Abstract
Mycobacterium avium represents a health concern for both humans and pigs. The characterisation of its subspecies is an important step improving the understanding of the epidemiology and the control of this pathogen. Ninety-two human M. avium strains were selected for a retrospective study. Subspecies determination by rpoB sequencing and IS1245/IS901 analysis showed that 98.9% of Belgian human M. avium strains belong to the subspecies hominissuis (MAH). Some of these MAH strains present particular IS1245/IS901 profiles (absence of IS1245 and false IS901 detection provoked by the presence of ISMav6). In addition, 54 MAH strains isolated from submandibular lymph nodes of Belgian pigs with lymphadenitis were included in this study. Genotyping of human and porcine isolates was performed using multispacer sequence typing (MST). In total, 49 different MST types were identified among pig (n = 11) and human (n = 43) MA isolates, with only five shared by both hosts. Among these MST types, 34 were newly identified. Our findings demonstrate the extensive genetic diversity among MAH isolates. Some genotypes were more prevalent in human or pigs but no correlation was observed between MST type and place of residence or the farm of origin for human and porcine isolates respectively, suggesting an environmental source of infection.
Highlights
Among non-tuberculous mycobacteria (NTM), Mycobacterium avium complex (MAC), composed of two major species M. avium and M. intracellulare, is the most frequently isolated from patients [1,2] and the most common NTM identified as responsible of pulmonary disease [3]
M. avium subsp. hominissuis (MAH) can infect a wide variety of animals, pigs are its primary animal host species, causing granulomatous lesions mainly in the lymph nodes of the digestive tract, which can reduce the value of carcasses [12]
The vast majority of these were isolated from the respiratory tract (n = 51; 95% confidence interval (CI): 59.9–81.9) followed by lymph nodes (n = 13; 95% CI: 10.1–29.3), abscesses (n = 4; 95% CI: 1.6–13.8), blood (n = 2; 95% CI: 0.3–9.8) and peritoneal fluid (n = 1; 95% CI: 0.04–7.6)
Summary
Among non-tuberculous mycobacteria (NTM), Mycobacterium avium complex (MAC), composed of two major species M. avium and M. intracellulare, is the most frequently isolated from patients [1,2] and the most common NTM identified as responsible of pulmonary disease [3]. A phylogenetic study showed that MAH represents diverse groups of organisms from which two distinct groups, MAP and MAA/MAS, have evolved independently [8]. These subspecies of M. avium are genetically close, yet differ widely in their host range and pathogenicity. MAA and MAS mainly infect birds causing a tuberculosis-like disease, whereas MAH is a frequent agent of human and pig mycobacterioses [6,11]. MAH can infect a wide variety of animals, pigs are its primary animal host species, causing granulomatous lesions mainly in the lymph nodes of the digestive tract, which can reduce the value of carcasses [12].
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