In Vitro Efficacy of Free and Nanoparticle Formulations of Gallium(III) meso-Tetraphenylporphyrine against Mycobacterium avium and Mycobacterium abscessus and Gallium Biodistribution in Mice

The nontuberculous mycobacterial (NTM) pathogens, M. avium complex (MAC) and M. abscessus, can result in severe pulmonary infections. Current antibiotics confront significant challenges for treatment of these NTM infections due to emerging multidrug-resistance. Thus, development of new antibiotics targeted against these agents is needed. We examined the inhibitory activities of Ga(NO3)3, GaCl3, gallium meso-tetraphenylporphyrine (GaTP), and gallium nanoparticles (GaNP) against intra- and extracellular M. avium and M. abscessus. GaTP, an analogue of natural heme, inhibited growth of both M. avium and M. abscessus with MICs in Fe-free 7H9 media of 0.5 and 2 μg/mL, respectively. GaTP was more active than Ga(NO3)3 and GaCl3. Ga(NO3)3 and GaCl3 were not as active in Fe-rich media compared to Fe-free media. However, GaTP was much less impacted by exogenous Fe, with MICs against M. avium and M. abscessus of 2 and 4 μg/mL, respectively, in 7H9 OADC media (Fe rich). Confocal microscopy showed that GaNP penetrates ...