Demonstration of mycobacterium bovis in cattle via molecular and cytohistopathological diagnostic tecniques and comparison of the results

Abstract

In this study the detection of Mycobacterium bovis with classical and molecular techniques and comparisons of the test results in the thirty slaughtered cattle positive to intradermal tuberculin test (PPD) was aimed. The classical methods include macroscopic examination of the organs, microscopic examination of tissues and blood samples that were stained by HE, ZN, immunohistochemistry and immunocytochemistry and PCR as molecular investigation. Characteristic tubercle development was observed in 26 animals' macroscopic examination yet 27 and 20 cases were found compatible with tuberculosis in HE and ZN respectively. Tuberculosis positive results were also obtained from lungs, mediastinal lymph nodes and liver via immunohistochemistry (IHC), PCRtissue, immunocytochemistry of the buffy coat (ICCbc) and PCR of the buffy coat (PCRbc) in 26, 18, 3 and 14 cows respectively. The agents were observed extracytoplasmically and intracytoplasmically in macrophages, giant cells, lymphocytes and fibrocytes in IHC. ICCbc positivity was observed within the cytoplasm of mononuclear leukocytes. Furthermore, the agent was not always detected via ZN staining, which verifies the necessity of ancillary tests. Among these methods IHC has revealed significant sensitivity compared to those of PCRbc and ICCbc (Mc nemar; p<0.05 ve 0.01 respectively), and exhibited compatibility with HE and ZN (Cohen kappa; p<0.001 and 0.05 respectively). These results confirm the fact that rather than one single golden technique, combination of various techniques is necessary for accurate and rapid diagnosis of bovine tuberculosis. It has also been concluded that further investigation is necessary to clarify the efficient routine usage of molecular techniques (PCRtissue/bc) in place of other diagnostic techniques.