Laboratory diagnosis of Clostridium difficile-associated diarrhoea: a plea for culture

Ribotyping of Clostridioides difficile in the Liberec Regional Hospital: a tertiary health care facility

The ribotyping of Clostridioides difficile is one of the basic methods of molecular epidemiology for monitoring the spread of C. difficile infections. In the Czech Republic, this procedure is mainly available in university hospitals. The introduction of ribotyping in a tertiary health care facility such as Liberec Regional Hospital not only increases safety in the facility but also supports regional professional development. In our study, 556 stool samples collected between June 2017 and June 2018 were used for C. difficile infection screening, followed by cultivation, toxinotyping, and ribotyping of positive samples. The toxinotyping of 96 samples revealed that 44.8% of typed strains could produce toxins A and B encoded by tcdA and tcdB, respectively. The ribotyping of the same samples revealed two epidemic peaks, caused by the regionally most prevalent ribotype 176 (n = 30, 31.3). C. difficile infection incidence ranged between 5.5 and 4.2 cases per 10,000 patient-bed days. Molecular diagnostics and molecular epidemiology are the two most developing parts of clinical laboratories. The correct applications of molecular methods help ensure greater safety in hospitals.

Elephant Endotheliotropic Herpesvirus 4 and Clostridium perfringens Type C Fatal Co-Infection in an Adult Asian Elephant (Elephas maximus)

Elephant endotheliotropic herpesvirus hemorrhagic disease (EEHV-HD) is an acute, often fatal, multisystemic hemorrhagic disease and one of the most significant causes of mortality of Asian elephants in captivity. Most fatal cases of EEHV-HD are associated with EEHV1A and EEHV1B in juveniles. This case report describes the clinical and pathological features of a fatal co-infection of Clostridium perfringens type C and EEHV-HD, caused by EEHV4, in an adult female Asian elephant. Although fatal clostridial enterotoxemia has been occasionally reported in elephants, this report highlights the importance of having both EEHV-HD and clostridial enterotoxemia as potential differential diagnoses in cases of widespread tissue necrosis and internal hemorrhage in elephants, regardless of the animal age group, due to their macroscopic similarities, frequent co-occurrence and cumulative morbid potential.

Clostridioides difficile: Current overview and future perspectives

The most common world-wide cause of antibiotic-associated infectious diarrhea and colitis is the toxin producing bacterium, Clostridioides difficile (C. difficile). Here we review the background and characteristics of the bacterium and the toxins produced together with the epidemiology and the complex pathogenesis that leads to a broad clinical spectrum of disease. The review describes the difficulties faced in obtaining a quick and accurate diagnosis despite the range of sensitive and specific diagnostic tools available. We also discuss the problem of disease recurrence and the importance of disease prevention. The high rates of infection recurrence mean that treatment strategies are constantly under review and we outline the diverse treatment options that are currently in use and explore the emerging treatment options of pulsed antibiotic use, microbial replacement therapies and the use of monoclonal antibodies. We summarize the future direction of treatment strategies which include the development of novel antibiotics, the administration of oral polyclonal antibody formulations, the use of vaccines, the administration of competitive non-toxigenic spores and the neutralization of antibiotics at the microbiota level. Future successful treatments will likely involve a combination of therapies to provide the most effective and robust approach to C. difficile management.

Pragmatic Strategy for Fecal Specimen Storage and the Corresponding Test Methods for Clostridioides difficile Diagnosis

The quality of fecal specimens is one of the factors responsible for successful Clostridioides difficile infection (CDI) diagnosis. The quality depends largely on the storage conditions, including the temperature and time period. In this study, we organized the outputs of previous studies, filled experimental gaps in the knowledge of storage conditions, and introduced a pragmatic strategy for fecal storage for CDI diagnosis. A 5-step pathway was adopted to develop the fecal specimen storage strategy as follows: step 1, bibliomic analysis; step 2, experimental gap-filling; step 3, comparative evaluation; step 4, strategy development; step 5, internal review. Step 1 identified eight articles providing experimental information on the effects of fecal specimen storage conditions on the effectiveness of C. difficile detection methods. Step 2 provided additional quantitative data on C. difficile vegetative and spore cell viability and DNA stability. All previous and current results were compared (step 3). In step 4, fir general and nine special strategies were developed, followed by an internal review of the overall approaches (step 5). It is recommended to separate fecal samples into aliquots before testing and storing them. It is particularly recommended that fecal specimen samples be stored for CDI diagnosis at 4 °C for up to 60 days for all test methods.

Use of culture- and ELISA-based toxin assay for detecting Clostridium Difficile, a neglected pathogen: A single-center study from a tertiary care setting

INTRODUCTION:

Clostridium difficile is a Gram-positive spore-bearing anaerobic bacillus increasingly associated with both community- and hospital-acquired colitis and diarrhea. It is the most common identifiable bacterial cause of healthcare-associated diarrhea associated with antibiotic use and one of the most common anaerobic infections. The diagnosis of C. difficile infection includes detection of toxin A/B in stool specimens by direct enzyme immunoassay, culture of pathogen from the stool specimens using a selective agar Cycloserine-Cefoxitin fructose agar (CCFA), tissue culture assay, and detection of glutamate dehydrogenase an enzyme produced by C. difficile. With few reports from India on this disease, the present study was planned to throw more light on the prevalence and utility of laboratory diagnostic methods for C. difficile-associated diarrhea (CDAD).

MATERIAL AND METHODS:

After taking approval from the Ethics Committee, 150 patients with antibiotic-associated diarrhea were taken as a study group and fifty patients with exposure to antibiotics but who did not develop diarrhea were taken as controls. Stool specimen was processed for both culture on CCFA and toxin detection by IVD Tox A + B ELISA.

