Evaluation of the chromogenic agar chromID C. difficile

Comparative evaluation of the STANDARD M10 and Xpert C. difficile assays for detection of toxigenic Clostridioides difficile in stool specimens

This study compared the performance of two commercial molecular assays, the STANDARD M10 Clostridioides difficile assay (M10) and the Xpert C. difficile assay (Xpert), for detecting toxigenic C. difficile in stool specimens. A total of 487 consecutive stool specimens submitted for routine C. difficile testing between June and November 2023 were included. Following routine testing using C. DIFF QUIK CHEK COMPLETE (QCC), M10 and Xpert were tested in parallel, alongside toxigenic culture (reference standard). Additionally, two-step algorithms, using QCC on the first step and either M10 or Xpert on the second step, were assessed. Both M10 and Xpert demonstrated a sensitivity and negative predictive value (NPV) of 100%. M10 exhibited significantly higher specificity and positive predictive value (PPV; 91.9% and 64.2%, respectively) than Xpert (90.3% and 59.8%, respectively). Both two-step algorithms showed a sensitivity and NPV of 98.4% and 99.8%, respectively. The specificity and PPV of the two-step algorithm using M10 (95.2% and 75.0%, respectively) were slightly higher than those of the one using Xpert (94.8% and 73.2%, respectively), without statistical significance. Receiver operating characteristic curve analysis, assessing the predictive ability of cycle threshold (Ct) values for the detection of free toxin, exhibited an area under the curve of 0.825 for M10 and 0.843 for Xpert. This indicates the utility of Ct values as predictors for the detection of free toxin in both assays. In conclusion, M10 proves to be an effective diagnostic tool with performance comparable to Xpert, whether utilized independently or as part of a two-step algorithm.

Comparison of commercial assays and two-step approach to detect Clostridioides difficile in South Africa

Background

Clostridioides difficile is the number one cause of hospital-acquired diarrhoea. Accurate diagnosis of C. difficile is of utmost importance as it guides patient management and infection control practices. Studies evaluating the performance of commercially available nucleic acid amplification tests (NAATs) versus algorithms are lacking in resource-limited settings.

Objective

This study assessed the performance of three commercially available tests and a two-step approach for the diagnosis of C. difficile infection using toxigenic culture (TC) as the gold standard.

Methods

Two hundred and twenty-three non-duplicate loose stool samples were submitted to the National Health Laboratory Service Microbiology Laboratory at Tygerberg Hospital, Cape Town, South Africa, from October 2017 to October 2018. The samples were tested in parallel using the C. DIFF QUIK CHEK COMPLETE enzyme immunoassay (EIA) and two NAATs (Xpert C. difficile and BD MAX Cdiff), and the results were compared to TC. The performance of a two-step approach consisting of the C. DIFF QUIK CHEK COMPLETE followed by the Xpert C. difficile was also determined.

Results

Of 223 faecal specimens tested, 37 (16.6%) were TC-positive. The sensitivity and specificity of the C. DIFF QUIK CHEK COMPLETE were 54.1% and 98.9%; Xpert C. difficile, 86.4% and 96.8%; BD MAX Cdiff, 89.2% and 96.8%; and two-step approach, 89.2% and 96.2%.

Conclusion

The C. DIFF QUIK CHEK COMPLETE, in a two-step approach with the Xpert C. difficile, performed similarly to the NAATs on their own and offer advantages in terms of cost and workflow in low-resource settings.

Efficacy of Dry Heat Treatment against Clostridioides difficile Spores and Mycobacterium tuberculosis on Filtering Facepiece Respirators

The COVID-19 pandemic has required novel solutions, including heat disinfection of personal protective equipment (PPE) for potential reuse to ensure availability for healthcare and other frontline workers. Understanding the efficacy of such methods on pathogens other than SARS-CoV-2 that may be present on PPE in healthcare settings is key to worker safety, as some pathogenic bacteria are more heat resistant than SARS-CoV-2. We assessed the efficacy of dry heat treatment against Clostridioides difficile spores and Mycobacterium tuberculosis (M. tb) on filtering facepiece respirator (FFR) coupons in two inoculums. Soil load (mimicking respiratory secretions) and deionized water was used for C. difficile, whereas, soil load and PBS and Tween mixture was used for M. tb. Dry heat treatment at 85 °C for 240 min resulted in a reduction equivalent to 6.0-log10 CFU and 7.3-log10 CFU in C. difficile spores inoculated in soil load and deionized water, respectively. Conversely, treatment at 75 °C for 240 min led to 4.6-log10 CFU reductions in both soil load and deionized water. C. difficile inactivation was higher by >1.5-log10 CFU in deionized water as compared to soil load (p < 0.0001), indicating the latter has a protective effect on bacterial spore inactivation at 85 °C. For M. tb, heat treatment at 75 °C for 90 min and 85 °C for 30 min led to 8-log10 reduction with or without soil load. Heat treatment near the estimated maximal operating temperatures of FFR materials (which would readily eliminate SARS-CoV-2) did not achieve complete inactivation of C. difficile spores but was successful against M. tb. The clinical relevance of surviving C. difficile spores when subjected to heat treatment remains unclear. Given this, any disinfection method of PPE for potential reuse must ensure the discarding of any PPE, potentially contaminated with C. difficile spores, to ensure the safety of healthcare workers.

