BACKGROUND: Antimicrobial susceptibility testing (AST) of Clostridium difficile is increasingly important because of the rise in resistant strains. The standard medium for the AST of C. difficile is supplemented Brucella agar (sBA), but we found that the growth of C. difficile on sBA was not optimal. Because active growth is critical for reliable AST, we developed a new, modified C. difficile (mCD) agar. C. difficile grew better on mCD agar than on sBA. METHODS: C. difficile isolates were collected from patients with healthcare-associated diarrhea. sBA medium was prepared according to the CLSI guidelines. Homemade mCD agar containing taurocholate, L-cysteine hydrochloride, and 7% horse blood was used. For 171 C. difficile isolates, we compared the agar dilution AST results from mCD agar with those from sBA. RESULTS: No significant differences were observed in the 50% minimal inhibitory concentration (MIC50) and 90% minimal inhibitory concentration (MIC90) of clindamycin (CLI), metronidazole (MTZ), moxifloxacin (MXF), piperacillin-tazobactam (PTZ), and rifaximin (RIX), but the values for vancomycin (VAN) were two-fold higher on mCD agar than on sBA. The MICs of CLI, MXF, and RIX were in 100% agreement within two-fold dilutions, but for MTZ, VAN, and PTZ, 13.7%, 0.6%, and 3.1% of the isolates, respectively, were outside the acceptable range. CONCLUSIONS: The MIC ranges, MIC50 and MIC90, were acceptable when AST was performed on mCD agar. Thus, mCD agar could be used as a substitute medium for the AST of C. difficile.
Anti-Infective Agents/*pharmacology ; Clostridium Infections/microbiology ; Clostridium difficile/*drug effects/isolation & purification ; Diarrhea/*microbiology ; Humans ; Microbial Sensitivity Tests/*methods

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.
Chromogenic Compounds/chemistry ; Clostridium difficile/chemistry/*isolation & purification ; Culture Media/*chemistry

Clostridioides ; Clostridioides difficile/isolation & purification* ; Clostridium Infections/epidemiology* ; Guidelines as Topic ; Humans

Infection with Clostridium difficile is a growing concern because of the increasing prevalence and spread of nosocomial infections. Emergence of the hypervirulent 027/NAP1/BI strain is also notable. Existing diagnostic methods have low sensitivity or are time-consuming. Therefore, establishing a rapid and accurate microbiological diagnostic assay is needed. We evaluated the Xpert C. difficile assay (Xpert CD assay; Cepheid, USA) to detect toxigenic C. difficile. This assay is a real-time multiplex PCR assay that can be used to detect toxigenic C. difficile strains and differentiate the C. difficile presumptive 027/NAP1/BI strain. A total of 253 loose stool specimens were collected and toxigenic cultures, VIDAS C. difficile A & B assays (VIDAS CDAB assay; bioMerieux, France), and the Xpert CD assay were performed. In comparison to toxigenic cultures, the sensitivity, specificity, and positive and negative predictive values were 100%, 94.6%, 83.1%, and 100%, respectively, for the Xpert CD assay and 40.8%, 98.0%, 100%, and 88.9%, respectively, for VIDAS CDAB assay. Because of the low prevalence of the PCR ribotype 027 in Korea, the evaluation of the usefulness of the Xpert CD assay for screening for the 027 strain was limited. The Xpert CD assay provides great sensitivity in diagnosing toxigenic C. difficile infection. In addition, this method has excellent usability because it is simple and fast.
Clostridium Infections/*diagnosis/epidemiology/microbiology ; Clostridium difficile/genetics/*isolation & purification/metabolism ; Face/microbiology ; Humans ; Multiplex Polymerase Chain Reaction ; Prevalence ; Reagent Kits, Diagnostic/*standards ; Sensitivity and Specificity