RESULTS:

Only four specimens were culture positive, whereas 13 were ELISA positive. All culture-positive isolates were toxigenic. C. difficile was neither isolated nor its toxin detected in the control group. Culture- and toxin-based assays may not detect all cases of CDAD.

CONCLUSION:

Based on the results of the present study, culture does not provide any additional yield over toxin assay. Better diagnostic modalities would be required to prove CDAD.

Seasonality of Clostridium difficile in the natural environment

Clostridium difficile is considered the leading cause of antibiotic-associated disease worldwide. In the past decade, a large number of studies have focused on identifying the main sources of contamination in order to elucidate the complete life cycle of the infection. Hospitals, animals and retail foods have been considered as potential vectors. However, the prevalence of C. difficile in these types of samples was found to be rather low, suggesting that other contamination routes must exist. This study explores the presence of C. difficile in the natural environment and the seasonal dynamics of the bacterium. C. difficile was isolated from a total of 45 samples out of 112 collected (40.2%) on 56 sampling points. A total of 17 points were positive only during the winter sampling (30.4%), 10 were positive only during the summer sampling (17.9%) and 9 sampling points (16.1%) were positive in both summer sampling and winter sampling. Spore counts in soil samples ranged between 50 and 250 cfu/g for 24.4% of the positive samples, with the highest concentrations detected in samples collected in the forest during winter campaign (200-250 cfu/g). A total of 17 different PCR ribotypes were identified, and 15 of them had the genes coding for toxins A and B. Most of those ribotypes had not previously been found or had been isolated only sporadically (<1% of samples) from hospitals in Belgium. Regarding antimicrobial susceptibility, most of the resistant strains were found during the summer campaign. These findings bear out that C. difficile is present in the natural environment, where the bacterium undergoes seasonal variations.

Clostridium difficile beyond stools: dog nasal discharge as a possible new vector of bacterial transmission

Zoonotic transmission of Clostridium difficile has been largely hypothesised to occur after direct or indirect contact with contaminated animal faeces. Recent studies have reported the presence of the bacterium in the natural environment, including in soils and rivers. If C. difficile spores are scattered in the environment, they can easily enter the respiratory tract of dogs, and therefore, dog nasal discharge could be a direct route of transmission not previously investigated. This study reports for the first time the presence of C. difficile in the respiratory tracts of dogs. The bacterium was isolated from 6 (17.1%) out of 35 nasal samples, with a total of 4 positive dogs (19%). C. difficile was recovered from both proximal and distal nasal cavities. All isolates were toxigenic and belonged to PCR-ribotype 014, which is one of the most predominant types in animals and in community-acquired C. difficile infections in recent years. The findings of this study demonstrate that the nasal cavity of dogs is contaminated with toxigenic C. difficile, and therefore, its secretions could be considered as a new route by which bacteria are spread and transmitted.

Rapid, label-free genetic detection of enteropathogens in stool without genetic isolation or amplification

Current genetic detection methods require gene isolation, gene amplification and detection with a fluorescent-tagged probe. They typically require sophisticated equipment and expensive fluorescent probes, rendering them not widely available for rapid acute infection diagnoses at the point of care to ensure timely treatment of the diseases. Here we report a rapid genetic detection method that can detect the bacterial gene directly from patient stools using a piezoelectric plate sensor (PEPS) in conjunction with a continuous flow system with two temperature zones. With stools spiked with sodium dodecyl sulfate (SDS) in situ bacteria lysing and DNA denaturation occurred in the high-temperature zone whereas in situ specific detection of the denatured DNA by the PEPS occurred in the lower-temperature zone. The outcome was a rapid genetic detection method that directly detected bacterial genes from stool in < 40 min without the need of gene isolation, gene amplification, or expensive fluorescent tag but with polymerase chain reaction (PCR) sensitivity. In 40 blinded patient stools, it detected the toxin B gene of Clostridium difficile with 95% sensitivity and 95% specificity. The all-electrical, label-free nature of the detection further supports its potential as a low-cost genetic test that can be used at the point of care.

Toxigenic Clostridium difficile isolates from clinically significant diarrhoea in patients from a tertiary care centre

Background & objectives:

Clostridium difficile is the primary cause of hospital-acquired colitis in patients receiving antibiotics. The pathogenicity of the organism is mainly due to the production of toxins. This study was conducted to investigate the presence of toxigenic C. difficile in the faecal samples of hospitalized patients suspected to have C. difficile infection (CDI) and corroborating the findings with their clinical and demographic data.

Methods:

Diarrhoeic samples obtained from 1110 hospitalized patients were cultured for C. difficile and the isolates confirmed by phenotypic and molecular methods. Toxigenicity of the isolates was determined using enzyme-linked immunosorbent assay for toxins A and B. Details of patients included in the study were noted and analyzed.

Results:

Of the 1110 patients (mean age 39±19.6 yr), 63.9 per cent were males and 36.1 per cent were females. The major antibiotics received by the patients were nitazoxanide (23.9%), penicillins/penicillin combinations (19.0%), quinolones including fluoroquinolones (13.1%), carbapenems (11.5%), glycopeptides (11.0%) and cephalosporins (8.4%). The clinical symptoms predominantly present were watery diarrhoea (56.4%), fever (40.0%) and abdominal pain (35.3%). The underlying diseases were gastrointestinal disorders (52.6%), followed by cancers (13.2%), surgical conditions (8.3%), and hepatic disorders (8.0%). Of the 174 C. difficile isolates, 54.6 per cent were toxigenic. Toxigenic C. difficile was present in all patients with surgical conditions, 65.2 per cent with cancers and 57.1 per cent with gastrointestinal disorders.

Interpretation & conclusions:

C. difficile was found to be an important cause of gastrointestinal infections in hospitalized patients with underlying diseases and on antibiotics. Clinical conditions of the patients correlating with toxigenic culture can be an important tool for establishing CDI diagnosis.