Comparative Evaluation of Three Immunoassays for the Simultaneous Detection of Clostridioides difficile Glutamate Dehydrogenase and Toxin A/B

Background: In the medical laboratory, a step-by-step workflow for Clostridioides difficile infection (CDI) detection using glutamate dehydrogenase (GDH) and toxin A/B assays for initial screening, along with a nucleic acid amplification test (NAAT), has been recommended recently. In this study, we evaluated these three immunoassays for the simultaneous detection of GDH and Clostridioides difficile (CD) toxin A/B. Methods: A total of 304 stool samples were tested for the presence of GDH antigen and CD toxin A/B using VIDAS C. difficile GDH and toxin A/B (CDAB), RIDASCREEN C. difficile GDH and toxin A/B (RIDA), and C. DIFF QUIK CHEK COMPLETE according to the manufacturers’ recommendations. As complementary reference methods for GDH and toxin A/B detection in the three immunoassays, CD cultures using ChromID C. difficile agar and the Xpert C. difficile assay, respectively, were tested. Results: All three GDH assays showed overall substantial agreement with the CD culture. All three toxin A/B assays showed overall moderate agreement with the Xpert C. difficile assay. In comparison with consensus results, VIDAS GDH and QCC GDH showed almost perfect agreement, whereas RIDA GDH showed inferior but substantial agreement. All three toxin A/B assays showed almost perfect agreement. Conclusions: Since the QCC GDH and toxin A/B assay is relatively more sensitive and specific than the other two immunoassays for discriminating toxigenic or non-toxigenic CDI, QCC is very helpful for the simultaneous identification of GDH and CD toxin A/B in the initial step of the two-round workflow for diagnosing CDI.

High levels of toxigenic Clostridioides difficile contamination of hospital environments: a hidden threat in hospital-acquired infections in Kenya

Introduction

The contribution of Clostridioides difficile (formerly Clostridium difficile) to the burden of hospital-associated infections (HAIs) remains undetermined in many African countries.

Aim

This study aimed to identify a sensitive and readily adaptable C. difficile detection assay and to evaluate the C. difficile HAI risk in Kenya.

Methodology

Sterile swabs in neutralizing buffer were used to sample equipment or surfaces that patients and clinical staff touched frequently. These swabs were either plated directly on chromogenic agar or cultured in an enrichment broth before plating. The swab suspensions, enrichment broth and plate cultures were screened by quantitative PCR (qPCR) to determine the most efficient detection method. The HAI risk was evaluated by testing the C. difficile-positive samples by qPCR for the A, B and binary toxins.

Results

C. difficile was detected on 4/57 (7.0 %) equipment and surfaces by direct culture. The additional enrichment step increased the detection rate 10-fold to 43/57 (75.4 %). In total, 51/57 (89.5 %) environmental samples were positive for C. difficile detected through either culture or qPCR. The genes encoding the primary toxins, tcdA and tcdB, were detected on six surfaces, while the genes encoding the binary toxins, cdtA and cdtB, were detected on 2/57 (3.5 %) and 3/57 (5.3 %) surfaces, respectively. Different C. difficile toxin gene profiles were detected: the tcdA+/tcdB− gene profile on 4/10 (40 %) high-touch surfaces, tcdA−/tcdB+ on 3/10 (30 %) surfaces, tcdA+/tcdB+/cdtA+/cdtB+ on 2/10 (20 %) surfaces and tcdA−/tcdB+/cdtB+ on one high-touch surface.

Conclusion

The widespread contamination of hospital environments by toxigenic C. difficile gives a strong indication of the high risk of C. difficile infections (CDIs). The two-step culture process described can easily be adapted for monitoring hospital environment contamination by C. difficile.

Diagnosis and treatment of Clostridioides difficile infection

Clostridioides difficile is the main cause of healthcare-associated diarrhoea in adults. The incidence of C.difficile infection (CDI) has increased in recent years. The risk of recurrence of CDI is 15%-25% in a first episode and this risk is increased in subsequent episodes. Toxigenic culture and cytotoxicity tests are the reference techniques for the microbiological diagnosis of CDI. These are laborious and slow techniques and therefore they have been replaced in clinical practice by the application of a multi-step algorithm that includes the detection of glutamate dehydrogenase (GDH), toxins and molecular techniques. The treatment of choice for CDI is Vancomycin. In recent years, new drugs and new treatment strategies have appeared that are especially useful in the treatment of relapses of CDI.

Clostridioides difficile: diagnosis and treatments

Clostridioides difficile (formerly Clostridium) is a major cause of healthcare associated diarrhea, and is increasingly present in the community. Historically, C difficile infection was considered easy to diagnose and treat. Over the past two decades, however, diagnostic techniques have changed in line with a greater understanding of the physiopathology of C difficile infection and the use of new therapeutic molecules. The evolution of diagnosis showed there was an important under- and misdiagnosis of C difficile infection, emphasizing the importance of algorithms recommended by European and North American infectious diseases societies to obtain a reliable diagnosis. Previously, metronidazole was considered the reference drug to treat C difficile infection, but more recently vancomycin and other newer drugs are shown to have higher cure rates. Recurrence of infection represents a key parameter in the evaluation of new drugs, and the challenge is to target the right population with the adapted therapeutic molecule. In multiple recurrences, fecal microbiota transplantation is recommended. New approaches, including antibodies, vaccines, and new molecules are already available or in the pipeline, but more data are needed to support the inclusion of these in practice guidelines. This review aims to provide a baseline for clinicians to understand and stratify their choice in the diagnosis and treatment of C difficile infection based on the most recent data available.

