אילמ"ר - האיגוד הישראלי למדעי המעבדה הרפואית

אילמ"ר - האיגוד הישראלי למדעי המעבדה הרפואית

כינוס שנתי ה-46 | 2012

פוסטרים להצגה בכינוס

EVALUATION OF THREE RAPID TESTS IN COMPARISON TO THE ELISA TOXIN A&B TEST FOR THE DIAGNOSIS OF TOXIGENIC CLOSTRIDIUM DIFFICILE INFECTION

Adi Kammer, Israela Avidor, Zoya Koifman, Hannah Sprecher, Yuval Geffen
Clinical Microbiology Laboratory, Rambam Medical Center, Haifa, 31096

 

Introduction: Clostridium difficile (CD) is a gram positive anaerobic bacterium, part of the normal intestinal flora. After treatment with antibiotics, CD may cause mild to severe diarrhea. CD Infection (CDI) is most common in hospitalized patients. The commonly used ELISA toxin A&B test, which detects CD toxins A&B has been reported to have low detection rates. In addition, new toxins, the binary toxin and the deletion mutation tcdC (NAP1) have been discovered in CD.


Objective: The aim of this study was to compare the ELISA test with three rapid tests for the detection of toxigenic CD in order to establish and evaluate a reliable algorithm for CD detection in stool specimens.


Methods: 249 stool specimens were collected from hospitalized patients between June-August 2011. The Wampole C. DIFFICILE TOX A/B II™ (Techlab, referred to as ELISA) for the detection of CD toxins A&B was compared to: 1) C. Diff QUIK CHEK COMPLETE (Techlab, referred to as QUIK), a rapid EIA for the simultaneous detection of CD glutamate dehydrogenase antigen (GDH), a marker for CD and toxins A&B, 2) GeneXpert C. Difficile (Cephied) a real time PCR, nucleic acid amplification test (NAAT) system, and 3) Illumigene C. difficile Assay (Meridian Bioscience), A Loop-Mediated Isothermal Amplification (LAMP) NAAT system. Results were reported according to a work flow algorithm, comprised of an initial screening of all samples with the QUIK test, followed by NAAT test for the GDH+/Toxin(-) samples.


Results: The ELISA test detected only 15/24 (62.5%) positive samples (37.5% FN). The QUIK test detected 12/24 positive samples (GDH+/Toxin+). 22/24 samples were GDH+/Toxin(-), and 50% of these samples were verified as true positives by both GeneXpert and Illumigene. The GeneXpert, which examines the presence of 3 targets: toxin B, binary toxin and tcdC mutation, detected all 24/24 positive stools for the presence of Toxin B gene (100% sensitivity), 8 had binary toxin and 6 were also NAP1 positive. The Illumigene system, detected 21/21 positive stool samples (100% sensitivity).


Conclusions:

  • The ELISA assay had low sensitivity (62.5%) for the detection of CD toxin, with 37.5% FN and 2% FP.
  • The QUIK test detected toxin B in only 50% of the positive samples. However all positive samples, as detected by one of the NAAT methods, were at least positive for GDH, which could have been detected by the suggested work flow algorithm.
  • GeneXpert system showed 100% sensitivity with 0.4% FP.
  • Illumigene system showed 100% sensitivity with 0% FP.
  • The detection of the new toxin genes by the GeneXpert is important in detecting outbreaks of an epidemic caused by the NAP1 strain.
  • Clinical microbiology laboratories should consider adopting this algorithm for low cost but accurate diagnosis of CDI that is crucial to the overall management of this nosocomial infection.
לתכנית הכנס     חזרה לריכוז הפוסטרים 2012
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