Division of Medical Microbiology, Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Anaerobe. 2011 Aug;17(4):170-4. doi: 10.1016/j.anaerobe.2011.01.002. Epub 2011 Mar 3.
Clostridium difficile (C. difficile) causes 25-30% of cases of antibiotic associated diarrhea and most cases of pseudomembranous colitis. Patients presenting with diarrhea after hospitalization for 3 or more days should be tested for C. difficile. There are many options available for testing, each of which has inherent advantages and disadvantages. Most laboratories perform toxin testing using an enzyme immunoassay method. In general these tests have sensitivities ranging from 60 to 70% and specificities of 98%. When using these methods, symptomatic patients with negative tests should be tested by another more sensitive method. Until recently, cell culture cytotoxicity neutralization assays (CCNAs) were considered the gold standard in the U.S. A two-step algorithm using an EIA for glutamate dehydrogenase detection followed by testing positives using CCNA, offered an improved alternative until the availability of molecular assays. Although early studies that compared the GDH assay to CCNA demonstrated high sensitivity and negative predictive values, more recent comparisons to toxigenic culture and PCR have shown the sensitivity to be in the mid to high 80's. When testing using a sensitive assay, repeat testing is not cost-effective. Outbreaks caused by a toxin variant epidemic strain have renewed interest in bacterial culture. Toxigenic culture has emerged as the new gold standard against which newer assays should be compared. However, there is no agreed upon standard method for culture performance. At least 4 FDA cleared nucleic acid amplification assays are available to clinical laboratories and several of these have been well evaluated in the literature. Because these assays detect a gene that encodes toxin and not the toxin itself it is important that laboratories test only patients with diarrhea. These molecular assays have been shown to be superior to toxin EIAs, CCNA and 2-step algorithms, but not to toxigenic culture. More studies are needed to assess the impact of molecular tests on treatment and nosocomial spread of Clostridium difficile infections.
艰难梭菌（C. difficile）导致 25-30%的抗生素相关性腹泻和大多数伪膜性结肠炎病例。住院 3 天以上后出现腹泻的患者应进行艰难梭菌检测。有许多检测方法可供选择，每种方法都有其内在的优点和缺点。大多数实验室使用酶免疫测定法进行毒素检测。一般来说，这些检测的敏感性在 60%至 70%之间，特异性为 98%。使用这些方法时，阴性检测的症状性患者应使用另一种更敏感的方法进行检测。直到最近，细胞培养细胞毒性中和测定（CCNA）仍被认为是美国的金标准。两步法使用谷氨酸脱氢酶检测的酶免疫测定法，然后使用 CCNA 检测阳性，在分子检测方法出现之前提供了一种改进的替代方法。尽管比较 GDH 检测与 CCNA 的早期研究表明其具有高敏感性和阴性预测值，但最近与产毒培养和 PCR 的比较表明，其敏感性在 80 到 90 之间。使用敏感检测方法时，重复检测不具有成本效益。由毒素变异流行株引起的暴发重新引起了对细菌培养的兴趣。产毒培养已成为新的金标准，应将新的检测方法与之进行比较。然而，对于培养性能，尚无公认的标准方法。至少有 4 种已获得 FDA 批准的核酸扩增检测方法可用于临床实验室，其中几种方法在文献中已得到很好的评估。由于这些检测方法仅检测携带腹泻的患者，因此仅检测携带腹泻的患者。这些分子检测方法已被证明优于毒素 EIA、CCNA 和两步法，但不如产毒培养。需要更多的研究来评估分子检测对艰难梭菌感染的治疗和医院内传播的影响。