Molecular Characterization and Moxifloxacin Susceptibility of Clostridium difficile

In recent years, the incidence and severity of Clostridium difficile infections has increased. Additionally, resistance of C. difficile to frequently used antibiotics is rising. To improve our understanding of C. difficile, there is a need for molecular characterization of different strains and antibiotic resistance testing. We investigated the efficacy of GenoType CDiff kit (Hain Lifesciences) in identification of C. difficile and its various strains in northern Israel. The kit involves a molecular assay that detects C. difficile from stool samples or colonies and identifies the different strains and mutations in the gyrA gene that cause moxifloxacin resistance. Forty-nine C. difficile positive samples were examined by the kit following DNA extraction from both colonies and stool. The identification rate (95.9%) of C. difficile was much higher when DNA was extracted from colonies, compared to extraction from stool (46.9%). Low frequencies of ribotype027 strain (2%) and of ribotype078 strain (4%) were found. There was a high concordance between genotype (mutation in gyrA) and phenotype (Etest) for moxifloxacin resistance (Kappa = 0.72). A high percentage of moxifloxacin-resistant strains was found. Our findings indicate that the GenoType CDiff kit is very effective in characterization of C.difficile strains and less effective for identification of C. difficile directly from stool samples.

Integrated genomic epidemiology and phenotypic profiling of Clostridium difficile across intra-hospital and community populations in Colombia

Clostridium difficile, the causal agent of antibiotic-associated diarrhea, has a complex epidemiology poorly studied in Latin America. We performed a robust genomic and phenotypic profiling of 53 C. difficile clinical isolates established from diarrheal samples from either intrahospital (IH) or community (CO) populations in central Colombia. In vitro tests were conducted to evaluate the cytopathic effect, the minimum inhibitory concentration of ten antimicrobial agents, the sporulation efficiency and the colony forming ability. Eleven different sequence types (STs) were found, the majority present individually in each sample, however in three samples two different STs were isolated. Interestingly, CO patients were infected with STs associated with hypervirulent strains (ST-1 in Clade-2). Three coexistence events (two STs simultaneously detected in the same sample) were observed always involving ST-8 from Clade-1. A total of 2,502 genes were present in 99% of the isolates with 95% of identity or more, it represents a core genome of 28.6% of the 8,735 total genes identified in the set of genomes. A high cytopathic effect was observed for the isolates positive for the two main toxins but negative for binary toxin (TcdA+/TcdB+/CDT- toxin production type), found only in Clade-1. Molecular markers conferring resistance to fluoroquinolones (cdeA and gyrA) and to sulfonamides (folP) were the most frequent in the analyzed genomes. In addition, 15 other markers were found mostly in Clade-2 isolates. These results highlight the regional differences that C. difficile isolates display, being in this case the CO isolates the ones having a greater number of accessory genes and virulence-associated factors.

New Insights into Clostridium difficile (CD) Infection in Latin America: Novel Description of Toxigenic Profiles of Diarrhea-Associated to CD in Bogotá, Colombia

Clostridium difficile (CD) produces antibiotic associated diarrhea and leads to a broad range of diseases. The source of CD infection (CDI) acquisition and toxigenic profile are factors determining the impact of CD. This study aimed at detecting healthcare facility onset- (HCFO) and community-onset (CO) CDI and describing their toxigenic profiles in Bogotá, Colombia. A total of 217 fecal samples from patients suffering diarrhea were simultaneously submitted to two CDI detection strategies: (i) in vitro culture using selective chromogenic medium (SCM; chromID, bioMérieux), followed verification by colony screening (VCS), and (ii) molecular detection targeting constitutive genes, using two conventional PCR tests (conv.PCR) (conv.16S y conv.gdh) and a quantitative test (qPCR.16s). The CD toxigenic profile identified by any molecular test was described using 6 tests independently for describing PaLoc and CdtLoc organization. High overall CDI frequencies were found by both SCM (52.1%) and conv.PCR (45.6% for conv.16S and 42.4% for conv.gdh), compared to reductions of up to half the frequency by VCS (27.2%) or qPCR.16S (22.6%). Infection frequencies were higher for SCM and conv.16S regarding HCFO but greater for CO concerning conv.gdh, such differences being statistically significant. Heterogeneous toxigenic profiles were found, including amplification with lok1/3 primers simultaneously with other PaLoc markers (tcdA, tcdB or tcdC). These findings correspond the first report regarding the differential detection of CDI using in vitro culture and molecular detection tests in Colombia, the circulation of CD having heterogeneous toxigenic profiles and molecular arrays which could affect the impact of CDI epidemiology.

Role of Single Procalcitonin Test on Admission as a Biomarker for Predicting the Severity of Clostridium difficile Infection

Objective: To evaluate whether serum Procalcitonin (PCT) at the early stage of infection can serve as a potential biomarker for determining Clostridium difficile infection (CDI) severity.

Methods: Fifty-four patients diagnosed with CDI were enrolled in the study. Serum samples were obtained within a median time of 24–48 h of the lab result for presence of C. difficile. PCT levels were measured by chemiluminescence immunoassay. Demographic, clinical, and prognostic data concerning the patients were retrospectively collected from medical records. The illness severity score was determined according to “Score indices for C. difficile infection severity.”

Results: We found that serum PCT levels were significantly higher in patients with moderate disease, compared to patients with mild disease (p = 0.0032). Additionally, PCT was correlated with mortality (p = 0.0002), white blood cell count (p = 0.019), and community-acquired disease (p = 0.0345).

Conclusion: Early measurement of PCT may serve as a biomarker for early prediction of CDI severity, which is of great importance due to the high risk of complications and death.

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.

Persistence of Bowl Water Contamination during Sequential Flushes of Contaminated Toilets

Toilets contaminated with infectious organisms are a recognized contact disease transmission hazard. Previous studies indicate that toilet bowl water can remain contaminated for several flushes after the contamination occurs. This study characterized contamination persistence over an extended series of flushes using both indicator particles and viable bacteria. For this study, toilets were seeded with microbe-size microbial surrogates and with Pseudomonas fluorescens or Clostridium difficile bacteria and flushed up to 24 times. Bowl water samples collected after seeding and after each flush indicated the clearance per flush and residual bowl water contaminant concentration. Toilets exhibited 3 + log10 contaminant reductions with the first flush, only 1-2 logs with the second flush, and less than 1 log thereafter. Contamination still was present 24 flushes post contamination. Clearance was modeled accurately by a two-stage exponential decay process. This study shows that toilet bowl water will remain contaminated many flushes after initial contamination, posing a risk of recurring environmental contamination and associated infection incidence.

