Comparison of three Clostridium difficile toxin assays, C: difficile GDHantigen EIA, C. difficile GDH-PCR, bacterial culture and cytotoxicity assay for the diagnosis of C. difficile-associated diarrhoea

K. Sachs, G. Ackermann, A.C. Rodloff (Leipzig, D)
Objectives: Clostridium difficile- associated diarrhoea (CDAD) remains the leading cause of nosocomial-acquired diarrhoea. Prolonged hospital stay and diagnostic and therapeutic procedures due to CDAD cause additional costs. The present study had the aim to assess the value of different assays to detect C. difficile infections among patients with nosokomial diarrhoea.
Methods: 377 stool samples from patients from a tertiary care hospital were investigated for C. difficile toxins using three Toxin A/B assays (RIDASCREEN, r-biopharm; Premier C. difficile Toxin A&B, Meridian; ImmunoCard Toxins A&B, Meridian), a C. difficile GDH antigen EIA (C. DIFF CHEK, Techlab), C. difficile GDH PCR, stool culture and cytotoxicity assay. Toxin assays and GDH-antigen EIA were performed according to the instructions of the manufacturer. Stool culture was done using cycloserin-cefoxitin-fructose agar.
Results: The toxin A/B positive results received from the three toxin assays were as follows: RIDASCREEN, 55 (14,6%); Premier Toxin A&B, 87 (23%); Immunocard Toxin A&B, 106 (28%). GDH-antigen was detected in 121 (32%) stool samples using the C. DIFF CHEK and in 100 (26,5%) specimens by PCR. C. difficile grew from 66 stool samples (17,5%). Specific cytopathic effect in cell culture due to toxin B of C. difficile was detected in 137 (36,3%) stool preparations.
Conclusion: Higher sensitivity and faster protocols make new C. difficile tests more attractive for routine diagnostics. The performance of the Immunocard Toxin A&B assay and the two GDH-antigen tests were excellent. Nevertheless, C. difficile culture is still necessary for further investigations as for toxigenicity, antimicrobial susceptibility and typing.
15th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID)
2-5 April 2005 — Copenhagen, Denmark