Evaluation of two DNA amplification PCR tests for the diagnosis of Clostridium difficile infection

Introduction. Clostridium Difficile (CD) usually is present in the gut of healthy subjects without giving any disease. As a consequence of various stress, including antibiotic therapy, CD can replicate and produce A and B toxins that induce diarrhoea.The finding of A and B toxins is a landmark for diagnosis of CD infection. Methods. 60 stool samples have been tested for CD presence. All the samples have been tested for the glutamate dehydrogenase (GDH) presence.The GDH positive samples have been tested with two rapid tests to evidence A and B toxins. Moreover, 18 positive and 3 negative GDH samples have been examined by means of cultivation tests and using two nested PCR (n-PCR) commercial kits (Neomed, Rho, Italy) to amplify the CD toxin coding gene tcdC and tcdB. Results.Among 60 examined samples, 52 (45%) were GDH positive, and, among these, 46 (76%) and 37 (62%) resulted respectively positive for both AB and for only A CD toxin using screening tests.Among the 18 GDH positive samples tested, 14 were positive for tcdC and tcdB n-PCR, while all the 3 GDH negative samples were confirmed as negative. The isolation in colture was positive in 16 of the GDH positive and in 2 of the 3 GDH negative samples. Conclusions.These data suggest that the GDH test is a useful screening method that must be associated to a confirmatory assay.The search of CD toxin coding gene by n-PCR seems to be a sensitive and specific method to assess the infection with toxins producing CD.