Postmortem Evaluation of Tuberculous Lesions

Experimental animals were euthanized at 9 weeks post-challenge with an overdose of intravenous sodium pentobarbital (two goats from the control group were humanely euthanized at week 7). At necropsy, the diameter of TB compatible lesions in retropharyngeal (right and left), mediastinal (cranial and caudal) and tracheobronchial lymph nodes (LN) were measured, and the volume of lesions was inferred as previously described^{31 (link)}. Other visible lesions in extrapulmonary tissues were also recorded and fixed in 10%-buffered formalin to be confirmed by histopathology and the Ziehl Neelsen stain to detect acid-fast bacilli. Lungs were also formalin-fixed, including airways perfusion with formalin before immersion, as previously described^{2 (link)}, and then scanned by computed tomography (CT) using a 16-slice multi-detector scanner (Brivo CT-385, General Electric Healthcare, Madrid, Spain). CT analysis was performed as previously described^{31 (link)}. Briefly, total volumes of lungs and TB lesions were measured using volume rendering images with different density patterns (i.e. solid, mineralized and cavitary lesions), and total volume of mineralization was calculated using 100–300 Hounsfield units.