Macroscopic and Histological Examination
After removal of fat and connective tissue, qualified staff inspected
the lymph nodes macroscopically and recorded pathological changes. A
subset of samples was additionally submitted for histology. Selection
criteria were focusing on infections with the seven most prevalentMycobacterium species and presenting macroscopic lesions. In
addition, all lymph nodes that tested positive for MTBC by real-time PCR
were submitted for histological examination. Samples were fixed in 10%
buffered formalin and embedded in paraffin. Two to three-micron-thick
tissue sections were obtained and stained with hematoxylin and eosin
(HE). Additionally, in cases where lesions consistent with mycobacterial
infections were observed after HE staining, an additional ZN staining
was performed.
Geographical Distribution and Statistical Analysis. The
geographical distribution of the lymph nodes showing growth of
mycobacteria and the circulation of the different NTM on the territory
were investigated using the free software QGIS Desktop 3.6.1. Based on
the collected data regarding sex and age of the animals, statistical
analysis was performed using GraphPad Prism 8.2.1 (GraphPad Software,
San Diego, USA). Fisher’s exact test was used to evaluate different age
groups and the presence of viable NTM isolated from their lymph nodes.
Moreover a possible association between the isolation of Mah , the
most prevalent isolated species, and the three age groups was
investigated with the same test. Statistical significance was set toP -value < 0.05.