RESUMO
Mycobacterium avium subsp. paratuberculosis which is more commonly referred to as MAP is the causative agent of Johnes's disease in ruminants. While cultivation of MAP from faecal samples remains the reference standard diagnostic test for the disease, faecal culture is expensive, slow and not widely available in Ireland. The current study evaluated three commercial kits that combine both DNA extraction and real-time PCR amplification of specific targets for direct MAP detection in cattle faeces. In total, 100 positive samples were tested which consisted of 25 high shedders, 25 medium shedders, 25 low shedders and 25 very low shedders. Also included were 100 negative faecal samples obtained from two Irish herds known to be free of Johne's disease. The kits evaluated in this study showed significant differences in identifying MAP DNA from animals shedding various concentrations of the bacterium. Kit C had the highest specificity, followed by kits B and A. Sensitivity in kits A, B and C was 73.5%, 81% and 93%, respectively, and specificity was 99%, 97% and 100%, respectively. Sensitivity decreased with lower concentrations of MAP in faeces but this was more significant for kits A and B than for kit C. The results of this study demonstrate that PCR can provide an accurate and rapid detection of MAP faecal shedding and kit C was selected for further evaluation of the role of PCR in the confirmation of animal infection in cattle.
Assuntos
Doenças dos Bovinos/diagnóstico , Mycobacterium avium subsp. paratuberculosis/genética , Paratuberculose/diagnóstico , Animais , Bovinos , Doenças dos Bovinos/microbiologia , Indústria de Laticínios , Fezes/microbiologia , Feminino , Mycobacterium avium subsp. paratuberculosis/isolamento & purificação , Paratuberculose/microbiologia , Kit de Reagentes para Diagnóstico/veterinária , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Sensibilidade e EspecificidadeRESUMO
Three rapid methods, an impedance method (Malthus 2000 Analyzer), a colorimetric DNA hybridization method (Gene-Trak) and a post-enrichment enzyme-linked immunosorbent assay (Salmonella-Tek) were compared with conventional culture for the detection of Salmonella in poultry feeds, and in fluff and dust samples from poultry housing. The percentage positive samples for Salmonella by each of the methods were 25.5% for conventional culture, 38.4% for the Malthus, 28.9% for the Gene-Trak and 28.5% for the Salmonella-Tek. By any method 60/153 (39.2%) of the samples tested were positive on confirmed culture.