Development and Validation of an Immunohistochemical Method for Diagnosis of Bovine Tuberculosis in Formalin-Fixed, Paraffin-Embedded Tissues

The objective of the study was to develop an indirect Immunoperoxidase Method for bovine tuberculosis diagnosis in formalin fixed, paraffin embedded tissues and its validation compared to mycobacterial isolation and Ziehl Neelsen staining. About of 33 bovine lymph nodes with isolation of Mycobacterium bovis and 11 negative lymph nodes from tuberculosis free ranches were used. Sections of all lymph nodes examined were stained with Ziehl Neelsen and Immunohistochemistry (IHC). Rabbit anti-M. bovis polyclonal antibodies and horse anti-rabbit were used as primary and secondary antibodies. The immunologic reaction was detected with an immunoperoxidase DAB Method and cotuaterstained with hematoxylin. Results show complete agreement between Immunohistochemistry and mycobacterial culture. From the 33 positive isolation cases, all of them (100%) were positive by IHC. From the 11 negative cases, all of them were negative to Mycobacterium by IHC. Regarding Ziehl Neelsen of the 33 positive isolation cases, 30 (90.9%) had acid-fast bacilli and from the 11 negative isolation cases none had acid fast bacilli. Results show that IHC represents a fast, sensitive and specific diagnostic tool for bovine tuberculosis in formalin fixed, paraffin embedded tissues allowing simultaneous observation of tissue lesions and antigens.