due to pyogenic, polymicrobial, or toxin-producing organisms are described. The clinical interpretation and limitations of anaerobe recovery from specimens, anaerobe-identification procedures, and antibiotic-susceptibility testing are outlined. Bacteriotherapy following analysis of disruption of the host microbiome has been effective for treatment of refractory or recurrent Clostridium difficile infection, and may become feasible for other conditions in the future.

European Society of Clinical Microbiology and Infectious Diseases: update of the diagnostic guidance document for Clostridium difficile infection

In 2009 the first European Society of Clinical Microbiology and Infectious Diseases (ESCMID) guideline for diagnosing Clostridium difficile infection (CDI) was launched. Since then newer tests for diagnosing CDI have become available, especially nucleic acid amplification tests. The main objectives of this update of the guidance document are to summarize the currently available evidence concerning laboratory diagnosis of CDI and to formulate and revise recommendations to optimize CDI testing. This update is essential to improve the diagnosis of CDI and to improve uniformity in CDI diagnosis for surveillance purposes among Europe. An electronic search for literature concerning the laboratory diagnosis of CDI was performed. Studies evaluating a commercial laboratory test compared to a reference test were also included in a meta-analysis. The commercial tests that were evaluated included enzyme immunoassays (EIAs) detecting glutamate dehydrogenase, EIAs detecting toxins A and B and nucleic acid amplification tests. Recommendations were formulated by an executive committee, and the strength of recommendations and quality of evidence were graded using the Grades of Recommendation Assessment, Development and Evaluation (GRADE) system. No single commercial test can be used as a stand-alone test for diagnosing CDI as a result of inadequate positive predictive values at low CDI prevalence. Therefore, the use of a two-step algorithm is recommended. Samples without free toxin detected by toxins A and B EIA but with positive glutamate dehydrogenase EIA, nucleic acid amplification test or toxigenic culture results need clinical evaluation to discern CDI from asymptomatic carriage.

Recent Advances in the Diagnosis and Treatment of Clostridium Difficile Infection

Clostridium difficile infection (CDI) has become the most frequently reported health care-associated infection in the United States [1]. As the incidence of CDI rises, so too does the burden it produces on health care and society. In an attempt to decrease the burden of CDI and provide the best outcomes for patients affected by CDI, there have been many recent advancements in the understanding, diagnosis, and management of CDI. In this article, we review the current recommendations regarding CDI testing and treatment strategies.

The Role of Glutamate Dehydrogenase (GDH) Testing Assay in the Diagnosis of Clostridium difficile Infections: A High Sensitive Screening Test and an Essential Step in the Proposed Laboratory Diagnosis Workflow for Developing Countries like China

The incidence and severity of Clostridium difficile infection (CDI) in North America and Europe has increased significantly since the 2000s. However, CDI is not widely recognized in China and other developing countries due to limited laboratory diagnostic capacity and low awareness. Most published studies on laboratory workflows for CDI diagnosis are from developed countries, and thus may not be suitable for most developing countries. Therefore, an alternative strategy for developing countries is needed. In this study, we evaluated the performance of the Glutamate Dehydrogenase (GDH) test and its associated workflow on 416 fecal specimens from suspected CDI cases. The assay exhibited excellent sensitivity (100.0%) and specificity (92.8%), compared to culture based method, and thus could be a good screening marker for C. difficile but not for indication of toxin production. The VIDAS CDAB assay, which can detect toxin A/B directly from fecal specimens, showed good specificity (99.7%) and positive predictive value (97.2%), but low sensitivity (45.0%) and negative predictive value (88.3%), compared with PCR-based toxin gene detection. Therefore, we propose a practical and efficient GDH test based workflow strategy for the laboratory diagnosis of CDI in developing countries like China. By applying this new workflow, the CDI laboratory diagnosis rate was notably improved in our center, yet the increasing cost was kept at a minimum level. Furthermore, to gain some insights into the genetic population structure of C. difficile isolates from our hospital, we performed MLST and PCR toxin gene typing.