Antimicrobial susceptibility of Clostridium difficile isolates in Israel

OBJECTIVES

An increase of Clostridium difficile isolates with reduced susceptibility to various antimicrobial agents has been observed, including isolates that are non-susceptible to antibiotics that are routinely used for treatment of C. difficile, such as vancomycin and metronidazole. We determined the susceptibility rates of C. difficile isolates from hospitals in northern Israel to various antibiotics including tigecycline, which was not previously reported from Israel.

METHODS

A total of 81 stool samples were collected from three hospitals in northern Israel from patients with C. difficile infection. Specimens were screened for BI/NAP1/027 ribotype, cultured, and sensitivity tests were performed for vancomycin, metronidazole, moxifloxacin, and tigecycline. Statistical tests were applied for analysing the differences in distribution of resistance between the different antibiotics and between BI/NAP1/027 and resistance of antibiotics.

RESULTS

Reduced susceptibility was found among 6/81 isolates for vancomycin, 4/81 for metronidazole, and 17/81 for moxifloxacin. Only 1 isolate had reduced susceptibility to tigecycline, with a mean MIC of 0.05μg/mL. Reduced susceptibility to moxifloxacin was significantly associated with reduced susceptibility to vancomycin (p=0.016) and to metronidazole (p=0.0276), and reduced susceptibility to metronidazole was associated with reduced susceptibility to vancomycin (p=0.0259). Eight of 81 isolates (9.9%) were positive for BI/NAP1/027 ribotype and had significantly higher non-susceptibility rates to moxifloxacin and vancomycin compared with BI/NAP1/027 negative isolates (p<0.0001 and p=0.0113, respectively).

CONCLUSIONS

We found higher non-susceptibility rates to vancomycin and metronidazole than most previous studies, while tigecycline resistance rates are very low in northern Israel, rendering it a potential agent for treating CDI.

Investigation of community carriage rates of Clostridium difficile and Hungatella hathewayi in healthy volunteers from four regions of England

Faecal samples from 1365 healthy asymptomatic volunteers from four regions in England were screened for the presence of Clostridium difficile between December 2013 and July 2014. The carriage rate of C. difficile in healthy patients was 0.5%, which is lower than reported previously. This study demonstrates that the true community reservoir of C. difficile in the healthy UK population is very low and is, therefore, unlikely to be a reservoir for infections diagnosed in the hospital setting.

C. difficile PCR-ribotype 023 might go undetected when using ChromId C. difficile agar

We compared the performance of the new chromogenic medium ChromID C. difficile with that of CLO agar. ChromID C. difficile agar is a sensitive medium that can accelerate the presumptive identification of C. difficile, however ribotype 023 might go undetected when using this chromogenic medium.

Disparate prevalence of toxigenic and nontoxigenic Clostridium difficile among distinct adult patient populations in a single institution

Clostridium difficile (CD) disease remains a costly and important hospital-associated infection. Although nontoxigenic CD is detected by some CD testing methods, can interfere with some detection algorithms and has been suggested as a treatment for CD disease, little is known about the relative occurrence of toxigenic and nontoxigenic CD in a single institution.We used both chromogenic and selective agar media to recover CD isolates and a molecular method to detect the toxin B gene from over 2400 fresh unformed stool specimens with isolates further tested for the toxin B gene. We recovered 74 nontoxigenic and 306 toxigenic CD isolates for which a collection site could be assigned.The frequency of recovery of toxigenic and nontoxigenic CD for each hospital location and the ratio of toxigenic to nontoxigenic CD were calculated. Although the overall prevalence of toxigenic and nontoxigenic CD was 12.7 % and 3.1 %, respectively, on some wards, 48 % of all CD were nontoxigenic, while on other wards, ≤5 % were nontoxigenic.The disparate ratios of nontoxigenic CD to toxigenic CD presented here for the various 'groups' within the adult veteran population are important to the ongoing discussion and reexamination of other published work on the occurrence of toxigenic and nontoxigenic CD, for evaluating the performance of CD detection tests, for designing infection control strategies and in ultimately understanding both CD carriage and disease.

Performance of the artus C. difficile QS-RGQ Kit for the detection of toxigenic Clostridium difficile

OBJECTIVES

Nucleic acid amplification tests are commonly used for the direct detection of toxigenic Clostridium difficile. We evaluated the diagnostic performance of newly launched, artus C. difficile QS-RGQ Kit (artus C. difficile, QIAGEN, Hilden, Germany), in comparison with toxigenic culture (TC) and Xpert C. difficile (Cepheid, Sunnyvale, CA, USA).

DESIGN AND METHODS

In prospectively collected 261 diarrheal specimens, the artus C. difficile and the Xpert C. difficile assays were performed. TC using chromogenic agar (chromID CD agar, bioMérieux, Marcy-l'Etoile, France) was used a reference method.

RESULTS

Based on TC, the sensitivity and specificity of the artus C. difficile were 98.2% and 93.6%, respectively, and those of the Xpert C. difficile were 94.6% and 94.6%, respectively; there was no statistical difference. The agreement between the artus C. difficile and the Xpert C. difficile was almost perfect (kappa=0.918). In the artus C. difficile, the cycle threshold (Ct) values of tcdA were constantly lower than those of tcdB in all positive specimens (mean Ct, 24.5 vs. 26.4; mean difference of 1.9). Three specimens were considered tcdA+/tcdB- by the difference of Ct cutoffs between tcdA and tcdB (38.3 and 36.5, respectively).