Characterization of Clostridium difficile Strains Isolated from Patients with C. difficile-associated Disease in Korea

Objectives

Studies on Clostridium difficile are rare in Korea. We investigated the epidemiological characteristics of C. difficile isolates from patients with C. difficile-associated disease (CDAD) in Korea.

Methods

Multiplex polymerase chain reaction was performed to detect the presence of tcdA and tcdB toxin genes. Antimicrobial susceptibility test was carried out by the disk-dilution method. C. difficile strains were subtyped by automated repetitive-element palindromic PCR (rep-PCR).

Results

Among patients with CDAD, 73 (25.8%), 32 (11.3%), 32 (11.3%), and 26 (9.2%) suffered from pneumonia, cancer or neoplasm, diabetes, and colitis, respectively. Of all stool samples, 43 samples (15.2%) were positive for C. difficile strains. We observed two expression patterns of toxin genes: tcdA+/tcdB+ (86% isolates) and tcdA-/tcdB+ (14% isolates), with all isolates expressing tcdB. Furthermore, some isolates were resistant to clindamycin (65%), ampicillin (56%), and cefazolin (40%), but all were susceptible to vancomycin and metronidazole. The tested samples were classified into diverse clusters using automated rep-PCR.

Conclusion

Our findings revealed the characteristics and antibiotic resistance of C. difficile isolates from patients in Korea. The epidemiological data may provide valuable insight into development of treatment strategies for C. difficile infections in Korea.

A Decade of Development of Chromogenic Culture Media for Clinical Microbiology in an Era of Molecular Diagnostics

In the last 25 years, chromogenic culture media have found widespread application in diagnostic clinical microbiology. In the last decade, the range of media available to clinical laboratories has expanded greatly, allowing specific detection of additional pathogens, including Pseudomonas aeruginosa, group B streptococci, Clostridium difficile, Campylobacter spp., and Yersinia enterocolitica. New media have also been developed to screen for pathogens with acquired antimicrobial resistance, including vancomycin-resistant enterococci, carbapenem-resistant Acinetobacter spp., and Enterobacteriaceae with extended-spectrum β-lactamases and carbapenemases. This review seeks to explore the utility of chromogenic media in clinical microbiology, with particular attention given to media that have been commercialized in the last decade. The impact of laboratory automation and complementary technologies such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is also assessed. Finally, the review also seeks to demarcate the role of chromogenic media in an era of molecular diagnostics.

Optimizing the diagnostic testing of Clostridium difficile infection

INTRODUCTION

Clostridium difficile infection (CDI) is the leading cause of hospital-acquired diarrhea and is associated with a considerable health and cost burden. However, there is still not a clear consensus on the best laboratory diagnosis approach and a wide variation of testing methods and strategies can be encountered.

AREAS COVERED

We aim to review the most practical aspects of CDI diagnosis providing our own view on how to optimize CDI diagnosis. Expert commentary: Laboratory diagnosis in search of C. difficile toxins should be applied to all fecal diarrheic samples reaching the microbiology laboratory in patients > 2 years old, with or without classic risk factors for CDI. Detection of toxins either directly in the fecal sample or in the bacteria isolated in culture confirm CDI in the proper clinical setting. Nuclear Acid Assay techniques (NAAT) allow to speed up the process with epidemiological and therapeutic consequences.

Clostridium difficile Infections in Children: Impact of the Diagnostic Method on Infection Rates

BACKGROUND

Polymerase chain reaction (PCR) assays based on the detection of the toxin B gene are replacing enzyme-linked immunosorbent assay (ELISA)–based toxin production detection or cell cytotoxicity assay in most laboratories.

OBJECTIVE

To determine the proportion of pediatric patients diagnosed withClostridium difficile infection by PCR who would have also been diagnosed by ELISA and to compare the clinical characteristics of PCR+/ELISA+ vs PCR+/ELISA− patients.

METHODS

Using the microbiology laboratory information system, stool samples positive for C. difficile by PCR between October 2010 and July 2014 were identified. Using frozen stool specimens, an ELISA for toxin A and B was performed. A retrospective medical chart review was conducted to obtain demographic and clinical data. Duplicate samples were excluded.

RESULTS

A total of 136 PCR-positive samples underwent ELISA testing: 54 (40%) were positive for toxin A or B. The mean (SD) age of the entire cohort was 8.5 (6.2) years. There was no difference in age, gender, clinical manifestation, previous medical problems, and management between patients positive or negative by ELISA. However, patients positive by ELISA were more likely to have had a recent exposure to antibiotics (67.9% vs 50%; crude odds ratio, 2.1 [95% CI, 1.03–4.28]).

CONCLUSION

In our pediatric population, 60% of patients with C. difficile diagnosed by PCR had no toxin detectable by ELISA. ELISA-negative patients were less likely to have received an antibiotic recently compared with ELISA-positive patients. These results highlight the need to standardize laboratory criteria for the diagnosis of C. difficile infections in children.

Infect Control Hosp Epidemiol 2016;37:1087–1093

Sensitive quantification of Clostridium perfringens in human feces by quantitative real-time PCR targeting alpha-toxin and enterotoxin genes

BACKGROUND

Clostridium perfringens is a widespread pathogen, but the precise quantification of this subdominant gut microbe remains difficult due to its low fecal count (particularly in asymptomatic subjects) and also due to the presence of abundant polymerase-inhibitory substances in human feces. Also, information on the intestinal carriage of toxigenic C. perfringens strains in healthy subjects is sparse. Therefore, we developed a sensitive quantitative real-time PCR assays for quantification of C. perfringens in human feces by targeting its α-toxin and enterotoxin genes. To validate the assays, we finally observed the occurrence of α-toxigenic and enterotoxigenic C. perfringens in the fecal microbiota of healthy Japanese infants and young adults.

