Comparison of Toxin A Enzyme Linked Fluorescence Assay and Latex Agglutination based on Clostridium difficile culture and Toxin A and B PCR assay

Shin, Bo Moon; Lee, Eun Joo

Abstract

BACKGROUND
Clostidium difficile is one of the most important pathogens responsible for nosocomial diarrhea; therefore, we compared the efficacy of laboratory tests for diagnosing C. difficile diarrhea.
METHODS
We evaluated 107 stool specimens using a latex agglutination test (LA) (BD CDT, Culturette CDT, Becton, Dickison and Company, USA) and an enzyme linked fluorescent immunoassay (ELFA) (VIDAS C. difficile Toxin A II, Bio-Merieux sa, Marcy-l'Etoile, France). Stool specimens were cultured using cycloserine cefoxitine fructose agar in anaerobic condition. For identification of C. difficile, spore stain and Vitek ANA identification card (Bio-Merieux sa) were used. Toxin A and toxin B genes were analysed by PCRs using primers NK3-NK2 and NK104N-K105 respectively.
RESULTS
The concordance rate between LA and ELFA was 68.2%. Based on the culture results, the sensitivity/specificity of LA and ELFA were 54.8%/100% and 17.8%/100%, respectively. The positive rates of toxin A and B genes were both 90.4%(66/73). Based on the results of PCR assays for toxin A and B genes, the sensitivity/specificity of LA and ELFA were 37.9%/85.7% and 19.7%/100%, respectively.
CONCLUSION
Based on C. difficile culture and toxin A and B gene PCR results, the sensitivity of LA was apparently higher than that of ELFA. However, it should not be simply estimated that ELFA has lower capability for detecting toxin A of C. difficile because the possibility of emerging variant strains of C. difficile could not be ruled out. The prevalence of toxigenic strains of C. difficile including variant strains should be studied in Korea.