Pitfalls in Diagnosis of Pediatric Clostridium difficile Infection

The incidence of Clostridium difficile infection (CDI) has risen among children and C difficile is increasingly recognized as an important cause of healthcare-associated diarrhea among pediatric patients. Still, increased identification of CDI in healthy children in the community and increased testing among infants requires cautious interpretation, given the high prevalence of asymptomatic colonization in young infants and frequent detection of viruses and other co-pathogens in stool specimens in these age groups. The significance of CDI among infants and the implications of positive C difficile testing among healthy children in the community are areas in need of further study.

Clostridium Difficile Colitis in Trauma Patients - a Global Step by Step Review

Clostridium difficile associated disease is a well recognized nosocomial infection evolving as a severediarrheal illness, associated with significantly higher rates of morbidity and mortality in critically ill patients. The incidence of Clostridium difficile infection is higher and its impact is more severe in trauma patients when compared with general inpatient population. There are several potential diagnosis tools for Clostridium difficile colitis, however choosing the right diagnostic approach is a difficult task, especially in trauma patients in whom a rapid and certain diagnosis is of paramount importance. Moreover, managing these patients may prove to be a very challenging task, considering the emergence of novel aggressive Clostridium difficile strains resulting in increased disease severity.

Optimizing the Laboratory Diagnosis of Clostridium difficile Infection

The best laboratory diagnostic approach to detect Clostridium difficile infection (CDI) is the subject of ongoing debate. In the United States, nucleic acid amplification tests (NAAT) have become the most widely used tests for making this diagnosis. Detection of toxin in stool may be a better predictor of CDI disease and severity. Laboratories that have switched from toxin-based to NAAT-based methods have significantly higher CDI detection rates. The important issue is whether all NAAT-positive patients have CDI or at least some of those patients are excretors of the organism and do not have clinical disease.

In Vitro Selection of a Single-Stranded DNA Molecular Recognition Element against Clostridium difficile Toxin B and Sensitive Detection in Human Fecal Matter

Toxin B is one of the major virulence factors of Clostridium difficile, a bacterium that is responsible for a significant number of diarrhea cases in acute care settings. Due to the prevalence of C. difficile induced diarrhea, rapid and correct diagnosis is crucial in the disease management. In this study, we have employed a stringent in vitro selection method to identify single-stranded DNA molecular recognition elements (MRE) specific for toxin B. At the end of the 12-round selection, one MRE with high affinity (K d = 47.3 nM) for toxin B was identified. The selected MRE demonstrated low cross binding activities on negative targets: bovine serum albumin, Staphylococcus aureus alpha toxin, Pseudomonas aeruginosa exotoxin A, and cholera toxin of Vibrio cholera. A modified sandwich ELISA assay was developed utilizing the selected ssDNA MRE as the antigen capturing element and achieved a sensitive detection of 50 nM of toxin B in human fecal preparations.

Clinical Practice Guidelines for Clostridium difficile Infection in Adults: 2010 Update by the Society for Healthcare Epidemiology of America (SHEA) and the Infectious Diseases Society of America (IDSA)

Since publication of the Society for Healthcare Epidemiology of America position paper onClostridium difficileinfection in 1995, significant changes have occurred in the epidemiology and treatment of this infection.C. difficileremains the most important cause of healthcare-associated diarrhea and is increasingly important as a community pathogen. A more virulent strain ofC. difficilehas been identified and has been responsible for more-severe cases of disease worldwide. Data reporting the decreased effectiveness of metronidazole in the treatment of severe disease have been published. Despite the increasing quantity of data available, areas of controversy still exist. This guideline updates recommendations regarding epidemiology, diagnosis, treatment, and infection control and environmental management.

High Proportion of False-Positive Clostridium difficile Enzyme Immunoassays for Toxin A and B in Pediatric Patients

Objectives.

To determine the frequency of false-positive Clostridium difficile toxin enzyme immunoassay (EIA) results in hospitalized children and to examine potential reasons for this false positivity.

Design.

Nested case-control.

Setting.

Two tertiary care pediatric hospitals.

Methods.

As part of a natural history study, prospectively collected EIA-positive stools were cultured for toxigenic C. difficile, and characteristics of children with false-positive and true-positive EIA results were compared. EIA-positive/culture-negative samples were recultured after dilution and enrichment steps, were evaluated for presence of the tcdB gene by polymerase chain reaction (PCR), and were further cultured for Clostridium sordellii, a cause of false-positive EIA toxin assays.