METHODS

The plc-specific qPCR assay was newly validated, while primers for 16S rRNA and cpe genes were retrieved from literature. The assays were validated for specificity and sensitivity in pre-inoculated fecal samples, and were finally applied to quantify C. perfringens in stool samples from apparently healthy infants (n 124) and young adults (n 221).

RESULTS

The qPCR assays were highly specific and sensitive, with a minimum detection limit of 10(3) bacterial cells/g feces. Alpha-toxigenic C. perfringens was detected in 36% infants and 33% adults, with counts ranging widely (10(3)-10(7) bacterial cells/g). Intriguingly, the mean count of α-toxigenic C. perfringens was significantly higher in infants (6.0±1.5 log10 bacterial cells/g), as compared to that in adults (4.8±1.2). Moreover, the prevalence of enterotoxigenic C. perfringens was also found to be significantly higher in infants, as compared to that in adults. The mean enterotoxigenic C. perfringens count was 5.9±1.9 and 4.8±0.8 log10 bacterial cells/g in infants and adults, respectively.

CONCLUSIONS

These data indicate that some healthy infants and young adults carry α-toxigenic and enterotoxigenic C. perfringens at significant levels, and may be predisposed to related diseases. Thus, high fecal carriage of toxigenic C. perfringens in healthy children warrants further investigation on its potential sources and clinical significance in these subjects. In summary, we present a novel qPCR assay for sensitive and accurate quantification of α-toxigenic and enterotoxigenic C. perfringens in human feces, which should facilitate prospective studies of the gut microbiota.

Low sensitivity of fecal toxin A/B enzyme immunoassay for diagnosis of Clostridium difficile infection in immunocompromised patients

The optimal approach in laboratory diagnosis of Clostridium difficile infection (CDI) is still not well defined. Toxigenic culture (TC) or alternatively fecal toxin assay by cell cytotoxicity neutralization assay are considered to be the reference standard, but these methods are time-consuming and labor intensive. In many medical centers, diagnosis of CDI is therefore still based on fecal toxin A/B enzyme immunoassay (EIA) directly from stool alone, balancing cost and speed against limited diagnostic sensitivity. The aim of the study was to assess in which patient population the additional workload of TC is justified. All consecutive stool specimens submitted for diagnosis of suspected CDI between 2004 and 2011 at a tertiary-care center were examined by toxin EIA and TC. Clinical data of patients with established diagnosis of CDI were collected in a standardized case-report form. From 12,481 stool specimens submitted to the microbiologic laboratory, 480 (3.8%) fulfilled CDI criteria; 274 (57.1%) were diagnosed by toxin EIA; and an additional 206 (42.9%) were diagnosed by TC when toxin EIA was negative. Independent predictors for negative toxin EIA but positive TC were high-dose corticosteroids (odds ratio (OR) 2.97, 95% confidence interval (CI) 1.50-5.90, p 0.002), leukocytopenia <1000/μL (OR 2.52, 95% CI 1.22-5.23, p 0.013) and nonsevere CDI (OR 2.21, 95% CI 1.39-3.50, p 0.001). There was no difference in outcomes such as in-hospital mortality and recurrence between both groups. In conclusion, negative toxin EIA does not rule out CDI in immunocompromised patients in the setting of relevant clinical symptoms. Methods with improved sensitivity such as TC or PCR should be used, particularly in this patient population.

Epidemiology and clinical features of toxigenic culture-confirmed hospital-onset Clostridium difficile infection: a multicentre prospective study in tertiary hospitals of South Korea

Hypervirulent Clostridium difficile strains, most notably BI/NAP1/027, have been increasingly emerging in Western countries as local epidemics. We performed a prospective multicentre observational study from December 2011 to May 2012 to identify recent incidences of toxigenic culture-confirmed hospital-onset C. difficile infections (CDI) and their associated clinical characteristics in South Korea. Patients suspected of having been suffering from CDI more than 48 h after admission and aged ≥20 years were prospectively enrolled and provided loose stool specimens. Toxigenic C. difficile culture (anaerobic culture+toxin A/B/binary gene PCR) and PCR ribotyping were performed in one central laboratory. We enrolled 98 toxigenic culture-confirmed CDI-infected patients and 250 toxigenic culture-negative participants from three hospitals. The incidence of toxigenic culture-confirmed hospital-onset CDI cases was 2.7 per 10,000 patient-days. The percentage of severe CDI cases was relatively low at only 3.1%. UK ribotype 018 was the predominant type (48.1%). There were no hypervirulent BI/NAP1/027 isolates identified. The independent risk factors for toxigenic culture-confirmed hospital-onset CDI were invasive procedure (odds ratio (OR) 7.3, P=0.003) and past CDI history within 3 months (OR 28.5, P=0.003). In conclusion, the incidence and severity of CDI in our study were not higher than reported in Western countries.

Performance of chromID Clostridium difficile agar compared with BBL C. difficile selective agar for detection of C. difficile in stool specimens

We evaluated the performance of a new chromogenic medium for detection of Clostridium difficile, chromID C. difficile agar (CDIF; bioMérieux, France), by comparison with BBL C. difficile Selective Agar (CDSA; Becton Dickinson and Company, USA). After heat pre-treatment (80℃, 5 min), 185 diarrheal stool samples were inoculated onto the two media types and incubated anaerobically for 24 hr and 48 hr for CDIF and for 48 hr and 72 hr for CDSA. All typical colonies on each medium were examined by Gram staining, and the gram-positive rods confirmed to contain the tpi gene by PCR were identified as C. difficile. C. difficile was recovered from 36 samples by using a combination of the two media. The sensitivity with CDIF 48 hr was highest (100%) and was significantly higher than that with CDIF 24 hr (58.3%; P<0.001), because samples with a low burden of C. difficile tended to require prolonged incubation up to 48 hr (P<0.001). The specificity of CDIF 24 hr and CDIF 48 hr (99.3% and 90.6%, respectively) was significantly higher than that of CDSA 48 hr and CDSA 72 hr (72.5% and 67.1%, respectively; P<0.001). CDIF was effective for detecting C. difficile in heat-pretreated stool specimens, thus reducing unnecessary testing for toxin production in non-C. difficile isolates and turnaround time.