CONCLUSIONS

The performance of the artus C. difficile is excellent compared with TC and is comparable to that of the Xpert C. difficile. Both PCR assays could be useful diagnostic options for the direct detection of toxigenic C. difficile in clinical laboratories. The optimal Ct cutoff of tcdA and tcdB for artus C. difficile may be further validated in following studies.

Correlation between fecal calprotectin levels, disease severity and the hypervirulent ribotype 027 strain in patients with Clostridium difficile infection

Background

Clostridium difficile is the most common infectious etiology of nosocomial diarrhea. Fecal calprotectin (fc) is a sensitive marker of intestinal inflammation, found to be associated with enteric bacterial infections and inflammatory bowel disease.

Methods

We evaluated fc levels using a Chemiluminescent immunoassay method, in hospitalized patients with C. difficile infection (CDI) diagnosed by molecular stool examination and assessed correlation with virulent ribotype 027 strain infection, antibiotic susceptibility by gradient Etest strip performed on C. difficile colonies and clinical and laboratory measures of disease severity. Statistical analysis was performed for correlation of fc levels with clinical and laboratory parameters, disease severity and patient outcomes.

Results

Overall 29 patients with CDI were admitted at the Poria medical center in northern Israel, during June 2014-May 2015. Resistance to metronidazole was found in 3 (10.3 %) isolates and to vancomycin in 5 (17.2 %) isolates. Regarding patient outcomes, within 30 days of CDI diagnosis, recurrence of disease occurred in 10 (34.5 %) patients and 2 patients (6.9 %) died. Seven (24.1 %) isolates were C. difficile ribotype 027. Mean fc level was 331.4 μg/g (21–932). Higher fc levels were found in patients with C. difficile ribotype 027 (p < 0.0005). Fc levels were also correlated with elevated peripheral blood white cell count (p = 0.0007). A trend for higher fc levels was found in patients with a higher clostridium severity score index (p = 0.0633). No correlation was found between fecal calprotectin levels and age, sex, functional status, community versus hospital acquired CDI, antibiotic susceptibility, fever, and creatinine levels.

Conclusions

Our study highlights the fact that fc has a potential role as a biomarker of disease severity and binary toxin producing ribotype associated disease.

Determination of the extent of Clostridium difficile colonisation and toxin accumulation in sows and neonatal piglets

Clostridium difficile is an important spore-forming, opportunistic pathogen in animal husbandry and health care. In pig farming, only neonatal piglets are affected, and diarrhoea and necrotising lesions are common symptoms leading to dehydration and in some cases death. This study aimed at the assessment of the quantitative development of C. difficile colonisation in neonatal piglets by determining the shedding of spores and C. difficile toxins A (TcdA) and B (TcdB) concentrations in sow (n = 5-6) and piglet pen faeces (n = 5-6) at different time points. Spores were quantified on selective agar plates and toxins using ELISA method. C. difficile was not detected in the faeces of all but one sow during the perinatal period. Faeces of 2- and 4-day-old piglets contained 0.65 log cells/g and 5.88 log cells/g of C. difficile, respectively. Toxins were detected on day 4 at a concentration of 2.13 log ng/g (TcdA) and 2.06 log ng/g (TcdB). On day 6, concentration of C. difficile reached 6.14 log CFU/g and toxins 2.02 log ng/g (TcdA) and 2.20 log ng/g (TcdB). Two-week-old piglets showed 4.72 log CFU/g of C. difficile but toxins could not be detected. At 21 days of age, both C. difficile and toxins were undetectable. The concentration and the prevalence of C. difficile were positively associated with the prevalence of toxins in piglets. A very short time window for colonisation by C. difficile, including toxin-producing strains can be observed in neonatal piglets. The significance for animal health and the risk of a carrier status need to be addressed in future studies.

Susceptibility and molecular characterization of Candida species from patients with vulvovaginitis

Vulvovaginal candidiasis affects women of reproductive age, which represents approximately 15–25% of vaginitis cases. The present study aimed to isolate and characterize yeast from the patients irrespective of the presentation of clinical symptoms. The isolates were subjected to in vitro susceptibility profile and characterization by molecular markers, which intended to assess the distribution of species. A total of 40 isolates were obtained and identified through the CHROMagar, API20aux and by ITS and D1/D2 regions sequencing of DNAr gene. Candida albicans strains were genotyped by the ABC system and the isolates were divided into two genotypic groups. The identity of the C. albicans, C. glabrata, C. guilliermondii, C. kefyr and Saccharomyces cerevisiae isolates was confirmed by the multilocus analysis. The strains of Candida, isolated from patients with complications, were found to be resistant to nystatin but sensitive to fluconazole, amphotericin B and ketoconazole, as observed by in vitro sensitivity profile. The isolates from asymptomatic patients, i.e., the colonized group, showed a dose-dependent sensitivity to the anti-fungal agents, fluconazole and amphotericin B. However, the isolates of C. albicans that belong to distinct genotypic groups showed the same in vitro susceptibility profile.

The importance of matrix-assisted laser desorption ionization-time of flight mass spectrometry for correct identification of Clostridium difficile isolated from chromID C. difficile chromogenic agar

The clinical workflow of using chromogenic agar and matrix-assisted laser desorption ionization time-of-fight mass spectrometry (MALDI-TOF MS) for Clostridium difficile identification was evaluated. The addition of MALDI-TOF MS identification after the chromID C. difficile chromogenic agar culture could significantly improve the diagnostic accuracy of C. difficile.