Results.

Of 112 EIA-positive stools cultured, 72 grew toxigenic C. difficile and 40 did not, indicating a positive predictive value of 64% in this population. The estimated prevalence of C. difficile infection (CDI) in the study sites among children tested for this pathogen was 5%–7%. Children with false-positive EIA results were significantly younger than those with true-positive tests but did not differ in other characteristics. No false-positive specimens yielded C. difficile when cultured after enrichment or serial dilution, 1 specimen was positive for tcdB by PCR, and none grew C. sordellii.

Conclusions.

Approximately one-third of EIA tests used to evaluate pediatric inpatients for CDI were falsely positive. This finding was likely due to the low prevalence of CDI in pediatric hospitals, which diminishes the test's positive predictive value. These data raise concerns about the use of EIA assays to diagnosis CDI in children.

Infect Control Hosp Epidemiol 2012;33(2):175-179

Clostridium difficile Infection Is More Severe When Toxin Is Detected in the Stool than When Detected Only by a Toxigenic Culture

OBJECTIVE

Clostridium difficile infection (CDI) is the major cause of antibiotic-associated diarrhea in hospital inpatients. Rapid testing for the toxins in stool specimens is inconclusive due to its low sensitivity. Therefore, a two-step method is recommended as the most appropriate approach. The purpose of the present study was to evaluate the differences in the disease severity score between the patients who were glutamate dehydrogenase (GDH)-positive/enzyme immunoassays (EIA) toxin-positive (group A) and those who were GDH-positive/EIA toxin-negative, but who were nonetheless finally confirmed to be toxin-positive by toxigenic culture testing (group B).

METHODS

A rapid detection EIA for GDH and toxin A/B were simultaneously performed for initial screening. Subsequently, the toxin production by bacterial colonies in culture was retested with the same rapid test kit when necessitated by an equivocal result of the initial screening.

RESULTS

A total of 334 fecal specimens were evaluated. Group A consisted of 25 specimens (from 16 patients) and group B consisted of 27 specimens (from 12 patients). The severity score (based on a number of factors, including age, body temperature, serum albumin level and white cell count) of group A and B was 2.2±0.7 and 1.4±0.5, respectively (p=0.002).

CONCLUSION

The cases of CDI in which the toxins were detected by the initial screening test were more severe than those where the toxins were not detected at the initial screening but were identified by the toxigenic culture. In addition, the most significant factors affecting the severity score were an older age and a lower serum albumin level.

Real-time cellular analysis for quantitative detection of functional Clostridium difficile toxin in stool

Rapid and accurate diagnosis and monitoring of Clostridium difficile infection (CDI) is critical for patient care and infection control. We will briefly review current laboratory techniques for the diagnosis of CDI and identify aspects needing improvement. We will also introduce a real-time cellular analysis (RTCA) assay developed for the diagnosis and monitoring of CDI using electronic impedance to assess the cell status. The RTCA assay uses impedance measurement to detect minute physiological changes in cells cultured on gold microelectrodes embedded in glass substrates in the bottom of microtiter wells. This assay has been adapted for quantitative detection of C. difficile functional toxin directly from stool specimens. Compared to conventional techniques and molecular assays, the RTCA assay provides a valuable tool for the diagnosis of CDI as well as for the assessment of clinical severity and for monitoring therapeutic efficacies.

Evaluation of a rapid membrane enzyme immunoassay for the simultaneous detection of glutamate dehydrogenase and toxin for the diagnosis of Clostridium difficile infection

