Genome sequence of four strains of Mycobacterium avium ssp hominissuis, isolated in swine and human, differing in virulence in a murine intranasal infection model.. Sequence of four strains of M. avium ssp hominissuis, isolated in swine and human.

Among non-tuberculous mycobacteria (NTM), bacteria of the Mycobacterium avium complex (MAC) are the most frequently isolated from patients. The M. avium species is divided into four subspecies: M. avium ssp. avium (Maa), M. avium ssp. silvaticum (Mas), M. avium ssp. paratuberculosis (Map) and M. avium ssp. hominissuis (Mah). These subspecies of M. avium are genetically very close but they differ widely in their host range and pathogenicity. Indeed, Map is responsible for an intestinal illness in ruminants known as Johne’s disease and could be implicated in human Crohn’s disease. Maa and Mas mainly infect birds causing a tuberculosis-like disease, whereas Mah is a frequent agent of human and pig mycobacterioses and an association between Mah and human lymphadenitis has been described. As Mah represents an increasing public health concern given its pathogenicity for both humans and pigs, detailed genotyping of human clinical isolates and swine isolates should contribute to establish or exclude any epidemiological links between both hosts. Using multispacer sequence typing (MST) we previously identified 46 different genotypes of M. avium ssp. hominissuis isolated among humans and pigs in Belgium, between 2011 and 2013. Using an intranasal infection model in BALB/c mice we compared the virulence of porcine and human isolates with different MST types (Bruffaerts et al, manuscript in preparation). Bacterial replication was monitored for 3 months by plating lung, spleen and liver homogenates on Middlebrook 7H11 agar. Isolates varied significantly in virulence, with a human (12_062) and a porcine (LYM122) isolate of MST type 22 clearly showing higher bacterial numbers in lungs and more dissemination to spleen and liver than a human (12_067) and a porcine (LYM086) isolate of MST type 91.