Evaluation of the VIDAS CDAB Kits for the Detection of the Clostridium difficile Toxins A and B / 대한임상미생물학회지

BACKGROUND: Since the emergence of variant Clostridium difficile strains that fail to produce detectable toxin A, diagnostic kits targeted to detect toxin A only showed a considerable rate of false negative results. The aim of this study was to evaluate a toxins A and B (toxins A/B) detection kit recently marketed in Korea, and to compare toxin positive rates before and after introduction of the new kit. METHODS: The results of 5,783 toxin A assays performed during the 7-year period from 2001 through 2007 were analyzed and compared them to the toxins A/B assay data of 519 samples obtained from January to June 2008 in a university hospital. An enzyme-linked fluorescent immunoassay for toxins A/B (VIDAS C. difficile Toxin A & B, bioMerieux SA, France: VIDAS CDAB) and PCR for toxin genes A/B were performed directly in 102 stool samples from hospitalized patients. RESULTS: The positive rates of toxin A assays tended downward annually from 2001 to 2007 (16.3%, 17.8%, 13.9%, 11.4%, 13.8%, 8.2%, and 5.8%, respectively), but increased to 12.1% in 2008 after changing to the toxin A/B detection kit. The concordant rate of the VIDAS CDAB kit with the PCR method was 82.4%. Compared to the PCR method, the sensitivity and specificity of the toxin A/B kit were 60.7% and 90.5% respectively. CONCLUSION: Testing kits for C. difficile toxin A only could result in a misdiagnosis more frequently than the testing kit for toxins A/B. The sensitivity of the newly launched toxin A/B detection kit from bioMerieux SA needs to be improved, but it showed a good specificity

Evaluation of Four Methods for Antimicrobial Susceptibility Testing of Helicobacter pylori in Routine Practice / 대한임상미생물학회지

BACKGROUND: We compared currently available four antimicrobial susceptibility test methods for H.pylori to find out a practical method suitable for testing a few strains of H.pylori at a time in the clinical microbiology laboratory. METHODS: With 37 clinical isolates of H.pylori, antimicrobial susceptibility tests were performed against amoxicillin (AMX), clarithromycin (CLR), and metronidazole (MTZ) using disk diffusion method with egg yolk emulsion (EYE) media, E test with EYE and Mueller Hinton blood agar plate (MH BAP), and modified broth microdilution methods (mBMD). RESULTS: The results of AMX and CLR showed a complete agreement between the four methods. For MTZ, however, a significant discrepancy was observed between the results obtained by the four methods. In four strains exhibiting high minimal inhibitory concentrations (MIC, > or =32 mg/L) to MTZ, category agreement was excellent, but correlation was not good in 13 strains with the MTZ MICs of 8 to 16 mg/L. In 20 strains with MTZ MICs between 0.25 mg/L and 4 mg/L, category agreement was excellent, but correlation between MICs or inhibitory zone diameters was not good. Etest EYE and Etest MH BAP methods showed a 100% agreement in the susceptibility category of MTZ. CONCLUSION: In routine practice, the most practical method for testing susceptibility of H.pylori to AMX and CLR seems to be the disk diffusion method with EYE or MH BAP. But for MTZ, a duplicate test using both Etest and disk diffusion test is recommended until more standardized, economical, and technically easier test methods become available.

A Case of Primary Intestinal T-Cell Lymphoma Involving Entire Gastrointestinal Tract: Esophagus to Rectum

Primary intestinal T-cell lymphoma is a rare disease entity, which is approximately 10% to 25% of intestinal lymphomas, and most of the lymphomas occur in the small intestine. We report here a case of a 56-year-old woman who has been suffering from chronic diarrhea and weight loss for 6 months. Abdominal CT scan and small bowel series showed diffuse wall thickening of the small bowel. Gastroscopic examination showed diffuse erythematous lesions on the esophagus and small gastric ulcerations on the antrum of the stomach, and colonoscopic examination also showed multiple punched-out ulcerations and erosions on the entire colon, including the sigmoid colon to the terminal ileum. Diffuse infiltration of CD 3 positive lymphoma cells was found on biopsy. The patient was diagnosed as primary intestinal T-cell lymphoma with diffuse involvement of the entire gastrointestinal tracts from the esophagus to the rectum. Although the patient received systemic combination chemotherapy and achieved partial response initially, the lymphoma relapsed repeatedly.

Comparison of Modified Broth Microdilution Method, E test, and Disk Diffusion Method for Antimicrobial Susceptibility Testing of Helicobacter pylori / 대한임상병리학회지

BACKGROUND: The emergence of metronidazole (MTZ) resistance among Helicobacter pylori (H. pylori) isolates has compromised the efficacy of the triple therapy. Therefore, special attention should be given toward reliable methods for determining the in vitro susceptibility. But susceptibility testing of H. pylori is not yet either standardized or routinely performed. The purpose of this study was to establish more reliable, but simple to perform and cost-effective antimicrobial susceptibility testing method. METHODS: With 135 clinical isolates of H. pylori, antimicrobial susceptibility tests for MTZ and clarithromycin (CLR) were performed by antibiotic gradient method (E test, AB BIODISK, Sweden) and disk diffusion method (disk method), and the results were compared with the reference modified broth microdilution method (broth method). RESULTS: Resistant rates of Korean isolates of H. pylori for MTZ and CLR were 46.2% and 2.2%, respectively. There was 100% agreements between the E test, disk method and the broth method for CLR. For MTZ, however, agreements between the results obtained by the three methods were variable. Between the E test and broth method, the agreements were 85.1% in terms of susceptibility categories, 80.5% between the disk and broth method, and 93.1% between the E test and disk method. CONCLUSIONS: Routine susceptibility testing of H. pylori to MTZ seems to be required in Korea. The broth method is recommended for MTZ until more accurate, simple and practical alternative method become available. For the CLR, the disk method is recommended, because it is reliable, simple, and economical.