We evaluated the new C. DIFF QUIK CHEK COMPLETE (CD COMPLETE; TechLab, USA), which is a rapid membrane enzyme immunoassay that uses a combination of glutamate dehydrogenase (GDH) antigen and toxin A and B detection. A total of 608 consecutive loose stool specimens collected from the patients with suspected Clostridium difficile infection (CDI) from August to December 2012 were subjected to the CD COMPLETE and VIDAS Clostridium difficile A & B (VIDAS CDAB; bioMérieux, France). Their performances were compared with a toxigenic culture as a reference. Stool specimens that were culture-negative and CD COMPLETE- or VIDAS CDAB-positive were analyzed by using an enrichment procedure. In comparison to the toxigenic cultures, sensitivity, specificity, positive predictive values (PPV), and negative predictive values (NPV) were 63.6%, 98.0%, 76.1%, and 96.4%, respectively, for the CD COMPLETE-toxin and 75.5%, 97.4%, 72.5%, and 97.8%, respectively, for the VIDAS CDAB. In comparison to the enriched C. difficile cultures, the sensitivity, specificity, PPV, and NPV for the CD COMPLETE-GDH were 91.0%, 92.4%, 70.5%, and 98.1%, respectively. The CD COMPLETE is a reliable method for the diagnosis of CDI and provides greater sensitivity than toxin enzyme immunoassay alone. Furthermore, the CD COMPLETE-GDH has advantages over direct culture in detecting C. difficile.

Clinical update for the diagnosis and treatment of Clostridium difficile infection

Clostridium difficile infection (CDI) presents a rapidly evolving challenge in the battle against hospital-acquired infections. Recent advances in CDI diagnosis and management include rapid changes in diagnostic approach with the introduction of newer tests, such as detection of glutamate dehydrogenase in stool and polymerase chain reaction to detect the gene for toxin production, which will soon revolutionize the diagnostic approach to CDI. New medications and multiple medical society guidelines have introduced changing concepts in the definitions of severity of CDI and the choice of therapeutic agents, while rapid expansion of data on the efficacy of fecal microbiota transplantation heralds a revolutionary change in the management of patients suffering multiple relapses of CDI. Through a comprehensive review of current medical literature, this article aims to offer an intensive review of the current state of CDI diagnosis, discuss the strengths and limitations of available laboratory tests, compare both current and future treatments options and offer recommendations for best practice strategies.

Combination of culture, antigen and toxin detection, and cytotoxin neutralization assay for optimal Clostridium difficile diagnostic testing

BACKGROUND

There has been a growing interest in developing an appropriate laboratory diagnostic algorithm for Clostridium difficile, mainly as a result of increases in both the number and severity of cases of C difficile infection in the past decade. A C difficile diagnostic algorithm is necessary because diagnostic kits, mostly for the detection of toxins A and B or glutamate dehydrogenase (GDH) antigen, are not sufficient as stand-alone assays for optimal diagnosis of C difficile infection. In addition, conventional reference methods for C difficile detection (eg, toxigenic culture and cytotoxin neutralization [CTN] assays) are not routinely practiced in diagnostic laboratory settings.

OBJECTIVE

To review the four-step algorithm used at Diagnostic Services of Manitoba sites for the laboratory diagnosis of toxigenic C difficile.

RESULT

One year of retrospective C difficile data using the proposed algorithm was reported. Of 5695 stool samples tested, 9.1% (n=517) had toxigenic C difficile. Sixty per cent (310 of 517) of toxigenic C difficile stools were detected following the first two steps of the algorithm. CTN confirmation of GDH-positive, toxin A- and B-negative assays resulted in detection of an additional 37.7% (198 of 517) of toxigenic C difficile. Culture of the third specimen, from patients who had two previous negative specimens, detected an additional 2.32% (12 of 517) of toxigenic C difficile samples.

DISCUSSION

Using GDH antigen as the screening and toxin A and B as confirmatory test for C difficile, 85% of specimens were reported negative or positive within 4 h. Without CTN confirmation for GDH antigen and toxin A and B discordant results, 37% (195 of 517) of toxigenic C difficile stools would have been missed. Following the algorithm, culture was needed for only 2.72% of all specimens submitted for C difficile testing.

CONCLUSION

The overview of the data illustrated the significance of each stage of this four-step C difficile algorithm and emphasized the value of using CTN assay and culture as parts of an algorithm that ensures accurate diagnosis of toxigenic C difficile.

