Ready Experimental Translocation of Mycobacterium canettii Yields Pulmonary Tuberculosis

Abstract

<i>Mycobacterium canettii</i>, which has a smooth colony morphology, is the tuberculous organism retaining the most genetic traits from the putative last common ancestor of the rough-morphology <i>Mycobacterium tuberculosis</i> complex. To explore whether <i>M. canettii</i> can infect individuals by the oral route, mice were fed phosphate-buffered saline or 10⁶<i>M. canettii</i> mycobacteria and sacrificed over a 28-day experiment. While no <i>M. canettii</i> was detected in negative controls, <i>M. canettii</i>-infected mice yielded granuloma-like lesions for 4/4 lungs at days 14 and 28 postinoculation (p.i.) and positive PCR detection of <i>M. canettii</i> for 5/8 mesenteric lymph nodes at days 1 and 3 p.i. and 5/6 pooled stools collected from day 1 to day 28 p.i. Smooth <i>M. canettii</i> colonies grew from 68% of lungs and 36% of spleens and cervical lymph nodes but fewer than 20% of axillary lymph nodes, livers, brown fat samples, kidneys, or blood samples throughout the 28-day experiment. Ready translocation in mice after digestive tract challenge demonstrates the potential of ingested <i>M. canettii</i> organisms to relocate to distant organs and lungs. The demonstration of this relocation supports the possibility that populations may be infected by environmental <i>M. canettii</i>.