Summary
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 theMycobacterium 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 Mycobacteriumspecies. 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.
Keywords: Mycobacterium microti ; Mycobacterium avium ;
nontuberculous mycobacteria; wild boar; MALDI-TOF MS; rpoB ,hsp65 , 16S rRNA gene.