Diagnosis of Clostridium difficile infection: an ongoing conundrum for clinicians and for clinical laboratories

Clostridium difficile is a formidable nosocomial and community-acquired pathogen, causing clinical presentations ranging from asymptomatic colonization to self-limiting diarrhea to toxic megacolon and fulminant colitis. Since the early 2000s, the incidence of C. difficile disease has increased dramatically, and this is thought to be due to the emergence of new strain types. For many years, the mainstay of C. difficile disease diagnosis was enzyme immunoassays for detection of the C. difficile toxin(s), although it is now generally accepted that these assays lack sensitivity. A number of molecular assays are commercially available for the detection of C. difficile. This review covers the history and biology of C. difficile and provides an in-depth discussion of the laboratory methods used for the diagnosis of C. difficile infection (CDI). In addition, strain typing methods for C. difficile and the evolving epidemiology of colonization and infection with this organism are discussed. Finally, considerations for diagnosing C. difficile disease in special patient populations, such as children, oncology patients, transplant patients, and patients with inflammatory bowel disease, are described. As detection of C. difficile in clinical specimens does not always equate with disease, the diagnosis of C. difficile infection continues to be a challenge for both laboratories and clinicians.

Enteric infections

Cancer patients, particularly those with neutropenia, are at risk for enteric and intra-abdominal infections. Specific infections and infectious syndromes in this setting include neutropenic enterocolitis, bacterial infections such as Clostridium difficile infection (CDI), viral infections such as CMV colitis, and parasitic infections such as strongyloidiasis. Diagnosing and gauging the severity of CDI presents challenges, as chemotherapy may produce symptoms that mimic CDI and laboratory findings such as leukocytosis are not reliable in this population. Treatment for enteric infections should be pathogen specific, although broad-spectrum antibiotics are often required as initial empiric therapy in patients with neutropenia.

Clostridium difficile Infection: Epidemiology, Pathogenesis, Risk Factors, and Therapeutic Options

The incidence and mortality rate of Clostridium difficile infection have increased remarkably in both hospital and community settings during the last two decades. The growth of infection may be caused by multiple factors including inappropriate antibiotic usage, poor standards of environmental cleanliness, changes in infection control practices, large outbreaks of C. difficile infection in hospitals, alteration of circulating strains of C. difficile, and spread of hypervirulent strains. Detection of high-risk populations could be helpful for prompt diagnosis and consequent treatment of patients suffering from C. difficile infection. Metronidazole and oral vancomycin are recommended antibiotics for the treatment of initial infection. Current treatments for C. difficile infection consist of supportive care, discontinuing the unnecessary antibiotic, and specific antimicrobial therapy. Moreover, novel approaches include fidaxomicin therapy, monoclonal antibodies, and fecal microbiota transplantation mediated therapy. Fecal microbiota transplantation has shown relevant efficacy to overcome C. difficile infection and reduce its recurrence.

Portrait Toxigenic Clostridium difficile assay, an isothermal amplification assay detects toxigenic C. difficile in clinical stool specimens

The Portrait Toxigenic Clostridium difficile assay is a rapid, qualitative assay for the detection of the tcdB gene of C. difficile in stool specimens from patients suspected of C. difficile infections, and received 510(k) clearance by the US FDA in March 2012. The Portrait Toxigenic C. difficile assay combines novel blocked-primer-mediated helicase-dependent multiplex amplification (bpHDA) technology and chip-based detection in an automated sample-to-result format. The assay requires minimal sample preparation and results are available within 90 min. In a multicenter evaluation, the Portrait Toxigenic C. difficile assay had a sensitivity of 98.2% and specificity of 92.8% compared with toxigenic culture. A comparative study between the Portrait Toxigenic C. difficile assay and three FDA-cleared molecular assays for the detection of toxigenic C. difficile exhibited a high degree of agreement (93.8-97.5%). The Portrait Toxigenic C. difficile assay provides a simple, cost-effective method with broad applicability to panel-based approaches, potentially simplifying workflow.

Differences in outcome according to Clostridium difficile testing method: a prospective multicentre diagnostic validation study of C difficile infection

Background

Diagnosis of Clostridium difficile infection is controversial because of many laboratory methods, compounded by two reference methods. Cytotoxigenic culture detects toxigenic C difficile and gives a positive result more frequently (eg, because of colonisation, which means that individuals can have the bacterium but no free toxin) than does the cytotoxin assay, which detects preformed toxin in faeces. We aimed to validate the reference methods according to clinical outcomes and to derive an optimum laboratory diagnostic algorithm for C difficile infection.