Clostridium difficile infections among adults and children in Mwanza/Tanzania: is it an underappreciated pathogen among immunocompromised patients in sub-Saharan Africa?

Little is known regarding the epidemiology Clostridium difficile in developing countries. Fresh stool samples from patients with diarrhoea were cultured anaerobically. C. difficile was detected in nine (6.4%) of 141 (95% confidence interval 4.2–13.1), of which seven (77.8%) were from children. HIV infection, prolonged hospitalization and antibiotic use were independent factors associated with the occurrence of C. difficile in the gastrointestinal tract. Two of the toxigenic isolates were typed as ribotype 045, and the other two had unknown ribotype. All C. difficile isolates were susceptible to metronidazole, moxifloxacin and clarithromycin, while three isolates were resistant to clarithromycin. C. difficile may be an important pathogen causing diarrhoea in sub-Saharan Africa among immunocompromised patients.

Isolation and Identification of Clostridium difficile Using ChromID C. difficile Medium Combined With Gram Staining and PRO Disc Testing: A Proposal for a Simple Culture Process

Background

ChromID C. difficile agar (CDIF; bioMérieux, France), a chromogenic medium, allows for the isolation and identification of Clostridium difficile strains within 24 hr regardless of pretreatment of stool specimens with heat or alcohol shock. In the present study, we designed and evaluated a simple procedure for the implementation C. difficile cultures using CDIF medium in a tertiary hospital setting.

Methods

We designed a simple protocol for untreated stool specimens using CDIF medium followed by Gram staining and PRO disc (PRO disc K1532B, Key Scientific Products, USA) testing for the identification of C. difficile in colonies produced on CDIF agar. A total of 1,402 prospectively collected stool specimens from patients with suspected C. difficile infection were tested. The protocol was evaluated by phenotypic or molecular identification of C. difficile using Vitek 2 ANC card (bioMérieux) or 16S rDNA/tpi gene sequencing, respectively.

Results

Of 1,402 stool specimens, 650 isolates were cultured in CDIF. Overall, 235 (36.2%, 235/650) strains could be presumptively identified as C. difficile by using Gram staining and PRO disc testing. Of those, 231 (98.3%, 231/235) isolates were confirmed as true C. difficile by molecular assays.

Conclusions

The use of CDIF combined with Gram staining and PRO disc testing of untreated stool specimens would allow for isolation and accurate identification of C. difficile strains and would be advantageous in reducing the multistep process for C. difficile culture.

Evaluation of 3 automated real-time PCR (Xpert C. difficile assay, BD MAX Cdiff, and IMDx C. difficile for Abbott m2000 assay) for detecting Clostridium difficile toxin gene compared to toxigenic culture in stool specimens

We evaluated the performance of the 3 automated systems (Cepheid Xpert, BD MAX, and IMDx C. difficile for Abbott m2000) detecting Clostridium difficile toxin gene compared to toxigenic culture. Of the 254 stool specimens tested, 87 (48 slight, 35 moderate, and 4 heavy growth) were toxigenic culture positive. The overall sensitivities and specificities were 82.8% and 98.8% for Xpert, 81.6% and 95.8% for BD MAX, and 62.1% and 99.4% for IMDx, respectively. The specificity was significantly higher in IMDx than BD MAX (P= 0.03). All stool samples underwent toxin A/B enzyme immunoassay testing, and of the 254 samples, only 29 samples were positive and 2 of them were toxigenic culture negative. Considering the rapidity and high specificity of the real-time PCR assays compared to the toxigenic culture, they can be used as the first test method for C. difficile infection/colonization.

Nationwide surveillance study of Clostridium difficile in Australian neonatal pigs shows high prevalence and heterogeneity of PCR ribotypes

Clostridium difficile is an important enteric pathogen of humans and the cause of diarrhea and enteritis in neonatal pigs. Outside Australia, prevalence in piglets can be up to 73%, with a single PCR ribotype (RT), 078, predominating. We investigated the prevalence and genotype of C. difficile in Australian pig herds. Rectal swabs (n = 229) were collected from piglets aged <7 days from 21 farms across Australia. Selective culture for C. difficile was performed and isolates characterized by PCR for toxin genes and PCR ribotyping. C. difficile was isolated from 52% of samples by direct culture on chromogenic agar and 67% by enrichment culture (P = 0.001). No association between C. difficile recovery or genotype and diarrheic status of either farm or piglets was found. The majority (87%; 130/154) of isolates were toxigenic. Typing revealed 23 different RTs, several of which are known to cause disease in humans, including RT014, which was isolated most commonly (23%; 36/154). RT078 was not detected. This study shows that colonization of Australian neonatal piglets with C. difficile is widespread in the herds sampled.

Evaluation of the illumigene C. difficile assay for toxigenic Clostridium difficile detection: a prospective study of 302 consecutive clinical fecal samples

Toxigenic Clostridium difficile is a major pathogen causing nosocomial diarrhea. Consequently, rapid detection of toxigenic C. difficile is very important in clinical laboratories. The illumigene C. difficile DNA amplification assay (illumigene; Meridian Bioscience, Inc.) is a rapid method that detects the toxin A gene (tcdA) by loop-mediated isothermal amplification. In the present study, we evaluated the diagnostic performance of the illumigene assay using 302 consecutive stool specimens in comparison with the VIDAS C. difficile A&B enzyme-linked fluorescent immunoassay (VIDAS-CDAB; bioMérieux). Toxigenic culture was used as the reference method. The sensitivity, specificity, positive predictive value, and negative predictive value of the illumigene assay were 88.1%, 96.7%, 86.7%, and 97.1%, respectively, while those of the VIDAS-CDAB assay were 40.4%, 98.8%, 87.5%, and 88.5%, respectively. It is of note that use of a combination of the illumigene and VIDAS-CDAB assays did not improve any of the 4 evaluated parameters (88.1%, 95.5%, 82.5%, and 97.1%, respectively). The illumigene assay showed limits of detection of 250 and 11,467 CFU/mL for ATCC 9688 (tcdA+, tcdB+, cdtB-) and ATCC 43598 (tcdA-, tcdB+, cdtB-) reference strains, respectively, and there was no cross-reactivity with 8 frequently isolated bacterial species. In conclusion, the illumigene assay might be a useful method for rapid detection of toxigenic C. difficile in clinical laboratories. Additionally, the VIDAS-CDAB assay seems unnecessary if the illumigene assay is used.