BACKGROUND: Clostridium difficile is a major cause of antibiotic-associated diarrhea. The objective of this study was to characterize clinical isolates of C. difficile obtained from various regions in Korea with regard to their toxin status, molecular type, and antimicrobial susceptibility. METHODS: We analyzed a total of 408 C. difficile isolates obtained between 2006 and 2008 from 408 patients with diarrhea in 12 South Korean teaching hospitals. C. difficile toxin genes tcdA, tcdB, cdtA, and cdtB were detected by PCR. Molecular genotyping was performed by PCR ribotyping. Antimicrobial susceptibilities of the 120 C. difficile isolates were assessed by agar dilution methods. RESULTS: Among 337 toxigenic isolates, 105 were toxin A-negative and toxin B-positive (A-B+) and 29 were binary toxin-producing strains. PCR ribotyping showed 50 different ribotype patterns. The 5 most frequently occurring ribotypes comprised 62.0% of all identified ribotypes. No isolate was susceptible to cefoxitin, and all except 1 were susceptible to piperacillin and piperacillin-tazobactam. The resistance rates of isolates to imipenem, cefotetan, moxifloxacin, ampicillin, and clindamycin were 25%, 34%, 42%, 51%, and 60%, respectively. The isolates showed no resistance to metronidazole or vancomycin. CONCLUSIONS: This is the first nationwide study on the toxin status, including PCR ribotyping and antimicrobial resistance, of C. difficile isolates in Korea. The prevalence of A-B+ strains was 25.7%, much higher than that reported from other countries. Binary toxin-producing strains accounted for 7.1% of all strains, which was not rare in Korea. The most prevalent ribotype was ribotype 017, and all A-B+ strains showed this pattern. We did not isolate strains with decreased susceptibility to metronidazole or vancomycin.
Clostridium Infections/microbiology ; Clostridium difficile/classification/*genetics/isolation & purification ; Diarrhea/microbiology ; *Drug Resistance, Bacterial ; Enterotoxins/*genetics ; Genetic Variation ; Genotype ; Hospitals, University ; Humans ; Microbial Sensitivity Tests ; Republic of Korea ; Ribotyping

OBJECTIVETo develop a real-time PCR assay for the rapid identification of Clostridium(C.)difficile and its toxin.

METHODSTaqMan real-time PCR was developed for the rapid identification of species specific gene(tpi) of C. difficile strains and the toxins A(TcdA), B(TcdB) and truncated toxin A(TcdAT). Sensitivity, specificity and anti-interference ability of these methods were estimated, as well. Feces sampled from fifty diarrhea patients were tested by real-time PCR and compared to the results from VIDAS assay.

RESULTSThe detection limits of tpi were 6×10⁻² CFU/µl and 6 × 10⁻¹ CFU/µl in the non-oxin producing and toxin producing strains, respectively. The coefficients of variability(CV) of intra-assay and inter-assay for the detection limits of tpi in the non-toxin producing strain were 2.1% and 2.3% . The CVs of intra-assay and inter-assay for the detection limit of tpi, tcdA, tcdB and tcdAT in the toxin producing strain were 3.0% and 3.4%, 2.9% and 3.2%, 5.3% and 5.7%, 2.7% and 2.8%, respectively. No interference was detected from other genus or species in clostridium. From 50 clinical samples, thirty-nine of them were negative and six of them were positive under the TaqMan-MGB probe technique in accordance with VIDAS. Five samples appeared positive using the TaqMan-MGB probe technique, in which 3 were dubious and 2 were negative under VIDAS.

CONCLUSIONThe newly developed method was a sensitive and reliable assay for rapid identification of C. difficile and its toxin. This method could be used to screen C. difficile isolates harboring truncated toxin A to avoid misdiagnosis, clinically.

Bacterial Proteins ; isolation & purification ; Bacterial Toxins ; isolation & purification ; Clostridium difficile ; isolation & purification ; Enterotoxins ; isolation & purification ; Real-Time Polymerase Chain Reaction ; methods

BACKGROUND: We evaluated the performance of four commercial nucleic acid amplification tests (NAATs: Xpert C. difficile, BD MAX Cdiff, IMDx C. difficile for Abbott m2000, and Illumigene C. difficile) for direct and rapid detection of Clostridium difficile toxin genes. METHODS: We compared four NAATs on the same set of 339 stool specimens (303 prospective and 36 retrospective specimens) with toxigenic culture (TC). RESULTS: Concordance rate among four NAATs was 90.3% (306/339). Based on TC results, the sensitivity and specificity were 90.0% and 92.9% for Xpert; 86.3% and 89.3% for Max; 84.3% and 94.4% for IMDx; and 82.4% and 93.7% for Illumigene, respectively. For 306 concordant cases, there were 11 TC-negative/NAATs co-positive cases and 6 TC-positive/NAATs co-negative cases. Among 33 discordant cases, 18 were only single positive in each NAAT (Xpert, 1; Max, 12; IMDx, 1; Illumigene, 4). Positivity rates of the four NAATs were associated with those of semi-quantitative cultures, which were maximized in grade 3 (>100 colony-forming unit [CFU]) compared with grade 1 (<10 CFU). CONCLUSIONS: Commercial NAATs may be rapid and reliable methods for direct detection of tcdA and/or tcdB in stool specimens compared with TC. Some differences in the sensitivity of the NAATs may partly depend on the number of toxigenic C. difficile in stool specimens.
Bacterial Proteins/genetics ; Bacterial Toxins/genetics ; Clostridium Infections/*diagnosis/microbiology ; Clostridium difficile/*genetics/isolation & purification ; DNA, Bacterial/*analysis/metabolism ; Enterotoxins/genetics ; Feces/*microbiology ; Humans ; *Multiplex Polymerase Chain Reaction ; Reagent Kits, Diagnostic ; Sensitivity and Specificity