Methods

In this prospective, multicentre study, we did cytotoxigenic culture and cytotoxin assays on 12 420 faecal samples in four UK laboratories. We also performed tests that represent the three main targets for C difficile detection: bacterium (glutamate dehydrogenase), toxins, or toxin genes. We used routine blood test results, length of hospital stay, and 30-day mortality to clinically validate the reference methods. Data were categorised by reference method result: group 1, cytotoxin assay positive; group 2, cytotoxigenic culture positive and cytotoxin assay negative; and group 3, both reference methods negative.

Findings

Clinical and reference assay data were available for 6522 inpatient episodes. On univariate analysis, mortality was significantly higher in group 1 than in group 2 (72/435 [16·6%] vs 20/207 [9·7%], p=0·044) and in group 3 (503/5880 [8·6%], p<0·001), but not in group 2 compared with group 3 (p=0·4). A multivariate analysis accounting for potential confounders confirmed the mortality differences between groups 1 and 3 (OR 1·61, 95% CI 1·12–2·31). Multistage algorithms performed better than did standalone assays.

Interpretation

We noted no increase in mortality when toxigenic C difficile alone was present. Toxin (cytotoxin assay) positivity correlated with clinical outcome, and so this reference method best defines true cases of C difficile infection. A new diagnostic category of potential C difficile excretor (cytotoxigenic culture positive but cytotoxin assay negative) could be used to characterise patients with diarrhoea that is probably not due to C difficile infection, but who can cause cross-infection.

Funding

Department of Health and Health Protection Agency, UK.

Overview of severe Clostridium difficile infection

Clostridium difficile is an anaerobic, spore-forming, gram-positive bacillus that can produce severe colitis resulting in death. There has been an overall increase in the incidence of Clostridium difficile-associated disease and, particularly, an increase in the more virulent forms of the disease. Treatment of severe C difficile infection includes management of severe sepsis and shock, pathogen-directed antibiotic therapy, and, in selected cases, surgical intervention. Ultimately, prevention is the key to limiting the devastating effects of this microorganism.

Laboratory diagnosis of Clostridium difficile infections: there is light at the end of the colon

Single molecular or multistep assays (glutamate dehydrogenase, toxin A/B, ± molecular) are recommended for the diagnosis of CDI in patients with clinically significant diarrhea. Rapid and accurate tests can improve resource allocations and improve patient care. Enzyme immunoassay (EIA) for toxins A/B is too insensitive for use as a stand-alone assay. This guideline will examine the use of molecular tests and multitest algorithms for the diagnosis of Clostridium difficile infection (CDI). These new tests, alone or in a multistep algorithm consisting of >1 assay, are more expensive than the older EIA assays; however, rapid and accurate testing can save money overall by initiating appropriate treatment and infection control protocols sooner and by possibly reducing length of hospital stay. We recommend testing only unformed stool in patients with clinically significant diarrhea by a molecular method or by a 2- to 3-step algorithm.

Detection of Clostridium difficile toxins A, B and binary toxin with slow off-rate modified aptamers

Rapid and accurate diagnostic tests for Clostridium difficile infections (CDI) are crucial for management of patients with suspected CDI and for infection control. Enzyme immunoassays for detection of the toxins are routinely used but lack adequate sensitivity. We generated slow off-rate modified aptamers (SOMAmer™ reagents) via in vitro selection (SELEX) that bind toxins A, B and binary toxin with high affinity and specificity. Using SOMAmers alone or in conjunction with antibodies, we have developed toxin assays with a 1 pmol/L (300 pg/mL) limit of detection and a 3 log dynamic range. SOMAmers proved useful as capture or detection agents in equilibrium solution binding radioassays, pull-down capture assays, dot blots, and plate- or membrane-based sandwich assays, thus represent a promising alternative to antibodies in diagnostic applications. SOMAmers detected toxins A, B and binary toxin in culture supernatants from toxigenic C. difficile, including a BI/NAP1 strain and historic strains.

