New types of toxin A-negative, toxin B-positive strains among clinical isolates of Clostridium difficile in Australia

Elliott, Briony; Squire, Michelle M; Thean, Sara; Chang, Barbara J.; Brazier, Jon S.; Rupnik, Maja; Riley, Thomas V.

doi:10.1099/jmm.0.031062-0

Cited by 55 publications

(41 citation statements)

References 33 publications

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“…Toxinotypes XXIII and XXIV were briefly described as new types (24), and types XXV to XXIX and types XXXIII and XXXIV were not included in any previous publication and are described here for the first time. Two new A Ϫ B ϩ toxinotypes from Australia, XXX and XXXI, have been reported (25), while another A Ϫ B ϩ toxinotype, XXXII, was published recently as the only known strain with a PaLoc located outside the usual chromosomal integration site (8). …”

Section: Overview Of Known Toxinotypesmentioning

confidence: 99%

An Update on Clostridium difficile Toxinotyping

2016

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cToxinotyping is a PCR-restriction fragment length polymorphism (RFLP)-based method for differentiation of Clostridium difficile strains according to the changes in the pathogenicity locus (PaLoc), a region coding for toxins A and B. Toxinotypes are a heterogenous group of strains that are important in the development of molecular diagnostic tests and vaccines and are a good basis for C. difficile phylogenetic studies. Here we describe an overview of the 34 currently known toxinotypes (I to XXXIV) and some changes in nomenclature.

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Section: Overview Of Known Toxinotypesmentioning

confidence: 99%

An Update on Clostridium difficile Toxinotyping

2016

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“…The main virulence factors of C. difficile are C. difficile toxin A (TcdA) and C. difficile toxin B (TcdB), which are encoded by the genes tcdA and tcdB, respectively (3,4). In addition, a separate binary toxin is produced by a small group of isolates with or without TcdA and/or TcdB (5,6), and it has been suggested that the binary toxin may play a part in the recurrence of C. difficile infection (CDI) (7). As the role of the binary toxin in CDI currently is not well understood, it has not become a common target for diagnostic assays.…”

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confidence: 99%

Evaluation of a New Automated Homogeneous PCR Assay, GenomEra C. difficile, for Rapid Detection of Toxigenic Clostridium difficile in Fecal Specimens

2013

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bWe evaluated a new automated homogeneous PCR assay to detect toxigenic Clostridium difficile, the GenomEra C. difficile assay (Abacus Diagnostica, Finland), with 310 diarrheal stool specimens and with a collection of 33 known clostridial and nonclostridial isolates. Results were compared with toxigenic culture results, with discrepancies being resolved by the GeneXpert C. difficile PCR assay (Cepheid). Among the 80 toxigenic culture-positive or GeneXpert C. difficile assay-positive fecal specimens, 79 were also positive with the GenomEra C. difficile assay. Additionally, one specimen was positive with the GenomEra assay but negative with the confirmatory methods. Thus, the sensitivity and specificity were 98.8% and 99.6%, respectively. With the culture collection, no false-positive or -negative results were observed. The analytical sensitivity of the GenomEra C. difficile assay was approximately 5 CFU per PCR test. The short hands-on (<5 min for 1 to 4 samples) and total turnaround (<1 h) times, together with the high positive and negative predictive values (98.8% and 99.6%, respectively), make the GenomEra C. difficile assay an excellent option for toxigenic C. difficile detection in fecal specimens.T oxin-producing Clostridium difficile is the most common cause of hospital-acquired and antibiotic-associated diarrhea (1, 2). The main virulence factors of C. difficile are C. difficile toxin A (TcdA) and C. difficile toxin B (TcdB), which are encoded by the genes tcdA and tcdB, respectively (3, 4). In addition, a separate binary toxin is produced by a small group of isolates with or without TcdA and/or TcdB (5, 6), and it has been suggested that the binary toxin may play a part in the recurrence of C. difficile infection (CDI) (7). As the role of the binary toxin in CDI currently is not well understood, it has not become a common target for diagnostic assays.CDI is prevalent in many hospitals and health care facilities throughout the world. It is associated with increases in hospitalization times and mortality rates, leading to augmented health care costs (2,6,8). In order to limit the transmission of C. difficile and to decrease the burden of CDI, rapid reliable detection of toxigenic C. difficile isolates and good infection prevention practices are required.Cytotoxigenic cultures and cytotoxin assays are considered standard diagnostic methods. These are sensitive but have several drawbacks, including long turnaround times and labor-intensive sample preparation and analysis, which limit their clinical utility (9-13). An alternative approach is the detection of C. difficile toxins or glutamate dehydrogenase (GDH) in stool samples by immunochromatographic antigen (IA) tests or enzyme immunoassays (EIAs) (14-16). These assays are rapid but are less sensitive and less specific than toxigenic cultures. Moreover, relying only on GDH detection reveals nothing about the toxigenic nature of the possible C. difficile isolates. To improve the detection of CDI using IA tests or EIAs, a two-step diagnostic algorithm has bee...

