Replication of Mycobacterium avium subsp. hominissuis (Mah) or Mycobacterium avium subsp. avium (Maa) in porcine macrophages. Intracellular replication in macrophages from four un-inoculated pigs was measured by the number of the single copy housekeeping gene hsp65 copies, as determined by real time PCR analysis of lysates harvested at six hours, one day and seven days after infection. Numbers are presented as the mean of duplicate wells. Control lysates were negative on real time PCR and are not shown.