Detection of Clostridium difficile diarrhoea in Harare, Zimbabwe

BACKGROUND

Clostridium difficile is associated with nosocomial and community-acquired diarrhoea and pseudomembranous colitis in humans. Little information is available on the importance of C. difficile as a causative agent of diarrhoea in developing countries such as Zimbabwe. The current study was carried out to determine the prevalence of C. difficile in diarrhoeal stools of outpatients over 2 years of age presenting at healthcare centres in Harare, Zimbabwe, and to determine the antimicrobial susceptibility of the isolates.

METHODS

Toxigenic stool culture was used in this study. Diarrhoeal stool specimens were cultured for C. difficile, followed by direct immunoassay on colonies of positive cultures with significant growth to detect toxins A or B.

RESULTS

C. difficile was detected in 8.6% (n=23) of the 268 diarrhoeal stool specimens. All C. difficile isolates were susceptible to metronidazole, vancomycin, chloramphenicol and doxycyline, and resistant to clindamycin, ciprofloxacin, gentamicin and cefotaxime. About 70% of the isolates were resistant to co-trimoxazole.

CONCLUSIONS

C. difficile was observed to be an important diarrhoeal pathogen and metronidazole was effective in treating diarrhoea caused by the bacterium. Co-trimoxazole, which is widely used as prophylaxis against opportunistic infections in HIV/AIDS patients, was not very effective in preventing diarrhoea caused by C. difficile.

Economic evaluation of laboratory testing strategies for hospital-associated Clostridium difficile infection

Clostridium difficile infection (CDI) is the most common cause of infectious diarrhea in health care settings, and for patients presumed to have CDI, their isolation while awaiting laboratory results is costly. Newer rapid tests for CDI may reduce this burden, but the economic consequences of different testing algorithms remain unexplored. We used decision analysis from the hospital perspective to compare multiple CDI testing algorithms for adult inpatients with suspected CDI, assuming patient management according to laboratory results. CDI testing strategies included combinations of on-demand PCR (odPCR), batch PCR, lateral-flow diagnostics, plate-reader enzyme immunoassay, and direct tissue culture cytotoxicity. In the reference scenario, algorithms incorporating rapid testing were cost-effective relative to nonrapid algorithms. For every 10,000 symptomatic adults, relative to a strategy of treating nobody, lateral-flow glutamate dehydrogenase (GDH)/odPCR generated 831 true-positive results and cost $1,600 per additional true-positive case treated. Stand-alone odPCR was more effective and more expensive, identifying 174 additional true-positive cases at $6,900 per additional case treated. All other testing strategies were dominated by (i.e., more costly and less effective than) stand-alone odPCR or odPCR preceded by lateral-flow screening. A cost-benefit analysis (including estimated costs of missed cases) favored stand-alone odPCR in most settings but favored odPCR preceded by lateral-flow testing if a missed CDI case resulted in less than $5,000 of extended hospital stay costs and <2 transmissions, if lateral-flow GDH diagnostic sensitivity was >93%, or if the symptomatic carrier proportion among the toxigenic culture-positive cases was >80%. These results can aid guideline developers and laboratory directors who are considering rapid testing algorithms for diagnosing CDI.

Correlation between Clostridium difficile bacterial load, commercial real-time PCR cycle thresholds, and results of diagnostic tests based on enzyme immunoassay and cell culture cytotoxicity assay

The impact of Clostridium difficile fecal loads on diagnostic test results is poorly understood, but it may have clinical importance. In this study, we investigated the relationship between C. difficile fecal load and the results of four assays: a glutamate dehydrogenase (GDH) enzyme immunoassay (EIA), a toxin A/B antigen EIA (ToxAB), a cell culture cytotoxicity assay (CCA), and PCR targeting the tcdB gene. We also compared the PCR cycle threshold (CT) with the results of quantitative culture using Spearman's rank correlation coefficient. Finally, we sequenced the genomes of 24 strains with different detection profiles. A total of 203 clinical samples harboring toxigenic C. difficile were analyzed and sorted into one of four groups: 17 PCR(+) (group 1), 37 PCR(+) GDH(+) (group 2), 24 PCR(+) GDH(+) CCA(+) (group 3), and 125 PCR(+) GDH(+) ToxAB(+) (group 4). The overall median fecal load in log10 CFU/g was 6.67 (interquartile range [IQR], 5.57 to 7.54). The median fecal bacterial load of groups 1, 2, 3, and 4 were 4.15 (IQR, 3.00 to 4.98), 5.74 (IQR, 4.75 to 6.16), 6.20 (IQR, 5.23 to 6.80), and 7.08 (IQR, 6.35 to 7.83), respectively. Group 1 samples had lower fecal loads than those from each of the other groups (P < 0.001). Group 2 samples had lower fecal loads than those from groups 3 and 4 (P < 0.001). There was a significant correlation between PCR CT and fecal loads (ρ = -0.697; P < 0.001). NAP1 strains were associated with the detection of toxins by EIA or CCA (P = 0.041). This study demonstrates an association between C. difficile fecal load and the results of routinely used diagnostic tests.

