Date of Award
Masters of Science (Research)
Dr David Clancy
Clostridium difficile is one of the most common causes of antibiotic associated diarrhoea. The presence of C difficile in stool samples may be detected by a variety of means including enzyme immunoassays and culture. Enzyme immunoassays detect the presence of the toxins produced by the organism, toxin A and/or toxin B, but are known to lack sensitivity. The aim of this study was to compare the commercial ELISA assay currently used for the detection of C difficile toxins in Waterford Regional Hospital to culture for the organism to selective media. To compare the sensitivity of the two methods serial dilutions of a C difficile Ribotype 027 isolate were tested by culture and the toxin assay, and culture was determined to be the more sensitive method. 497 clinical stool samples were tested for C. difficile, 39 were positive by both culture and the toxin assay, 47 were positive by culture alone and 8 were positive by the toxin assay alone, giving an overall prevalence rate of 19%. 91% of samples were from hospital inpatients and 36% of positive samples were from patients in the 75 to 85 age bracket. The 86 C. difficile isolates were tested for toxin production, 60 isolates were toxin producers while 26 were toxin non-producers. 32 of the 60 toxin producing isolates had been negative by original stool toxin analysis, 28 had been positive. 11 of the 26 toxin non-producing isolates had been positive on original stool toxin analysis, 15 had been negative. 36 stool samples which had been toxin A/B positive either from stool and/or culture were tested for the presence of toxin A to determine if toxin A-negative, B-positive (A“B^) strains were present, 25 of these samples were negative for toxin A giving a prevalence rate of 69.4% for C. difficile toxin A"B^ strains. Antimicrobial susceptibility testing was performed on all cultured isolates and on a C. difficile Ribotype 027 isolate. 17 clindamycin-resistant A"B^ strains were found. None of the isolates had the same antibiogram as the Ribotype 027 isolate. This along with the low prevalence of this ribotype in Ireland suggests that Ribotype 027 is not present in the patient population of Waterford Regional Hospital. Genotypic analysis was carried out using the Automated Riboprmter (DuPont Qualicon™). Analysis indicated that the EcoRl restriction enzyme in combination with ribotyping produced poor resolution for genotypic analysis of C difficile.
Dennehy, Rebecca, "Clostridium difficile: Comparative Evaluation of Two Detection Techniques and Characterisation of Clinical Isolates." (2008). Theses [online].
Available at: https://sword.cit.ie/allthe/746