Lyerly D M, Neville L M, Evans D T, Fill J, Allen S, Greene W, Sautter R, Hnatuck P, Torpey D J, Schwalbe R
TechLab, Inc., Corporate Research Center, Blacksburg, Virginia 24060, USA.
J Clin Microbiol. 1998 Jan;36(1):184-90. doi: 10.1128/JCM.36.1.184-190.1998.
Clostridium difficile, the primary cause of nosocomial diarrhea in the United States and many other industrialized countries, is recognized as a major health concern because of its ability to cause severe intestinal disease leading to complications such as relapses and infections due to vancomycin-resistant enterococci. The disease results from two toxins, toxins A and B, produced by this pathogen. In this study, we evaluated the TOX A/B TEST, a new 1-h enzyme immunoassay (EIA) that detects toxins A and B. We compared the test with the tissue culture assay, which is recognized as the "gold standard" for C. difficile testing. Evaluations were performed in-house at TechLab, Inc. (Blacksburg, Va.) and off-site at four clinical laboratories. Of 1,152 specimens tested, 165 were positive by the TOX A/B TEST and tissue culture and 973 were negative by both tests. The sensitivity and specificity were 92.2 and 100%, respectively. The positive and negative predictive values were 100 and 98.6%, respectively, and the correlation of the TOX A/B TEST with tissue culture was 98.8%. When discrepant samples were resolved by culture, the sensitivity and specificity were 93.2 and 98.9%, respectively. The positive and negative predictive values were 100 and 98.8%, respectively, with a correlation of 99.0%. There were no specimens that were positive by the TOX A/B TEST and negative by tissue culture. Fourteen specimens were negative by the TOX A/B TEST but positive by tissue culture. Of these, two were negative by toxigenic culture, five were positive by toxigenic culture, and seven were not available for further testing. There were no indeterminate results, since the test does not have an indeterminant zone. In a separate study, 102 specimens that were positive by tissue culture and the TOX A/B TEST were examined in toxin A-specific EIAs. Two specimens that presumptively contained toxin A-negative, toxin B-positive (toxA-/toxB+) isolates were identified. One specimen was from a patient with a clinical history consistent with C. difficile infection. Isolates obtained from these specimens by selective culture on solid media and in broth tested toxA-/toxB+ when grown in brain heart infusion dialysis flasks, which stimulate in vitro production of both toxins. Our findings show that the TOX A/B TEST is suitable as a diagnostic aid for C. difficile disease because it correlates well with tissue culture and detects isolates that may be missed with toxin A-specific EIAs.
艰难梭菌是美国及许多其他工业化国家医院内腹泻的主要病因，因其能够引发严重肠道疾病并导致诸如复发以及耐万古霉素肠球菌感染等并发症，所以被视为一个重大的健康问题。该疾病由这种病原体产生的两种毒素，即毒素A和毒素B引起。在本研究中，我们评估了TOX A/B TEST，这是一种新型的1小时酶免疫测定法（EIA），用于检测毒素A和毒素B。我们将该检测方法与组织培养检测法进行了比较，组织培养检测法被公认为艰难梭菌检测的“金标准”。评估在TechLab公司（弗吉尼亚州布莱克斯堡）内部以及四个临床实验室现场进行。在检测的1152份标本中，165份通过TOX A/B TEST和组织培养检测为阳性，973份两种检测均为阴性。灵敏度和特异性分别为92.2%和100%。阳性预测值和阴性预测值分别为100%和98.6%，TOX A/B TEST与组织培养的相关性为98.8%。当通过培养解决有差异的样本时，灵敏度和特异性分别为93.2%和98.9%。阳性预测值和阴性预测值分别为100%和98.8%，相关性为99.0%。没有标本通过TOX A/B TEST检测为阳性而通过组织培养检测为阴性。14份标本通过TOX A/B TEST检测为阴性但通过组织培养检测为阳性。其中，两份通过产毒培养检测为阴性，五份通过产毒培养检测为阳性，七份无法进行进一步检测。没有不确定的结果，因为该检测没有不确定区域。在另一项研究中，对102份通过组织培养和TOX A/B TEST检测为阳性的标本进行毒素A特异性EIA检测。鉴定出两份推测含有毒素A阴性、毒素B阳性（toxA-/toxB+）分离株的标本。一份标本来自一名临床病史与艰难梭菌感染相符的患者。通过在固体培养基和肉汤中进行选择性培养从这些标本中获得的分离株，当在脑心浸液透析瓶中生长时检测为toxA-/toxB+，脑心浸液透析瓶可刺激两种毒素的体外产生。我们的研究结果表明，TOX A/B TEST适合作为艰难梭菌疾病的诊断辅助手段，因为它与组织培养相关性良好，并且能够检测出可能被毒素A特异性EIA遗漏的分离株。
