Legaria María C, Rollet Raquel, Di Martino Ana, Castello Liliana, Barberis Claudia, Rossetti María A, Guardati María C, Fernández Canigia Liliana, Carloni Graciela, Litterio Mirta, Rocchi Marta, Anchart Eduardo G, Trejo Fernando M, Minnaard Jessica, Klajn Diana, Predari Silvia C
Subcomisión de Bacterias Anaerobias de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas - Asociación Argentina de Microbiología, Ciudad Autónoma de Buenos Aires (CABA), Argentina; Hospital General de Agudos Dr. Enrique Tornú, CABA, Argentina.
Subcomisión de Bacterias Anaerobias de la Sociedad Argentina de Bacteriología, Micología y Parasitología Clínicas - Asociación Argentina de Microbiología, Ciudad Autónoma de Buenos Aires (CABA), Argentina; Hospital de Infecciosas Dr. Francisco Javier Muñiz, CABA, Argentina.
Rev Argent Microbiol. 2018 Jan-Mar;50(1):36-44. doi: 10.1016/j.ram.2017.01.002. Epub 2017 Oct 6.
The best laboratory diagnostic approach to detect Clostridioides [Clostridium] difficile infection (CDI) is a subject of ongoing debate. With the aim of evaluating four laboratory diagnostic methods, 250 unformed stools from patients with suspected CDI submitted to nine medical center laboratories from November 2010 to December 2011, were studied using: (1) an immunochromatographic rapid assay test that combines the qualitative determination of glutamate dehydrogenase (GDH) plus toxins A and B (QAB), the CDIFF QUIK CHEK COMPLETE assay; (2) an enzyme immunoassay for qualitative determination of toxins A and B, the RIDASCREEN™ C. difficile Toxin A/B assay (RAB); (3) a PCR for the toxin B gene assay (PCR); and (4) the toxigenic culture (TC). C. difficile isolates from direct toxin negative stools by QAB, RAB and PCR were evaluated for toxigenicity by the same direct tests, in order to assess the contribution of the TC (QAB-TC, RAB-TC, PCR-TC). A combination of the cell culture cytotoxicity neutralization assay (CCCNA) in stools, and the same assay on isolates from direct negative samples (CCCNA-TC) was considered the reference method (CCCNA/CCCNA-TC). Of the 250 stools tested, 107 (42.8%) were positive by CCCNA/CCCNA-TC. The GDH and PCR/PCR-TC assays were the most sensitive, 91.59% and 87.62%, respectively. The QAB, RAB, QAB/QAB-TC and RAB/RAB-TC had the highest specificities, ca. 95%. A negative GDH result would rule out CDI, however, its low positive likelihood ratio (PLR) of 3.97 indicates that a positive result should always be complemented with the detection of toxins. If the RAB, QAB, and PCR assays do not detect toxins from direct feces, the toxigenic culture should be performed. In view of our results, the most accurate and reliable methods to be applied in a clinical microbiology laboratory were the QAB/QAB-TC, and RAB/RAB-TC, with PLRs >10 and negative likelihood ratios <0.30.
检测艰难梭菌感染（CDI）的最佳实验室诊断方法一直是个有争议的话题。为了评估四种实验室诊断方法，我们对2010年11月至2011年12月期间提交给九个医学中心实验室的250份疑似CDI患者的不成形粪便进行了研究，采用了以下方法：（1）一种免疫层析快速检测法，该方法结合了谷氨酸脱氢酶（GDH）以及毒素A和B的定性测定（QAB），即CDIFF QUIK CHEK COMPLETE检测法；（2）一种用于毒素A和B定性测定的酶免疫测定法，即RIDASCREEN™艰难梭菌毒素A/B检测法（RAB）；（3）一种针对毒素B基因的聚合酶链反应检测法（PCR）；（4）产毒培养法（TC）。对通过QAB、RAB和PCR检测直接毒素呈阴性的粪便中分离出的艰难梭菌菌株，采用相同的直接检测方法评估其产毒性，以评估TC（QAB-TC、RAB-TC、PCR-TC）的作用。粪便中的细胞培养细胞毒性中和试验（CCCNA）以及对直接阴性样本分离物进行的相同试验（CCCNA-TC）的组合被视为参考方法（CCCNA/CCCNA-TC）。在检测的250份粪便中，107份（42.8%）通过CCCNA/CCCNA-TC检测呈阳性。GDH和PCR/PCR-TC检测法最为敏感，分别为91.59%和87.62%。QAB、RAB、QAB/QAB-TC和RAB/RAB-TC具有最高的特异性，约为95%。GDH检测结果为阴性可排除CDI，然而，其较低的阳性似然比（PLR）为3.97，表明阳性结果应始终辅以毒素检测。如果RAB、QAB和PCR检测法未从直接粪便中检测到毒素，则应进行产毒培养。鉴于我们的结果，临床微生物实验室中应用的最准确可靠的方法是QAB/QAB-TC和RAB/RAB-TC，其PLR>10且阴性似然比<0.30。
