An immunocompetent rat model of Mycobacterium abscessus multinodular granulomatous lung infection

Animal models that can mimic progressive granulomatous pulmonary disease (PD) due to non-tuberculous mycobacteria (NTM) have not been established in rats to date. These models could assist with the study of the pathophysiology of NTM-PD as well as the preclinical development of new therapies. In the present study, an immunocompetent rat model of progressive Mycobacterium abscessus (MABs)- PD was developed using MABs originating from a patient with cystic fibrosis. MABs was embedded in agarose beads and delivered intratracheally to the lungs of Sprague Dawley rats two times at a one-week time interval. The bacterial burden of lysed lungs, spleen and liver was assessed by calculating colony forming units (CFUs) on day 28. Lung CFUs indicated a ∼1.2-2 log₁₀ total CFU increase compared to the initial total bacterial load instilled into the lungs. In all infected rats, multinodular granulomatous inflammatory lesions containing MABs were found in the lung. These findings support the establishment of an immunocompetent MABs PD rat model, characterised by an increase in mycobacterial burden over time and a chronic granulomatous inflammatory response to the MABs infection.