Evaluation of six commercial assays for the rapid detection of Clostridium difficile toxin and/or antigen in stool specimens.

OBJECTIVE: To evaluate six commercially available assays for the detection of Clostridium difficile toxin and/or antigen in stool samples: one latex agglutination test (Culturette brand CDT, Becton Dickinson), two ELISAs (Culturette brand Toxin CD, Becton Dickinson, and Ridascreen C. difficile Toxin A/B, R-biopharm), two chromatographic assays (Clearview C. difficile A, Oxoid, and ColorPac Toxin A, Becton Dickinson) and one enzyme immunoassay for the simultaneous detection of C. difficile common antigen and toxin A (Triage C. difficile Panel, Biosite). METHODS: Over a period of 3 months, 366 liquid or semi-liquid stool samples were tested using cell-culture cytotoxin assay as standard, ethanol shock stool culture and latex agglutination (Culturette brand CDT). Of these, 78 samples, positive with at least one of these three methods, and 98 randomly selected negative samples were further evaluated using the other five kits. PCR was also performed on positive cultures to confirm the presence of toxin A and B genes. RESULTS: Triage C. difficile Panel had the best sensitivity (95%), followed by Clearview C. difficile and ColorPac Toxin A (both 89%), Culturette brand Toxin CD (73%), Ridascreen C. difficile Toxin A/B (57%) and Culturette brand CDT (23%). For Triage, the sensitivity of C. difficile antigen detection was 93%, and the sensitivity of toxin detection was lower (77%). Most false-positive results were obtained with the Triage C. difficile Panel (25 specimens) and Clearview C. difficile A (20 specimens). Culturette brand CDT had the best specificity (99%); followed by Ridascreen C. difficile Toxin A/B (97%), Culturette brand Toxin CD (95%), ColorPac Toxin A (89%), Clearview C. difficile A (83%) and Triage C. difficile Panel (75%). The positive predictive values ranged from 68% to 94%, and the negative predictive values from 83% to 98%. CONCLUSIONS: The sensitivity is much higher for Triage and the two new chromatographic assays than for the conventional EIAs. These tests also have a high negative predictive value. For Triage, C. difficile antigen-positive, toxin A-negative results can be obtained; the clinical value of these must be established by additional studies. Overall, the new-generation assays are still less sensitive than the cytotoxin assay; however, they provided same-day results, could be used as a screening test and may be useful in laboratories without tissue-culture facilities. Our results do not allow the recommendation of one single assay for the diagnosis of C. difficile-associated diarrhea. It remains the case that laboratory results must be correlated and interpreted with the clinical presentation of the patient.

Comparative in vitro activity of cefepime against strains isolated from intensive care and haematology patients.

The aim of the study was to evaluate cefepime, a "fourth generation" cephalosporin, for its in vitro activity in comparison with 5 other broad spectrum antibiotics against clinical isolates from ICU and haematology patients. The strains were isolated from blood (8%), lower respiratory tract (41%), upper respiratory tract (14%), urine (20%) and other sites (17%). They were divided into: 28 non-inducible Enterobacteriaceae, 35 inducible Enterobacteriaceae, 20 non-fermenters, 10 S. aureus and 10 Streptococcus spp. The MIC-values were determined by E-test. Overall, the rank order of susceptibility was cefepime (93%), imipenem (90%), piperacillin-tazobactam (81%), ciprofloxacin (79%), ceftriaxone (75%) and ceftazidime (74%). Only cefepime was able to inhibit all inducible Enterobacteriaceae. Against Pseudomonas aeruginosa, cefepime had the same activity as ceftazidime. With the exception of ceftazidime (65%), all beta lactams demonstrated good activity against Gram positive cocci. The excellent activity against most Gram negative and Gram positive pathogens suggests that cefepime may be useful in the treatment of serious infections in the described patient population.

Significance of qualitative polymerase chain reaction combined with quantitation of viral load in the diagnosis and follow-up of cytomegalovirus infection after solid-organ transplantation.

Quantitative PCR was evaluated in the monitoring of patients with ongoing posttransplantation cytomegalovirus (CMV) infection and antiviral therapy, compared to leukoDNAemia and serology. From January 1998 until May 1999, 61 patients were followed up weekly during 3 months after transplantation by a qualitative PCR. The quantitative PCR was performed on plasma samples from 21 selected patients, of whom 12 had a primary infection and 9 a reactivation or reinfection. Analysis of the viral load differences showed that the viral loads in patients with a primary infection were significantly higher than viral loads in patients with a reactivation (p < 0.01). Based on the results of our study, we can state that qualitative PCR is a good marker for initiating preemptive therapy. In addition, viral quantitation is clinically useful for accurate diagnosis of established CMV disease, and monitoring of antiviral therapy.