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

BACKGROUND/AIMS: The direct toxic effects of antibiotics on the intestine can alter digestive functions and cause pathogenic bacterial overgrowth leading to antibiotic-associated diarrhea (AAD). Clostridium difficile (C. difficile) is widely known to be responsible for 10~20% of AAD cases. However, Klebsiella oxytoca, Clostridium perfringens, Staphylococcus aureus, and Candida species might also contribute to AAD. METHODS: We prospectively analyzed the organisms in stool and colon tissue cultures with a C. difficile toxin A assay in patients with AAD between May and December 2005. In addition, we performed the C. difficile toxin A assays using an enzyme-linked fluorescent assay technique. Patients were enrolled who had diarrhea with more than three stools per day for at least 2 days after the initiation of antibiotic treatment for up to 6~8 weeks after antibiotic discontinuation. RESULTS: Among 38 patients (mean age 59+/-18 years, M:F=18:20), the organism isolation rates were 28.9% (11/38) for stool culture, 18.4% (7/38) for colon tissue cultures and 13.2% (5/38) for the C. difficile toxin A assay. The overall rate of identification of organisms was 50.0% (19/38). Of the five patients that had a positive result by the C. difficile toxin A assay, two had no organism isolated by the stool or colon tissue culture. The organisms isolated from the stool cultures were C. difficile (4), Klebsiella pneumoniae (K. pneumoniae) (3), Candida species (3), and Staphylococcus aureus (1). C. difficile (4) and K. pneumoniae (3) were isolated from the colon tissue culture. CONCLUSIONS: For C. difficile negative AAD patients, K. pneumoniae, Candida species, and Staphylococcus aureus were found to be potential causative organisms.
Adult ; Aged ; Aged, 80 and over ; Anti-Bacterial Agents/*adverse effects ; Candida/isolation & purification ; Clostridium difficile/isolation & purification ; Diarrhea/diagnosis/*etiology/microbiology ; Endoscopy, Gastrointestinal ; Female ; Humans ; Klebsiella pneumoniae/isolation & purification ; Male ; Middle Aged ; Prospective Studies ; Staphylococcus aureus/isolation & purification

BACKGROUND: The aim of this study was to develop and validate a multiplex real-time PCR assay for simultaneous identification and toxigenic type characterization of Clostridium difficile. METHODS: The multiplex real-time PCR assay targeted and simultaneously detected triose phosphate isomerase (tpi) and binary toxin (cdtA) genes, and toxin A (tcdA) and B (tcdB) genes in the first and sec tubes, respectively. The results of multiplex real-time PCR were compared to those of the BD GeneOhm Cdiff assay, targeting the tcdB gene alone. The toxigenic culture was used as the reference, where toxin genes were detected by multiplex real-time PCR. RESULTS: A total of 351 stool samples from consecutive patients were included in the study. Fifty-five stool samples (15.6%) were determined to be positive for the presence of C. difficile by using multiplex real-time PCR. Of these, 48 (87.2%) were toxigenic (46 tcdA and tcdB-positive, two positive for only tcdB) and 11 (22.9%) were cdtA-positive. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) of the multiplex real-time PCR compared with the toxigenic culture were 95.6%, 98.6%, 91.6%, and 99.3%, respectively. The analytical sensitivity of the multiplex real-time PCR assay was determined to be 103colonyforming unit (CFU)/g spiked stool sample and 0.0625 pg genomic DNA from culture. Analytical specificity determined by using 15 enteric and non-clostridial reference strains was 100%. CONCLUSIONS: The multiplex real-time PCR assay accurately detected C. difficile isolates from diarrheal stool samples and characterized its toxin genes in a single PCR run.
ADP Ribose Transferases/genetics ; Bacterial Proteins/*genetics ; Bacterial Toxins/*genetics ; Clostridium difficile/isolation & purification/*metabolism ; DNA, Bacterial/genetics/metabolism ; Enterotoxins/genetics ; Feces/*microbiology ; Humans ; Multiplex Polymerase Chain Reaction ; Prospective Studies ; Real-Time Polymerase Chain Reaction ; Triose-Phosphate Isomerase/genetics