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.

Laboratory detection of Clostridium difficile in piglets in Australia

Clostridium difficile is a well-known enteric pathogen of humans and the causative agent of high-morbidity enteritis in piglets aged 1 to 7 days. C. difficile prevalence in Australian piglets is as high as 70%. The current diagnostic assays have been validated only for human infections, and there are no published studies assessing their performance in Australian piglets. We evaluated the suitability of five assays for detecting C. difficile in 157 specimens of piglet feces. The assays included a loop-mediated isothermal amplification (LMIA)-PCR for tcdA (illumigene C. difficile; Meridian), a real-time PCR for tcdB (GeneOhm Cdiff; Becton Dickinson), two-component enzyme immunoassays (EIA) for C. difficile glutamate dehydrogenase (GDH) (EIA-GDH) and TcdA/TcdB (EIA-TcdA/TcdB) (C. diff Quik Chek; Alere), and direct culture (DC) (C. difficile chromID agar; bioMérieux). The assays for detection of the organism were compared against enrichment culture (EC), and assays for detection of toxins/toxin genes were compared against EC followed by PCR for toxin genes (toxigenic EC [TEC]). The recovery of C. difficile by EC was 39.5% (n = 62/157), and TEC revealed that 58.1% (n = 36/62) of isolates were positive for at least one toxin gene (tcdA/tcdB). Compared with those for EC/TEC, the sensitivities, specificities, positive predictive values, and negative predictive values were, respectively, as follows: DC, 91.9, 100.0, 100.0, and 95.0%; EIA-GDH, 41.9, 92.6, 78.8, and 71.0%; EIA-TcdA/TcdB, 5.6, 99.2, 66.7, and 77.9%; real-time PCR, 42.9, 96.7, 78.9, and 85.4% and LMIA-PCR, 25.0, 95.9, 64.3, and 81.1%. The performance of the molecular methods was poor, suggesting that the current commercially available assays for diagnosis of C. difficile in humans are not suitable for use in piglets. C. difficile recovery by the DC provides a cost-effective alternative.

Comparison of culture based methods for the isolation of Clostridium difficile from stool samples in a research setting

Effective isolation of Clostridium difficile from stool samples is important in the research setting, especially where low numbers of spores/vegetative cells may be present within a sample. In this study, three protocols for stool culture were investigated to find a sensitive, cost effective and timely method of C. difficile isolation. For the initial enrichment step, the effectiveness of two different rich media, cycloserine-cefoxitin fructose broth (CCFB) and cycloserine-cefoxitin mannitol broth with taurocholate and lysozyme (CCMB-TAL) were compared. For the comparison of four different, selective solid media; Cycloserine-cefoxitin fructose agar (CCFA), Cycloserine-cefoxitin egg yolk agar (CCEY), ChromID C. difficile and tryptone soy agar (TSA) with 5% sheep's blood with and without preceding broth enrichment were used. As a means to enable differentiation between C. difficile and other fecal flora, the effectiveness of the inclusion of a pH indictor (1% Neutral Red), was also evaluated. The data derived indicated that CCFB is more sensitive than CCMB-TAL, however, the latter had an improved recovery rate. A broth enrichment step had a reduced sensitivity over direct plating. ChromID C. difficile showed the best recovery rate whereas CCEY egg yolk agar was the most sensitive of the four. The addition of 1% Neutral Red did not show sufficient colour change when added to CCEY egg yolk agar to be used as a differential medium. For a low cost, timely and sensitive method of isolating C. difficile from stool samples we recommend direct plating onto CCEY egg yolk agar after heat shock.

Evaluation of a chromogenic culture medium for the detection of Clostridium difficile

PURPOSE

Clostridium difficile (C. difficile) is an important cause of nosocomial diarrhea. Diagnostic methods for detection of C. difficile infection (CDI) are shifting to molecular techniques, which are faster and more sensitive than conventional methods. Although recent advances in these methods have been made in terms of their cost-benefit, ease of use, and turnaround time, anaerobic culture remains an important method for detection of CDI.

MATERIALS AND METHODS

In efforts to evaluate a novel chromogenic medium for the detection of C. difficile (chromID CD agar), 289 fecal specimens were analyzed using two other culture media of blood agar and cycloserine-cefoxitin-fructose-egg yolk agar while enzyme immunosorbent assay and polymerase chain reaction-based assay were used for toxin detection.

RESULTS

ChromID showed the highest detection rate among the three culture media. Both positive rate and sensitivity were higher from chromID than other culture media. ChromID was better at detecting toxin producing C. difficile at 24 h and showed the highest detection rate at both 24 h and 48 h.

CONCLUSION

Simultaneous use of toxin assay and anaerobic culture has been considered as the most accurate and sensitive diagnostic approach of CDI. Utilization of a more rapid and sensitive chromogenic medium will aid in the dianogsis of CDI.