Clinical impact of switching conventional enzyme immunoassay with nucleic acid amplification test for suspected Clostridium difficile-associated diarrhea

The impact of a new Clostridium difficile nucleic acid amplification test (NAAT) on antibiotic utilization in patients with suspected C difficile infection was assessed. This single-center, cross-sectional study of 270 patients demonstrated that the use of NAAT decreased antibiotic expenditure by reducing prolonged empiric days of therapy in these patients.

Diagnosis and management of gastrointestinal complications in adult cancer patients: evidence-based guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO)

BACKGROUND

Cancer patients frequently suffer from gastrointestinal complications. However, a comprehensive, practical and evidence-based guideline on this issue is not yet available.

PATIENTS AND METHODS

An expert group was put together by the Infectious Diseases Working Party (AGIHO) of the German Society of Hematology and Oncology (DGHO) to develop a guideline on gastrointestinal complications in cancer patients. For each subtopic, a literature search was carried out in PubMed, Medline and Cochrane databases and the strength of recommendation and the quality of the published evidence for major therapeutic strategies were categorized using a modification of the 'Infectious Diseases Society of America' criteria. Consensus discussions were held on each of the topics.

RESULTS

Recommendations were made with respect to non-infectious and infectious gastrointestinal complications. For all recommendations, the strength of the recommendation and the level of evidence are presented.

CONCLUSION

This guideline is an evidence-based approach to the diagnosis and management of gastrointestinal complications in cancer patients.

Comparison of analytical and clinical performance of three methods for detection of Clostridium difficile

CONTEXT

Diagnostic laboratory testing for Clostridium difficile infection has undergone considerable and rapid evolution during the last decade. The ideal detection method(s), which should exhibit high analytical and clinical sensitivity and specificity, remains undefined.

OBJECTIVE

We sought to evaluate the analytical and clinical performance characteristics of three methods for the laboratory detection of C difficile.

DESIGN

This study used 114 consecutive stool samples to compare three methods of C difficile detection: an enzyme immunoassay (EIA) for toxins A/B, a lateral flow membrane immunoassay for glutamate dehydrogenase (GDH), and a qualitative real-time polymerase chain reaction (PCR) assay. Medical records of all patients having ≥1 positive test result were reviewed to estimate the clinical likelihood of C difficile infection.

RESULTS

Based upon laboratory result consensus values, analytical sensitivity was significantly higher for GDH (94%) and PCR (94%) assays than for toxin EIA (25%). Analytical specificity was significantly higher for PCR (100%) and EIA (100%) than for GDH assay (93%). In contrast, assay performance based upon clinical probability of C difficile infection suggested lower discriminatory power (ie, clinical specificity) of the more analytically sensitive methods.

CONCLUSIONS

Higher rates of C difficile detection will be realized upon implementation of GDH assay and/or real-time PCR-based testing algorithms than by testing with EIA alone. Further study is required to elucidate potential downstream costs for higher detection rates.

Multicenter clinical evaluation of the portrait toxigenic C. difficile assay for detection of toxigenic Clostridium difficile strains in clinical stool specimens

We compared the Portrait Toxigenic C. difficile Assay, a new semiautomated sample-to-result molecular test, to a toxigenic bacterial culture/cell cytotoxin neutralization assay (TBC/CCNA) for the detection of toxigenic Clostridium difficile in 549 stool specimens. Stool specimens were also tested by one of three alternative FDA-cleared molecular tests for toxigenic C. difficile (Xpert C. difficile, Illumigene C. difficile, or GeneOhm Cdiff). The sensitivities and specificities of the molecular tests compared to TBC/CCNA were as follows: 98.2% and 92.8% for the Portrait assay, 100% and 91.7% for the Xpert assay, 93.3% and 95.1% for the Illumigene assay, and 97.4% and 98.5% for the GeneOhm assay, respectively. The majority of Portrait false-positive results (20/31; 64.5%) were also positive for C. difficile by an alternative molecular test, suggesting an increased sensitivity compared to the culture-based "gold standard" method. The Portrait test detected an assay input of 30 CFU in 100% of spiked samples and detected an input of 10 CFU in 96.7% of samples tested.

