Avaliação de métodos diagnósticos para a infecção por Clostridium difficile em potros e seres humanos

Abstract

Clostridium difficile has been identified out as an important pathogen in foals and human causing nosocomial diarrhea and pseudomembranous colitis. The aim of this study was to compare the isolation followed by the typification by Multiplex PCR, three kits of ELISA and a kit of qRT-PCR commercially available, for the diagnosis of C. difficile. The parameters evaluated were sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) against to cytotoxicity assay (CTA) by using stool samples of foals and humans. A total of 104 stool samples from foals, 10 (9.6%) were considered positive at CTA, considered the test "gold standard", and 12 (11.5 %) considered positive by isolation and Multiplex PCR that had 70% of sensitivity, 94.7% of specificity, positive predictive values of 58.3% and negative predictive values of 96.7%. The three kits of ELISA were able to identify the positive samples at CTA showing 100% of sensitivity, specificity greater than 95%, positive predictive value (PPV) between 71% and 91% and negative predictive value (NPV) of 100%. A total of 78 samples of feces from humans, 18 (23.07%) were considered positive at CTA and 13 (16.66%)were identified by isolation and Multiplex PCR presenting 72.22% of ensitivity, 81.66% of specificity, positive predictive values of 54.16% and negative predictive values of 90.74 %. Two of three kits of ELISA tested were able to identify 13 (16.66%) samples also positive at CTA and presenting sensitivity of 72.22%. The other kit identified 14 samples presenting 77.77% of sensitivity. The specificity of the three kits ELISA was between 93 and 100%. The PPV was above 76% and the NPV above 90%. The qRT-PCR used for samples from humans, presenting a sensitivity of 61.11%, specificity of 98.30%, positive predictive value of 91.11% and negative predictive value of 89.23%. All ELISA kits were suitable for diagnosis of CDI in foals due to the high sensitivity and specificity. Already, the isolation followed by MultiplexPCR showed low sensitivity, it is not suitable for diagnosis of CDI in foals. All methods employed in this study of stool samples from human showed low sensitivity, which could result in an increase in the number of false negative results, this contributes to the spread of spores in environment and possible infection of susceptible patients.