Multi-Etiological Nature of Tuberculosis-Like Lesions in Condemned Pigs at the Slaughterhouse

Tuberculosis-like lesions (TBL) in pigs have been associated with microorganisms other than mycobacteria. In this work a histopathological and microbiological evaluation of TBL in pigs is shown. A total of 352 samples belonging to 171 pigs totally condemned at slaughterhouse due to generalized TBL were sampled and selected for analysis. Pyogranulomatous (56.2%) and granulomatous lesions (20.2%) were observed in all analysed organs. Most of the granulomas observed in both lymph nodes and lungs belonged to more advanced stages of development (stages III and IV) whereas in the liver and the spleen most of lesions belonged to intermediate stages (stages II and III). Different microorganisms were simultaneously detected from TBL in the 42.7% of the animals. Mycobacterium tuberculosis complex (MTC) (38%), coryneform bacteria (40.3%) and streptococci (28.1%) were the main groups of microorganisms detected after bacteriological analysis, with Trueperella pyogenes and Streptococcus suis as the most frequently isolated species. Mycobacteria belonging to MTC were the most frequently detected pathogens in granulomatous and pyogranulomatous lesions in submandibular lymph nodes (32.7%) and coryneform bacteria were the microorganisms more frequently isolated from lungs (25.9%) and spleen samples (37.2%). These results may provide new insights into the pathogenesis and diagnosis of this pathology. The importance of coryneform bacteria and streptococci in such processes must be evaluated in future studie

Distribution of granulomas per examined organ and stage of development.

<p>^aSLN: submandibular lymph nodes.</p><p>Distribution of granulomas per examined organ and stage of development.</p

Microorganisms isolated from lesions.

<p>^<b>a</b><i>Rhodococcus boritolerans</i>, <i>Dietzia timorensis</i>, <i>Pseudoclavibacter</i> spp, <i>Brevibacterium</i> spp and <i>Actinomyces masicol</i> (1 isolate/each)</p><p>^b<i>Streptococcus</i> spp. (3 isolates), <i>S</i>. <i>mitis</i>, <i>S</i>. <i>rattus</i> and <i>S</i>. <i>bovis</i> (1 isolate/each)</p><p>^c<i>E</i>. <i>faecium</i> (8 isolates) <i>E</i>. <i>durans</i> (3 isolates), <i>E</i>. <i>faecalis</i> (6 isolates), <i>E</i>. <i>gallinarum</i> and <i>E</i>. <i>avium</i> (1 isolate/each)</p><p>^d<i>C</i>. <i>maltaromaticum</i> (16 isolates) and <i>C</i>. <i>divergens</i> (1 isolate)</p><p>^e<i>A</i>. <i>urinae</i> (7 isolates), <i>A</i>. <i>viridans</i> (4 isolates) and <i>A nurinaequi</i> (2 isolates)</p><p>^f<i>S</i>. <i>sciuri</i>, <i>S</i>. <i>xylosus</i> (2 isolates/each), <i>Staphylococcus</i> spp., <i>S</i>. <i>aureus</i> and <i>S</i>. <i>haemolyticus</i> (1 isolate/each)</p><p>^<b>g</b><i>Leuconostoc</i> spp. (4 isolates), <i>Escherichia coli</i> (2 isolates) <i>Mezorhizobium</i> spp., <i>Halospirulina</i> spp., <i>Glanulicatella</i> spp. and <i>Lactococcus lactis</i> (1 isolate/each)</p><p>Microorganisms isolated from lesions.</p

A-G.

<p><b>A)</b> TBL in the submandibular lymph node of an affected pig. Bar, 1cm. B) TBL in the spleen of an affected pig. Bar, 1cm. C) Microscopic image of a TBL lesions in the lymph node of an affected animal showing a profuse infiltrate of degenerated neutrophils. HE. Bar, 200μm. D) Clustered epithelioid macrophages surrounded by lymphocytes and erythrocytes in a stage I granuloma in the liver. HE. Bar, 50μm. E) Coalescent stage II granulomas in the lymph node of a pig showing epithelioid macrophages completely enclosed by a thin capsule, with peripheral infiltration of scattered lymphocytes. HE. Bar, 100μm. F) Stage III granuloma with a central necrotic core, partially mineralized, surrounded by a dense connective tissue capsule infiltrated by lymphocytes and scattered neutrophils. HE. Bar, 100μm. G) Thickly encapsulated, large, irregular, multicentric granulomas with prominent caseous necrosis and multifocal islands of mineralization (stage IV granulomas). HE. Bar, 500μm.</p

Frequency of detected microorganisms and type of lesions identified at individual level.

<p>^aGranulomatous and pyogranulomatous lesions detected in the same animal</p><p>^bNecrotic or calcified foci (5/15) and other lesions or no lesions (10/15)</p><p>Frequency of detected microorganisms and type of lesions identified at individual level.</p

Frequency of detection of microorganisms from TBL within the examined organs.

<p>^aSLN: submandibular lymph nodes.</p><p>Frequency of detection of microorganisms from TBL within the examined organs.</p

Type of lesions identified from samples.

<p>^aSLN: submandibular lymph nodes.</p><p>Type of lesions identified from samples.</p