The value of repeat Clostridium difficile toxin testing during and after an outbreak of C difficile-associated diarrhea

BACKGROUND

The recent increase in Clostridium difficile-associated diarrhea (CDAD) has led to questions about the reproducibility and sensitivity of C difficile toxin testing (CDTT). While there have been recommendations to repeat CDTT following a negative result, previous studies have failed to show a benefit. However, no studies were performed during an outbreak of CDAD. The value of repeat CDTT after an initial negative result in patients tested during and after an outbreak of CDAD is reported in the present study, as well as the reproducibility of CDTT when multiple samples are received and tested on the same day.

METHODS

The results of CDTT, performed using a cell cytotoxicity assay between April 1, 2001, and March 31, 2008, were retrieved and searched for patients who had repeat samples tested after an initial negative result. The result and the number of days after a negative result were determined using the date of the most recent negative test. The cumulative positivity rate was calculated by adding all of the repeat positive test results for the days in question and dividing by the total number of tests performed during that time.

RESULTS

A total of 8661 patients submitted 14,991 stool specimens for CDTT during the study period. There were 3095 samples that tested positive (20.6%) for the toxin. The results were divided into two time periods to reflect the CDAD outbreak, which began in April 2002: period 1 (outbreak) was from April 1, 2002, to March 31, 2006, and period 2 was from April 1, 2006, to March 31, 2008. The rate of positivity was 24.2% during period 1, and 11.6% during period 2 (P<0.001). Repeat CDTT was performed 619 times on samples received on the same day as the initial specimen, and only three (0.5%) were discordant. A total of 1630 samples were retested within one to seven days of a negative result, and 103 (6.3%) tested positive (7.8% period 1 and 2.9% period 2; P=0.002). The likelihood of a positive result on repeat testing in the first three days after a negative result was low (0.9%, 7% and 4%, respectively). The cumulative positivity for repeat testing performed in the first three days was 0.9%, 3.3% and 3.5%, respectively, and did not differ significantly at day 3 during the period of high CDTT positivity (P=0.110).

CONCLUSIONS

The value of repeat CDTT, performed using a cell cytotoxicity assay, was low in the first three days after an initial negative result and was unchanged during a CDAD outbreak.

Evolution of testing algorithms at a university hospital for detection of Clostridium difficile infections

We present the evolution of testing algorithms at our institution in which the C. Diff Quik Chek Complete immunochromatographic cartridge assay determines the presence of both glutamate dehydrogenase and Clostridium difficile toxins A and B as a primary screen for C. difficile infection and indeterminate results (glutamate dehydrogenase positive, toxin A and B negative) are confirmed by the GeneXpert C. difficile PCR assay. This two-step algorithm is a cost-effective method for highly sensitive detection of toxigenic C. difficile.

Evaluation of three enzyme immunoassays and a loop-mediated isothermal amplification test for the laboratory diagnosis of Clostridium difficile infection

The laboratory diagnosis of Clostridium difficile infection (CDI) consists of the detection of toxigenic Clostridium difficile, and/or its toxins A or B in stool preferably in a two-step algorithm. In a prospective study, we compared the performance of three toxin enzyme immunoassays (EIAs)-ImmunoCard Toxins A & B, Premier Toxins A & B and C. diff Quik Chek Complete, which combines a toxins test and a glutamate dehydrogenase (GDH) antigen EIA in one device -and the loop-mediated isothermal amplification assay Illumigene C. difficile. In total 986 stool samples were analyzed. Compared with toxigenic culture as the gold standard, sensitivities, specificities, PPV and NPV values of the toxin EIAs were 41.1-54.8 %, 98.9-100 %, 75.0-100 % and 95.5-96.5 % respectively, of the Illumigene assay 93.3 %, 99.7 %, 95.8 % and 99.5 %. Illumigene assays performed significantly better for non-014/020 PCR-ribotypes than for C. difficile isolates belonging to 014/020. Discrepant analysis of three culture-negative, but Illumigene-positive samples, revealed the presence of toxin genes using real-time PCRs. In addition to the GDH EIA (NPV of 99.8 %), the performance of Illumigene allows this test to be introduced as a first screening test for CDI- or as a confirmation test for GDH -positive samples, although the initial invalid Illumigene result of 4.4 % is a point of concern.