Comunicación presentada en 31st Annual Congress of the European Society of Mycobacteriology (ESM 2010)

4 de julio de 2010

Bezos J., Aranaz A., Romero B., Alvarez J., Casal C., Moya N., Lozano F., Mateos A. y Dominguez L.

The gamma-interferon assay is as a useful tool (together with the tuberculin test) for the diagnosis of tuberculosis in cattle and goats. In these experiments, we have evaluated the effect of factors such as phenol concentration and dialysis of PPDs, delay in processing samples and use of single or duplicate results on the performance of the assay. Moreover, we have evaluated the influence of tuberculin test on gamma-interferon production in infected animals. Finally, presence of lesions and microbiological results have been correlated with the production of gamma-interferon. To assay the effect of phenol concentration, bovine and avian PPDs with three different phenol concentrations (0.1, 0.3 and 0.5%) were prepared and results were compared with those obtained using dialyzed 0.5% phenol PPDs. For the study of the effect of a delay in blood culture, samples were stimulated within first 8 hours and 16 and 24 hours after collection and results were compared. Gamma-interferon assay was performed in duplicate to study differences between repeated samples. Finally, a group of goats were necropsied and lesion score was calculated and correlated with the gamma-interferon release. Results using two cut-off points (0.05 and 0.1) were analyzed using SPSS and WINPEPI software. Proportion of positive samples were lower in samples stimulated with dialyzed PPDs: using the 0.05 cut-off point, significant differences were observed between dialyzed PPD and non-dialyzed 0.5% phenol PPD (p<0.1). Using a threshold of 0.1, significant differences (p<0.05) were also obtained. Analysis of variance revealed significant differences between results with blood stimulated within the first 8 hours compared with those stimulated after 16 and 24 hours post-collection. When the test was performed in duplicate, the number of positives was very similar in both runs of the test, and concordance between outcomes was very high (kappa>0.85). Moreover, differences in the correlation between lesion score and gamma-interferon release based on the antigen assayed for stimulation were observed. These findings can improve the application of gamma-interferon tests for the diagnosis of tuberculosis in cattle and goats.

	Servicio de Micobacterias (MYC). Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).
	Departamento de Sanidad Animal. Facultad de Veterinaria. Universidad Complutense (UCM).

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