Location: Infectious Bacterial Diseases ResearchTitle: Evaluation of tissue fixation methods to inactivate Mycobacterium bovis under routine laboratory conditions
Submitted to: Applied Biosafety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2017
Publication Date: 11/8/2017
Citation: Thacker, T.C., Palmer, M.V., Waters, W.R. 2017. Evaluation of tissue fixation methods to inactivate Mycobacterium bovis under routine laboratory conditions. Applied Biosafety. 22(4):152-155. https://doi.org/10.1177%2F1535676017737315.
Interpretive Summary: Mycobacterium bovis (M. bovis) causes tuberculosis in animals and humans. M. bovis is handled under biosafety level-3 conditions. Historical scientific literature report killing and failure to kill Mycobacterium tuberculosis and other mycobacteria by formalin (and similar agents such as embalming fluid). Comparing these studies is difficult because the researchers used different solutions that contained different concentrations of formalin, different inactivation/fixation times, and tissues. Here we report that a 10% neutral buffered formalin solution will kill M. bovis in tissues from infected animals; however, zinc based fixative will not.
Technical Abstract: Mycobacterium bovis (M. bovis) is the etiological agent of tuberculosis in mammals including humans. The seriousness of disease and low infective dose require that the agent be handled under biosafety level 3 conditions. Many experimental protocols include histological examination of infected tissues which are often performed in biosafety level 2/1 laboratories; thus, requiring inactivation of M. bovis within the tissues, preferably during tissue fixation. Fixation with a 10% neutral buffered formalin (3.7% formaldehyde) solution for 24 hours inactivated M. bovis in situ. In contrast Zinc fixative did not inactivate M. bovis in situ. Fixation with 10% neutral buffered formalin rendered tissues safe to transition to biosafety level 2/1 laboratories for histopathological examination.