Evaluation of cycloserine-cefoxitin fructose agar (CCFA), CCFA with horse blood and taurocholate, and cycloserine-cefoxitin mannitol broth with taurocholate and lysozyme for recovery of Clostridium difficile isolates from fecal samples

Cycloserine-cefoxitin fructose agar (CCFA), CCFA with horse blood and taurocholate (CCFA-HT), and cycloserine-cefoxitin mannitol broth with taurocholate and lysozyme (CCMB-TAL) were compared for recovery of Clostridium difficile from 120 stool specimens. Compared to CCFA, CCFA-HT enhanced C. difficile growth and improved recovery by 4%. In a separate study, 9% (8/91) of stool samples previously C. difficile negative on plate medium were C. difficile positive when cultured in CCMB-TAL.

Evaluation of multiplex PCR with enhanced spore germination for detection of Clostridium difficile from stool samples of the hospitalized patients

Clostridium difficile poses as the most common etiologic agent of nosocomial diarrhea. Although there are many diagnostic methods to detect C. difficile directly from stool samples, the nucleic acid-based approach has been largely performed in several laboratories due to its high sensitivity and specificity as well as rapid turnaround time. In this study, a multiplex PCR was newly designed with recent accumulated nucleotide sequences. The PCR testing with various C. difficile ribotypes, other Clostridium spp., and non-Clostridium strains revealed 100% specificity with the ability to detect as low as ~22 genomic copy number per PCR reaction. Different combinations of sample processing were evaluated prior to multiplex PCR for the detection of C. difficile in fecal samples from hospitalized patients. The most optimal condition was the non-selective enrichment at 37°C for 1 h in brain heart infusion broth supplemented with taurocholate, followed by the multiplex PCR. The detection limit after sample processing was shown as being 5 spores per gram of fecal sample. Two hundred and thirty-eight fecal samples collected from the University affiliated hospital were analyzed by the enrichment multiplex PCR procedure. The results suggested that the combination of sample processing with the high-performance detection method would be applicable for routine diagnostic use in clinical setting.

Outcomes in patients tested for Clostridium difficile toxins

Clostridium difficile testing is shifting from toxin detection to C. difficile detection. Yet, up to 60% of patients with C. difficile by culture test negative for toxins and it is unclear whether they are infected or carriers. We reviewed medical records for 7046 inpatients with a C. difficile toxin test from 2005 to 2009 to determine the duration of diarrhea and rate of complications and mortality among toxin-positive (toxin+) and toxin- patients. Overall, toxin- patients had less severe diarrhea, fewer diarrhea days, and lower mortality (P < 0.001, all comparisons) than toxin+ patients. One toxin- patient (n = 1/6121; 0.02%) was diagnosed with pseudomembranous colitis, but there were no complications such as megacolon or colectomy for fulminant CDI among toxin- patients. These data suggest that C. difficile-attributable complications are rare among patients testing negative for C. difficile toxins. More studies are needed to evaluate the clinical significance of C. difficile detection in toxin- patients.

Comparison of a frozen human foreskin fibroblast cell assay to an enzyme immunoassay and toxigenic culture for the detection of toxigenic Clostridium difficile

This study set out to validate the Hs27 ReadyCell assay (RCCNA) as an alternative CCNA method compared against a commonly used commercial enzyme immunoassay (EIA) method and toxigenic culture (TC) reference standard. A total of 860 samples were identified from those submitted to the Health Protection Agency microbiology laboratories over a 30-week period. RCCNA performed much better than EIA when using TC as a gold standard, with sensitivities of 90.8% versus 78.6% and positive predictive value of 87.3% to 81.9%, respectively. The Hs27 Human Foreskin Fibroblast ReadyCells are an easy-to-use and a sensitive CCNA method for the detection of toxigenic Clostridium difficile directly from stool. A turnaround time of up to 48 h for a negative result and possible need for repeat testing make it an unsuitable method to be used in most clinical laboratory setting.

Clostridium difficile in young farm animals and slaughter animals in Belgium

Faecal carriage of Clostridium difficile in healthy animals has been reported recently, especially in piglets and calves. However there is limited data about carriage in animals just prior to slaughter in Europe. The main objective of this study was to determine the presence of C. difficile in pigs and cattle at the slaughterhouse. C. difficile was isolated in 6.9% of the cattle at the slaughterhouse. None of the pig slaughter samples were positive for C. difficile after an enrichment time of 72 h. For complementary data, a short study was conducted in piglets and calves at farms. C. difficile was more prevalent in piglets (78.3%) than in calves (22.2%) on the farms. Regarding the piglet samples, 27.8% of the positive samples were detected without enrichment of stools. The PCR ribotype 078 was predominant in farm animals. Samples isolated from slaughter cattle presented the widest range in PCR-ribotype variety, and the most prevalent PCR ribotype was 118a UCL. The results of this study confirm that C. difficile is present in slaughter animals in Belgium with a large percentage of toxigenic strains also commonly found in humans.

Comparison of antigen and two molecular methods for the detection of Clostridium difficile toxins

BACKGROUND

Clostridium difficile (CD) is considered an important cause of diarrhoea associated with the antimicrobial treatment of infections. The pathogenicity of CD is due to toxins A and B, produced by toxigenic CD strains.

METHODS

We evaluated 3 methods for detecting CD toxins: the RIDASCREEN® enzyme immunoassay (EIA) (R-Biopharm)--one detecting toxins directly in the stool specimens and another detecting toxins from isolated CD strains--and 2 molecular methods, the illumigene™ loop-mediated isothermal amplification (LAMP) assay (Meridian) and RIDA®GENE polymerase chain reaction (PCR) assay (R-Biopharm), as direct identification methods from stool specimens. Toxigenic culture (TC) was used as the reference method.

RESULTS

Altogether 884 stool samples were analyzed, of which 253 (29%) were positive by TC. Six hundred and seventy-two specimens were tested by RIDASCREEN EIA, 430 were tested with the illumigene LAMP assay, and 212 were tested with the RIDA GENE PCR assay. CD toxin A and B antigen tests by EIA were very insensitive, both directly from stool specimens (2 series; 57-61%) and in isolated CD strains (53%); consequently the negative predictive value remained low (84-93% and 91%, respectively). Specificity, however, was very good at 98-100%. The 2 molecular methods detected CD toxin genes excellently and equally, resulting in sensitivities, specificities, and positive and negative predictive values of 98%, 100%, 100%, and 98%, respectively.

