title: A comparative study of Mycobacterium avium subsp. avium and Mycobacterium avium subsp. hominissuis in experimentally infected pigs.
abstract: BACKGROUND
  Mycobacterium avium subsp. avium (Maa) and Mycobacterium avium subsp. hominissuis (Mah) are opportunistic pathogens that may infect several species, including humans and pigs. Mah is however more frequently isolated from pigs than Maa, and it is unclear if this is due to difference in virulence or in exposure to the two organisms. Clinical isolates of each subspecies were administered perorally to ten domestic pigs, respectively. The animals were sacrificed at six and 12 weeks after inoculation. At necropsy, macroscopic lesions were recorded, and tissue samples were collected for mycobacterial culture, IS1245 real time PCR and histopathological examination. Culturing was also performed on faecal samples collected at necropsy.
  
  
  RESULTS
  Macroscopic and histopathological lesions were detected in pigs infected with each subspecies, and bacterial growth and histopathological changes were demonstrated, also in samples from organs without gross pathological lesions. Six weeks after inoculation, live Mah was detected in faeces, as opposed to Maa. The presence of live mycobacteria was also more pronounced in Mah infected tonsils. In comparison, the Maa isolate appeared to have a higher ability of intracellular replication in porcine macrophages compared to the Mah isolate.
  
  
  CONCLUSIONS
  The study shows that both subspecies were able to infect pigs. Additionally, the more extensive shedding of Mah might cause pig-to-pig transmission and contribute to the higher incidence of infection caused by this subspecies.
authors.affiliation: Norwegian Veterinary Institute, PO Box 750 Sentrum, N-0106 Oslo, Norway. angelika.agdestein@vetinst.no
authors.forename: Angelika
authors.initials: A
authors.lastname: Agdestein
authors.forename: Tone B
authors.initials: TB
authors.lastname: Johansen
authors.forename: Øyvor
authors.initials: Ø
authors.lastname: Kolbjørnsen
authors.forename: Anne
authors.initials: A
authors.lastname: Jørgensen
authors.forename: Berit
authors.initials: B
authors.lastname: Djønne
authors.forename: Ingrid
authors.initials: I
authors.lastname: Olsen
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D007963:Leukocytes, Mononuclear / Q000382:microbiology; D009162:Mycobacterium avium / Q000145:classification*; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000473:pathology; D014376:Tuberculosis / Q000382:microbiology / Q000662:veterinary*