Mycobacterial Infections in Wild Boars (Sus scrofa) from Southern Switzerland: Diagnostic Improvements, Epidemiological Situation and Zoonotic Potential

Abstract

The occurrence of mycobacterial infections in different hosts and their implication as obligate or opportunistic pathogens remain mainly unclear. In addition to the well-known pathogenic members of the Mycobacterium tuberculosis -complex (MTBC), over 180 nontuberculous mycobacteria (NTM) species have been described. Although the large majority of the NTM are assumed to be non-pathogenic to most individuals, an increasing trend in NTM infections has been observed over the last decades. The reasons of such augmentation are probably more than one: improved laboratory diagnostics, an increasing number of immunocompromised patients and individuals with lung damage are some of the possible aspects. Mandibular lymph nodes of 176 hunted wild boars from the pre-Alpine region of Canton Ticino, Switzerland, were collected. Following gross inspection, each lymph node was subjected to culture and to an IS6110 based real-time PCR specific for MTBC members. Histology was performed of a selection of lymph nodes presenting gross visible lesions. Moreover, accuracy of matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry species identification was compared with sequence analysis of a combination of housekeeping genes. Mycobacteria of the MTBC were detected in five out of 176 wild boars (2.8%; CI95% 1.2 -6.5) and were all confirmed to be Mycobacterium microti by molecular methods. In addition, based on the examined lymph nodes, NTM were detected in 57.4% (CI95% 50.0 -64.5) of the wild boars originating from the study area. The 111 isolates belonged to 24 known species and three potentially undescribed Mycobacterium species. M. avium subsp. hominissuis thereby predominated (22.5%) and was found in lymph nodes with and without macroscopic changes. Overall, the present findings show that, with the exception of undescribed Mycobacterium species where identification was not possible (3.6%; 4/111), MALDI-TOF had a high concordance rate (90.1%; 100/111 isolates) to the sequence based reference method.

Unique genomic sequences in a novelMycobacterium aviumsubsp.hominissuislineage enable fine scale transmission route tracing during pig movement

“…Based on this observation, it is unlikely that new MAH lineage was introduced from these regions. It is reported that MAH is isolated from wild boars in Europe (39), however, MAH is not isolated from wild animals in the same area of this study (40). Epidemiological information from farms harboring infected pigs revealed that the source of the new MAH lineage was likely introduced by pig movement.…”

Highly resistant Mycobacterium abscessus subsp. abscessus infection in a Swiss cat

“…The specimen was decontaminated and processed as described before. 11,12 Direct Ziehl-Neelsen staining of the decontaminated material revealed acid-fast bacilli (Figure 3). Three days after inoculation of liquid mycobacterial media (BBL MGIT, Becton Dickinson, Switzerland) supplemented with PANTA (polymyxin B, amphotericin B, nalidixic acid, trimethoprim, azlocillin) antibiotic mixture, and incubation at 30 • C, growth was detected.…”

“…A swab sample from the purulent skin lesion was submitted for mycobacterial culture. The specimen was decontaminated and processed as described before 11,12 . Direct Ziehl‐Neelsen staining of the decontaminated material revealed acid‐fast bacilli (Figure 3).…”

“…Subcultures on solid media (Middlebrook 7H10) showed rough, whitish colonies. Species identification was performed using MALDI‐TOF MS mass spectrometry 12 and revealed the presence of Mycobacterium abscessus . Sequencing of the rpoB gene 13 allowed further characterization at subspecies level, and the isolate was identified as Mycobacterium abscessus subsp.…”

“…Subcultures on solid media (Middlebrook 7H10) showed rough, whitish colonies. Species identification was performed using MALDI-TOF MS mass spectrometry 12 ing of the rpoB gene 13 allowed further characterization at subspecies level, and the isolate was identified as Mycobacterium abscessus subsp. abscessus with an identity score of 99% (728/729) compared with Mycobacterium abscessus subsp.…”