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“…This resulted in a specificity of 97% and a subsequent PPV of 51%, while remaining the high sensitivity of 95.8%. However, in the rare event a patient is colonized with a toxin A-negative, toxin B-positive C. difficile strain (26,27), the new strategy will not identify this strain. The test results of artus PCR showed lower inhibition rates than the in-house PCR, at 8% versus 5.3%, respectively; however, inhibition of the in-house PCR was overcome by adding the PCR enhancer BSA (28).…”

Section: Discussionmentioning

confidence: 99%

“…For CDI diagnosis, the use of a two-step algorithm is recommended (27). After a first sensitive test, which reliably classifies nondiseased patients, a more specific test is applied as a second test to discern true positives from false positives.…”

Section: Discussionmentioning

confidence: 99%

Detection of Clostridium difficile in Feces of Asymptomatic Patients Admitted to the Hospital

et al. 2017

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Recent evidence shows that patients asymptomatically colonized with Clostridium difficile may contribute to the transmission of C. difficile in health care facilities. Additionally, these patients may have a higher risk of developing C. difficile infection. The aim of this study was to compare a commercially available PCR directed to both toxin A and B (artus C. difficile QS-RGQ kit CE; Qiagen), an enzymelinked fluorescent assay to glutamate dehydrogenase (GDH ELFA) (Vidas, bioMéri-eux), and an in-house-developed PCR to tcdB, with (toxigenic) culture of C. difficile as the gold standard to detect asymptomatic colonization. Test performances were evaluated in a collection of 765 stool samples obtained from asymptomatic patients at admission to the hospital. The C. difficile prevalence in this collection was 5.1%, and 3.1% contained toxigenic C. difficile. Compared to C. difficile culture, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the C. difficile GDH ELFA were 87.2%, 91.2%, 34.7%, and 99.3%, respectively. Compared with results of toxigenic culture, the sensitivity, specificity, PPV, and NPV of the commercially available PCR and the in-house PCR were 95.8%, 93.4%, 31.9%, 99.9%, and 87.5%, 98.8%, 70%, and 99.6%, respectively. We conclude that in a lowprevalence setting of asymptomatically colonized patients, both GDH ELFA and a nucleic acid amplification test can be applied as a first screening test, as they both display a high NPV. However, the low PPV of the tests hinders the use of these assays as stand-alone tests.KEYWORDS Clostridium difficile, asymptomatic, carrier, diagnostics C lostridium difficile infection (CDI) is a leading cause of hospital-acquired diarrhea. The transmission of spores from symptomatic patients can spread C. difficile within health care facilities, with a subsequent development of more symptomatic patients and eventually clusters and outbreaks. However, recent data suggest that patients asymptomatically colonized with C. difficile also contribute to the spread of C. difficile spores to the environment and to other patients (1-3). Asymptomatic carriers shed spores into the environment to a lesser extent than CDI patients (3, 4), but by outnumbering the CDI patients, they can still play an important role in the transmission of the disease. This hypothesis has recently been supported in a Canadian study, where isolation of C. difficile-colonized patients significantly reduced the incidence of hospitalacquired CDI (5). A second new insight into the significance of asymptomatic colonization is that it may increase the risk of subsequent clinical disease in some colonized patients (6-10). Progression from colonization to CDI can be provoked by alterations of the microbiota and a subsequent decrease in secondary bile acids, which normally inhibit spore germination (11-13). But other factors, like preexisting antitoxin antibod-

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New types of toxin A-negative, toxin B-positive strains among clinical isolates of Clostridium difficile in Australia

Cited by 55 publications

References 33 publications

An Update on Clostridium difficile Toxinotyping

An Update on Clostridium difficile Toxinotyping

Evaluation of a New Automated Homogeneous PCR Assay, GenomEra C. difficile, for Rapid Detection of Toxigenic Clostridium difficile in Fecal Specimens

Detection of Clostridium difficile in Feces of Asymptomatic Patients Admitted to the Hospital

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