Experimental infection and bacterial quantification

Infection with M. avium strain 2447 (provided by Dr. Françoise Portaels, Institute of Tropical Medicine, Antwerp, Belgium) was performed intravenously through the lateral tail vein, delivering 10⁶ colony forming units (CFU) per mouse, in a 200 μL volume of sterile saline with 0.05% of Tween80. At selected time-points post-infection, mice were euthanized by carbon dioxide inhalation; organs were aseptically removed and individually homogenized in sterile water with 0.05% of Tween80. Ten-fold serial dilutions of organ homogenates were plated onto OADC-supplemented Middlebrook 7H10 agar plates (Becton Dickinson, NJ, USA) and incubated at 37 °C for 7 days before bacterial burden determination.