Diagnosis of Clostridium difficile infection: the molecular approach

Diagnosis of Clostridium difficile infection is based on clinical presentation and laboratory tests. Although numerous laboratory methods are now available, the diagnosis of C. difficile infection remains challenging. Nucleic acid amplification tests (NAATs) are the most recent marketed methods. These methods detect genes for toxins A and/or B. They are very sensitive compared with the reference method (toxigenic culture) and are thus very promising, despite their cost. However, a positive NAAT result must be interpreted with caution owing to the possible detection of asymptomatic carriers of toxigenic strains who may have diarrhea for other reasons. The place of NAATs in current diagnostic strategies needs to be better defined, but the rapidity of the result is interesting for early recognition of the disease.

Comparison of the Verigene Clostridium difficile, Simplexa C. difficile Universal Direct, BD MAX Cdiff, and Xpert C. difficile assays for the detection of toxigenic C. difficile

We compared the Verigene Clostridium difficile test (Nanosphere, Northbrook, IL, USA), the Simplexa C. difficile Universal Direct (Focus Diagnostics, Cypress, CA, USA), the BD MAX Cdiff (Becton Dickinson, Franklin Lakes, NJ, USA), and the Xpert C. difficile (Cepheid, Sunnyvale, CA, USA) assays for the detection of toxigenic C. difficile. One hundred and ninety deidentified, remnant diarrheal specimens were included in this study. After resolution of discordant results by toxigenic culture, the Xpert C. difficile assay displayed the highest sensitivity (100%), with a specificity of 98.8%. The sensitivity and specificity were 95.2% and 99.4% and 87% and 100% for the Verigene CDF and Simplexa Universal Direct assays, respectively. Finally, the BD MAX assay showed a sensitivity of 87% and a specificity of 98.8%. Despite differences in the overall performance of these assays, these results support the routine use of these platforms for the detection of toxigenic C. difficile in the clinical laboratory.

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.

Development of a novel method for detection of Clostridium difficile using HS-SPME-GC-MS

AIMS

A novel method has been developed that allows successful differentiation between Clostridium difficile culture-positive and culture-negative stool samples based on volatile organic compound (VOC) evolution and detection by headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS).

METHODS AND RESULTS

The method is based on the activation of p-hydroxyphenylacetate decarboxylase produced by Cl. difficile and the detection of a specific VOC, that is 2-fluoro-4-methylphenol from an enzyme substrate. In addition, other VOCs were good indicators for Cl. difficile, that is isocaproic acid and p-cresol, although they could not be used alone for identification purposes. One hundred stool samples were tested, of which 77 were positive by culture. Detection using HS-SPME-GC-MS allowed confirmation of the presence of Cl. difficile within 18 h with a sensitivity and specificity of 83·1 and 100%, respectively.

CONCLUSIONS

It is recommended that this new approach could be used alongside conventional methods for Cl. difficile detection, including toxin detection methods, which would allow any false-negative results to be eliminated.

SIGNIFICANCE AND IMPACT OF THE STUDY

The ability to identify Cl. difficile-positive stool samples by the analysis of VOCs could allow the development of a VOC detection device which could allow rapid diagnosis of disease and hence prompt treatment with appropriate antibiotics.

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.

Isolation of Clostridium difficile from faecal specimens--a comparison of chromID C. difficile agar and cycloserine-cefoxitin-fructose agar

The culture of toxigenic Clostridium difficile from stool specimens is still seen as the gold standard for the laboratory diagnosis of C. difficile infection (CDI). bioMérieux have released ChromID Cdiff chromogenic agar (CDIF) for the isolation and identification of C. difficile in 24 h. In this study, we compared CDIF to pre-reduced cycloserine-cefoxitin-fructose agar with sodium taurocholate (TCCFA) in the examination of glutamate dehydrogenase-positive faecal specimens that were either GeneOhm positive or negative, using direct culture or culture following alcohol shock. Direct culture on CDIF had a sensitivity of 100 % and recovery of 94 % while for TCCFA these were 87 % and 82 %, respectively. For GeneOhm-positive alcohol-shocked faecal samples, sensitivity and recovery on CDIF was similar to direct culture while on TCCFA they were about 10 % higher. For direct culture, there was a significant difference between growth on CDIF at 24 h and TCCFA at 48 h (P = 0.001) and between the two media at 48 h (P<0.001). A total of 142 strains of C. difficile were recovered in pure culture from all GeneOhm-positive samples used in this study and 11 (7.7 %) of these were A(-)B(-)CDT(-) and may represent mixed infections of toxigenic and non-toxigenic C. difficile. The most dominant ribotype was UK 014 (14.7 %) followed by 002 (11.9 %) and 020 (11.9 %), and 36 % of toxigenic isolates, including an A(-)B(+)CDT(-) strain, could not be assigned a UK ribotype. CDIF outperformed pre-reduced TCCFA by negating the need for alcohol shock treatment and by giving a time saving of 24 h in the isolation of C. difficile. CDIF plates were also more selective than TCCFA and C. difficile colonies were easy to identify and subculture prior to strain typing.

Evaluation of the fully automated BD MAX Cdiff and Xpert C. difficile assays for direct detection of Clostridium difficile in stool specimens

We evaluated the fully automated molecular BD MAX Cdiff assay (BD Diagnostics) and the Xpert C. difficile test (Cepheid) for rapid detection of Clostridium difficile infection. Culture was done on chromogenic agar followed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry identification and toxin detection. Repeat testing was required for 1.8% and 6.0% of the BD MAX and Xpert tests, respectively. Sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) were 90.5%, 97.9%, 89.3%, and 98.1%, respectively, for BD MAX and 97.3%, 97.9%, 90.0%, and 99.5%, respectively, for Xpert.