Introduction

Bovine tuberculosis (bTB) is a chronic disease caused by members of theMycobacterium tuberculosis complex (MTBC) (Rodriguez-Campos et al., 2014). MTBC have been isolated from numerous different domestic and wild animal species. Recent epidemiological investigations have shown the fundamental role played by wildlife in the maintenance of the causal agents of bTB. This results in continuous interspecies transmissions from wild animals to livestock and vice versa, hindering national and international eradication programs (Atkins and Robinson, 2013, Garcia-Jimenez et al., 2016, Maria et al., 2015, Nigsch et al., 2018). Badger (Meles meles ), free–ranging red deer (Cervus elaphus elaphus ) and wild boar (Sus scrofa ) are the most relevant known wild animals acting as a reservoir of bTB in Europe, including Great Britain. The ongoing geographic expansion of wild boar populations have raised concerns regarding the monitoring of several infectious diseases, including zoonotic plagues like bTB and hepatitis E (Gortazar et al., 2008, Martinelli et al., 2015). Beside the members of the MTBC and Mycobacterium leprae, the agent that causes Hansen’s disease, over 180 species of nontuberculous mycobacteria (NTM) have been described (Gupta et al., 2018). NTM are commonly encountered in the environment and they have been isolated from a variety of sources, including water, feed, soil, dust, aerosol, invertebrates, protozoa or animals (Falkinham, 2015, Ghielmetti et al., 2018). Of these, two species are recognized as true pathogens for humans, namely M. marinum and M. ulcerans (Johansen et al., 2020). Nevertheless, more than 60 species of NTM are known to be opportunistic pathogenic to humans and other mammals, and infections with these emerging pathogens are now more common than tuberculosis in industrialized countries (Biet and Boschiroli, 2014, Griffith et al., 2007, Tortoli, 2014). Immunocompromised individuals are highly susceptible to opportunistic NTM infections and improved laboratory diagnostics have enabled more accurate detection of fastidious or extremely slow growing species. Despite the increasing relevance in mycobacterial infections, only restricted information on the occurrence and their diversity in wildlife is available. Moreover, although wild boars are among the most widely distributed large mammals in the world (Oliver et al., 1993), the literature concerning this species is mainly focused on (i) the presence of MTBC and (ii) the impact of NTM infections on the prevalence of MTBC (Boniotti et al., 2014, Chiari et al., 2016, Di Marco et al., 2012, Michelet et al., 2015, Naranjo et al., 2008, Richomme et al., 2010, Santos et al., 2009, Vicente et al., 2006). Canton Ticino is the most southern Canton of Switzerland and a large proportion of his border is shared with Italy. The territory encompasses an area of 2‘812 square kilometre where the majority of the urban area is concentrated in the flat land and forests cover about one third of the alpine region. The wild boar presence in the territory has been documented during the XVI century. Thereafter, it disappeared and it is only since 1981 that it has been officially sighted again (Dipartimento Territorio / Finanze e Economia, 2010). The wild boars are distributed almost exclusively along flat- and hilly land, with the highest animal density observed in the southern districts of Mendrisio, Lugano and the lower part of the Maggia valley (Dipartimento Territorio / Finanze e Economia, 2010). The population increase is estimated at 100%-180%, consequently the population can theoretically double or even triplicate in 12 months without control measurements. In order to regulate this growth, licensed hunters are allowed to hunt the animals each year in September without sex or hunting bag restrictions. Wild boar is one of the most hunted mammalians in the Canton of Ticino, second only to red deer.
Recent studies from Spain, Czech Republic, Brazil and Slovenia comprehensively evaluated the spectrum of NTM species in black pigs using molecular methods (Garcia-Jimenez et al., 2015, Gortazar et al., 2011, Pate et al., 2016, Trcka et al., 2006). It is significant to note that, the latter mentioned publications, describe significant differences in the spectrum of species isolated. Such differences may not be exclusively the result of geographic distribution of NTM, but the advance in molecular techniques and the progress in mycobacterial characterization led to enormous diagnostic improvements over the past decades (Tortoli, 2014). It is noteworthy, that the dissection of the M. avium complex (MAC) in the mentioned publications was performed at different levels, impeding a direct comparison of the isolated mycobacteria. The characterization of NTM from clinical samples is often a challenge for laboratory personal in routine diagnostic. Because of its rapidness, cost-effectiveness and high throughput the matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) technology has nowadays been integrated in the workflow of numerous diagnostic laboratories (Alcaide et al., 2018, Mediavilla-Gradolph et al., 2015, Murugaiyan et al., 2018). However, the accuracy achievable at present with genetic approaches remains superior to the MALDI-TOF-based species identification (Tortoli, 2014). Therefore, the accuracy and limitations of this method based on ordinary samples from veterinary origin should be evaluated. The present research used a panel of NTM showing a wide range of species isolated from a common source and verified the consensus grade between sequence analysis and MALDI-TOF. This study aimed (i) to determine the occurrence and diversity of mycobacterial species among healthy wild boar hunted in Canton Ticino, (ii) to identify the geographical distribution of mycobacterial species, and (iii) to compare two different diagnostic identification approaches for the genus Mycobacterium .