Table 2.

In vitro studies of neutrophil ability for killing or restricting the growth of NTM

Organism	Host	Neutrophil purification	Experimental Read out	Observation	Killing / Restriction	Study reference
M. avium	Human (HIV)	Ficoll gradient 98–99% purity confirmed by microscopy	Radiometric assay (Bactec)	Isolated neutrophils from AIDS patients responded to exogenously supplied G-CSF by inhibiting the growth of mycobacteria	R 3–10 days	[53]
M. avium	Human	Ficoll sedimentation Purity NR	CFU	Half of the bacteria phagocytosed at 15 min were killed by neutrophils at 45 min, and killing was nearly complete at 120 min	K 2 h	[54]
M. avium	Mouse	Ficoll gradient > 97% purity confirmed by microscopy	CFU	Neutrophils from mice treated with G-CSF were able to kill M. avium ex vivo, compared with controls	K 4 h	[40]
M. fortuitum	Human	Ficoll gradient Purity NR	CFU	Killing of mycobacteria in the presence of serum, however no killing occurred in the absence of serum	K 2 h	[55]
M. smegmatis	Human	Percoll, > 99% purity confirmed by haematoxylin staining	CFU	Neutrophils’ antibacterial capacities demonstrated with efficient killing of mycobacteria	K Up to 6 h	[56]
M. abscessus	Human	Percoll, > 98% purity confirmed by microscopy	CFU	Mycobacteria activated the neutrophils’ bacterial clearance mechanisms, including ROS generation, NET formation, and phagocytosis	K 1 h	[57]

K Killing (reduction of CFU number), NR Not recorded, R Restriction (slower increase of CFU)