CONCLUSIONS

Both molecular assays were easy to use, rapid, sensitive, and specific for the detection of toxigenic CD strains.

Improved recovery of Clostridium difficile spores with the incorporation of synthetic taurocholate in cycloserine-cefoxitin-fructose agar (CCFA)

AIM

Culture remains important for the detection and typing of Clostridium difficile. Culture of C. difficile spores can be enhanced on media supplemented with a germinant. Despite this, unsupplemented media continues to be used in some laboratories. The aim of this study was to quantify the effect of the known germinant sodium taurocholate on recovery of C. difficile spores and to determine if the supplement impacts on the recovery of vegetative C. difficile.

METHODS

The recovery on cycloserine-cefoxitin-fructose agar (CCFA) with and without taurocholate, of spore, vegetative, and total cell fractions of broth cultures of eight C. difficile isolates was compared.

RESULTS

Taurocholate in CCFA did not inhibit growth of vegetative C. difficile and significantly increased recovery of spores (p = 0.04).

CONCLUSIONS

The routine incorporation of taurocholate in CCFA is recommended for improved sensitivity in C. difficile culture from specimens.

Comparison of BD GeneOhm Cdiff and Seegene Seeplex ACE PCR assays using toxigenic Clostridium difficile culture for direct detection of tcdB from stool specimens

We evaluated the performances of 2 PCR assays (BD GeneOhm and Seegene ACE) for direct detection of tcdB from stool specimens. The concordance rate between BD and Seegene was 96.3%. The sensitivities, specificities, positive predictive values (PPVs), and negative predictive values (NPVs) of BD and Seegene were 95.7%, 96.5%, 91.8%, and 98.2% and 90.0%, 97.1%, 92.6%, and 96.0%, respectively.

Role of fecal Clostridium difficile load in discrepancies between toxin tests and PCR: is quantitation the next step in C. difficile testing?

Direct tests for Clostridium difficile are 30-50 % more sensitive than tests for C. difficile toxins but the reasons for this discrepancy are incompletely understood. In addition to toxin degradation and strain differences, we hypothesized that C. difficile concentration could be important in determining whether toxins are detected in fecal samples. We performed standard curves on an FDA-approved real-time PCR test for the C. difficile tcdB gene (Xpert C. difficile/Epi, Cepheid) during a prospective comparison of a toxin immunoassay (Meridian Premier), PCR and toxigenic culture. Immunoassay-negative, PCR-positive samples were retested with a cell cytotoxin assay (TechLab). Among 107 PCR-positive samples, 46 (43.0 %) had toxins detected by immunoassay and an additional 18 (16.8 %) had toxin detected by the cytotoxin assay yielding 64 (59.8 %) toxin-positive and 43 (40.2 %) toxin-negative samples. Overall, toxin-negative samples with C. difficile had 10(1)-10(4) fewer DNA copies than toxin-positive samples and most discrepancies between toxin tests and PCR were associated with a significant difference in C. difficile quantity. Of the toxin-positive samples, 95 % had ≥ 4.1 log(10) C. difficile tcdB DNA copies/mL; 52 % of immunoassay-negative samples and 70 % of immunoassay and cytotoxin negative samples had <4.1 log(10) C. difficile tcdB DNA copies/mL. These findings suggest that fecal C. difficile concentration is a major determinant of toxin detection and C. difficile quantitation may add to the diagnostic value of existing test methods. Future studies are needed to validate the utility of quantitation and determine the significance of low concentrations of C. difficile in the absence of detectable toxin.

Molecular techniques for diagnosis of Clostridium difficile infection: systematic review and meta-analysis

OBJECTIVE

To assess the usefulness of 2 rapid molecular diagnostic techniques, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP), in Clostridium difficile infection (CDI).

METHODS

We conducted a systematic review and meta-analysis to evaluate the accuracy of PCR and LAMP in diagnosis of CDI, including studies that used toxigenic culture or cytotoxicity assay as reference standard.

RESULTS

A search of PubMed and CinAHL medical databases yielded 25 PCR studies, including 11,801 samples that met inclusion criteria and 6 heterogeneous studies that evaluated LAMP. With toxigenic culture as a standard, pooled sensitivity was 0.92 (95% confidence interval [CI], 0.91-0.94); specificity, 0.94 (95% CI, 0.94-0.95); and diagnostic odds ratio, 378 (95% CI, 260-547). With cytotoxicity as a standard, pooled sensitivity was 0.87 (95% CI, 0.84-0.90); specificity, 0.97 (95% CI, 0.97-0.98); and diagnostic odds ratio, 370 (95% CI, 226-606).

CONCLUSION

Polymerase chain reaction is a highly accurate test for identifying CDI. Heterogeneity in LAMP studies did not allow meta-analysis; however, further research into this promising method is warranted.

A Clostridium difficile infection "intervention": change in toxin assay results in fewer C difficile infection cases without changes in patient outcomes

BACKGROUND

Clostridium difficile infection (CDI) is most commonly diagnosed using toxin enzyme immunoassays (EIAs). A sudden decrease in CDI incidence was noted after a change in the EIA used at Barnes-Jewish Hospital in St Louis. The objective of this study was to determine whether the decreased CDI incidence related to the change in EIA resulted in adverse patient outcomes.

METHODS

Electronic hospital databases were used to collect data on demographics, outcomes, and treatment of inpatients who had a C difficile toxin assay performed between January 4, 2009, and April 3, 2009 (period A, preassay change) and between May 21, 2009, and August 17, 2009 (period B, postassay change).

