High Efficacy of High-dose Nitric Oxide and its Synergistic Effect with Antibiotics against Mycobacterium Abscessus

Mycobacterium abscessus (M. abscessus) is an emerging multi-drug resistant non-tuberculous mycobacterium (NTM) with increasing prevalence in patients with underlying lung disease. We have demonstrated that high-dose nitric oxide (NO) shows potent antibacterial activity against M. abscessus in vitro. Arikayce® (amikacin liposome inhalation) was recently approved by FDA for the treatment of refractory Mycobacterium avium complex lung infection. Clofazimine, used in treatment of leprosy and tuberculosis, has been increasingly utilized in the treatment of M. abscessus lung infection. In this study, we investigated the synergistic effect of high-dose NO combined with amikacin and clofazimine against M. abscessus. We have used a NO Exposure Chamber to test the susceptibility of three M. abscessus clinical strains (MAB-062600, MAB-030804, and MAB-010708) and ATCC 19977 to NO and its combination with clofazimine and amikacin. Disc Diffusion or E-test methods was used to determine the minimum inhibitory concentrations (MICs) for each strain followed by Agar Dilution method to determine synergistic effects. Treatment with 250ppm NO alone for 10hr demonstrated a 5- to 6-log reductions in M. abscessus clinical strains and ATCC 19977. Preliminary results indicate that NO in combination with clofazimine (2X MIC) results in an additional 1-log reduction in MAB-062600 strain compared to NO and CLO alone. Tests on the effects of clofazimine and amikacin in combination with 250ppm NO in remaining M. abscessus strains are ongoing. Our findings suggests that 250ppm NO is highly efficacious against M. abscessus and combination with clofazimine may further improve its activity.