Trend analysis suggested a change in subspecies among Mycobacterium avium isolated from pigs in Belgium, 1967–2013

Mycobacterium avium is one of the most frequently isolated non-tuberculous mycobacteria, responsible of human and porcine infections. The species M avium consists of four subspecies; M avium subspecies avium (MAA), M avium subspecies silvaticum (MAS), M avium subspecies paratuberculosis (MAP) and M avium subspecies hominissuis (MAH) (Thorel and others 1990, Mijs a nd others 2002, Turenne and others 2007). Given its pathogenicity for both human beings and pigs, MAH represents an increasing public health concern (Pate and others 2011, Iwamoto and others 2012, Muwonge and others 2014). In pigs, these mycobacteria provoke granulomatous lesions mainly in lymph nodes of the digestive tract, potentially reducing the value of carcases (Alvarez and others 2011).Recently, the authors reported on the predominance of MAH among Belgian patients (98.9 per cent) and slaughter pigs (100 per cent) infected by M avium (Vluggen and others 2016). Genotyping of these isolates revealed a large genetic diversity and the absence of a link between genotypes and the place of residence (human) or the farm of origin (pigs) suggesting an environmental source of infection (Vluggen and others 2016).As porcine M avium isolates collected in Belgium during an earlier period of time (1967–1968 and 1992–1996) were available in the Belgian Co-ordinated collections of micro-organisms (BCCM)/Institute of Tropical Medicine (ITM) collection, the authors performed subspecies determination and genotyping on this panel in order to compare the results with those from the more recent isolates sampled in 2012–2013 (Vluggen and others 2016), to investigate the evolution of M avium subspecies distribution over time in infected domestic pigs.All 37 …