RESULTS

Assays were positive in 240 of 1,221 patients (19.7%) during period A and in 106 of 1160 patients (9.1%) during period B (P < .01). There was no difference in mortality or discharge to hospice between the 2 periods (10.3% vs 10.1%; P = .90). Patients tested in period B were less likely to receive metronidazole or oral vancomycin (P < .01).

CONCLUSIONS

The new EIA resulted in fewer positive tests and reduced anti-CDI therapy. There was no difference in mortality between the 2 periods, suggesting that the decreased incidence was due to increased assay specificity, not decreased sensitivity.

Incidence and clinical features of Clostridium difficile infection in Korea: a nationwide study

The incidence and severity of Clostridium difficile infections (CDI) have increased in Western countries. However, there are limited data regarding the epidemiology of CDI in Eastern countries. This nationwide study was conducted in 17 hospitals to determine temporal trends in CDI incidence (from 2004 to 2008) in South Korea. The total incidence of CDI in Korea was 1·7 cases/1000 adult admissions in 2004, and 2·7/1000 cases in 2008 (P = 0·028). When analysing the clinical features of 1367 CDI patients diagnosed in 2008, oral metronidazole was effective as a first-line treatment for CDI (61·9%). Relapse rate was 8·9% and complicated CDI was only observed in 3·6%. The incidence of CDI increased significantly in Korea from 2004 to 2008. Although the clinical features were milder than in Western countries, the increasing burden of CDI needs ongoing surveillance systems.

Effective utilization of evolving methods for the laboratory diagnosis of Clostridium difficile infection

Physicians should understand the performance characteristics of evolving laboratory tests used to diagnose Clostridium difficile infection if they are to correctly integrate test results with clinical information and formulate an appropriate therapeutic intervention for patients with antibiotic-associated diarrhea.

Evaluation of a loop-mediated isothermal amplification assay for diagnosis of Clostridium difficile infections

A new assay (illumigene C. difficile; Meridian Bioscience), based on the original loop-mediated isothermal amplification (LAMP) assay, was evaluated with 472 unformed stools from patients suspected of Clostridium difficile infection. Compared to the toxigenic culture, the sensitivity, specificity, and positive and negative predictive values were 91.8, 99.1, 91.8, and 99.1% for the illumigene C. difficile assay and 69.4, 100, 100, and 96.6% for the cytotoxicity assay, respectively.

Rapid diagnosis of Clostridium difficile infection by multiplex real-time PCR

The gold standards for the diagnosis of Clostridium difficile infections (CDIs) are the cytotoxicity assay and the toxigenic culture. However, both methods are time-consuming and the results are not available before 24-48 h. We developed and evaluated a multiplex in-house real-time polymerase chain reaction (PCR) assay for the simultaneous detection of toxigenic strains of C. difficile and the presumptive identification of the epidemic NAP1/027/BI strain from stools. Amplifications were performed using specific primers for tcdB and tcdC on an ABI Prism 7300 (Applied Biosystems). The detection of amplicons was done using TaqMan probes. The analytical sensitivity of the multiplex real-time PCR for detecting tcdB was estimated to 10 CFU/g of stools. This assay was assessed from 881 consecutive unformed stools from patients suspected of having CDI. The gold standard was the toxigenic culture for the diagnosis of CDI and PCR ribotyping for the identification of the NAP1/027/BI strain. The prevalence of positive toxigenic culture was 9.31%. Compared to the toxigenic culture, the sensitivity, specificity, and positive and negative predictive values were 86.59%, 97.43%, 78.02%, and 98.57%, respectively, for the real-time PCR and 70.73%, 100%, 100%, and 97.08%, respectively, for the cytotoxicity assay.

Evaluation of four different diagnostic tests to detect Clostridium difficile in piglets

Clostridium difficile is emerging as pathogen in both humans and animals. In 2000 it was described as one of the causes of neonatal enteritis in piglets, and it is now the most common cause of neonatal diarrhea in the United States. In Europe, C. difficile infection (CDI) in both neonatal piglets and adult sows has also been reported. Diagnosis of this infection is based on detection of the bacterium C. difficile or its toxins A and B. Most detection methods, however, are only validated for diagnosing human infections. In this study three commercially available enzyme immunoassays (EIAs) and a commercial real-time-PCR (Becton, Dickinson, and Company) were evaluated by testing 172 pig fecal specimens (139 diarrheic and 33 nondiarrheic piglets). The results of each test were compared to those of cytotoxicity assays (CTAs) and toxigenic culture as the "gold standards." Compared to CTAs, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were, respectively, as follows: for real-time PCR, 91.6, 37.1, 57.6, and 82.5%; for Premier Toxins A&B (Meridian), 83.1, 31.5, 53.1, and 66.7%; for ImmunoCard Toxins A&B kit (ICTAB; Meridian), 86.6, 56.8, 66.9, and 80.7%; and for VIDAS (bioMérieux), 54.8, 92.6, 85.0, and 72.8%. Compared to toxigenic culture, the sensitivity, specificity, PPV, and NPV were, respectively, as follows: for real-time PCR, 93.0, 34.7, 50.0, and 87.5%; for Premier Toxins A&B, 80.3, 27.7, 43.8, and 66.7%; and for ICTAB, 80.0, 46.2, 52.8, and 75.4%; and for VIDAS, 56.4, 89.8, 77.5, and 76.7%. We conclude that all tests had an unacceptably low performance as a single test for the detection of C. difficile in pig herds and that a two-step algorithm is necessary, similar to that in cases of human CDI. Of all of the assays, the real-time PCR had the highest NPV compared to both reference methods and is therefore the most appropriate test to screen for the absence of C. difficile in pigs as a first step in the algorithm. The second step would be a confirmation of the positive results by toxigenic culture.