Effects of cigarette smoke on the administration of isoniazid and rifampicin to macrophages infected with Mycobacterium tuberculosis

Sudapyridine (WX-081) antibacterial activity against Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium chelonae in vitro and in vivo

Sudapyridine (WX-081) is a structural analog of bedaquiline (BDQ), which shows anti-tuberculosis and non-tuberculous mycobacteria (NTM) activities but, unlike BDQ, did not prolong QT interval in animal model studies. This study evaluated the antibacterial activity of this novel compound against Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium chelonae in vitro and in vivo. The minimum inhibitory concentration (MIC) of WX-081 against three kinds of non-tuberculous mycobacteria (NTM) clinical strains was determined using microplate-based alamarBlue assay (MABA), and the antibacterial activity of WX-081 against NTM in J774A.1 cells and mice was evaluated. MIC ranges of WX-081 against clinical strains of M. avium and M. abscessus were 0.05-0.94 μg/mL, 0.88-7.22 μg/mL (M. abscessus subsp. abscessus), and 0.22-8.67 μg/mL (M. abscessus subsp. massiliense), respectively, which were slightly higher than those of BDQ. For M. avium, M. abscessus, and M. chelonae, WX-081 can reduce the intracellular bacterial load by 0.13-1.18, 0.18-1.50, and 0.17-1.03 log10 colony forming units (CFU)/mL, respectively, in a concentration-dependent manner. WX-081 has bactericidal activity against three NTM species in mice. WX-081 exhibited anti-NTM activity to the same extent as BDQ both in vivo and in vitro. WX-081 is a promising clinical candidate and should be studied further in clinical trials.

IMPORTANCE

Due to the rapidly increased cases globally, non-tuberculous mycobacteria (NTM) disease has become a significant public health problem. NTM accounted for 11.57% of all mycobacterial isolates in China, with a high detection rate of Mycobacterium abscessus, Mycobacterium avium, and Mycobacterium chelonae during 2000-2019. Treatment of NTM infection is often challenging, as natural resistance to most antibiotics is quite common among different NTM species. Hence, identifying highly active anti-NTM agents is a priority for potent regimen establishment. The pursuit of new drugs to treat multidrug-resistant tuberculosis may also identify some agents with strong activity against NTM. Sudapyridine (WX-081) is a structural analog of bedaquiline (BDQ), which was developed to retain the anti-tuberculosis efficacy but eliminates the severe side effects of BDQ. This study initially evaluated the antimicrobial activity of this novel compound against M. avium, M. abscessus, and M. chelonae in vitro, in macrophages and mice, respectively.

Impact of diesel exhaust particles on infections with Mycobacterium bovis BCG in in vitro human macrophages and an in vivo Galleria mellonella model

There are strong suggestions for a link between pulmonary tuberculosis (TB) and air quality. Diesel exhaust is one of the main contributors to pollution and it is reported to be able to modify susceptibility to lung infections. In this study we exposed THP-1 human macrophages and Mycobacterium bovis BCG to diesel exhaust particles (DEPs). High cytotoxicity and activation of apoptosis was found in THP-1 cells at 3 and 6 days, but no effect was found on the growth of M. bovis BCG. Infection of THP-1 cells exposed to a non-cytotoxic DEP concentration showed a limited capacity to engulf latex beads. However, M. bovis BCG infection of macrophages did not result in an increase in the bacterial burden, but it did result in an increase in the bacteria recovered from the extracellular media, suggesting a poor contention of M. bovis BCG. We also observed that DEP exposure limited the production of cytokines. Using the Galleria mellonella model of infection, we observed that larvae exposed to low levels of DEPs were less able to survive after infection with M. bovis BCG and had a higher internal bacterial load after 4 days of infection. Unraveling the links between air pollution and impairment of human antimycobacterial immunity is vital, because pollution is rapidly increasing in areas where TB incidence is extremely high.

MptpB Inhibitor Improves the Action of Antibiotics against Mycobacterium tuberculosis and Nontuberculous Mycobacterium avium Infections

Treatment of Mycobacterium tuberculosis and Mycobacterium avium infections requires multiple drugs for long time periods. Mycobacterium protein-tyrosine-phosphatase B (MptpB) is a key M. tuberculosis virulence factor that subverts host antimicrobial activity to promote intracellular survival. Inhibition of MptpB reduces the infection burden in vivo and offers new opportunities to improve current treatments. Here, we demonstrate that M. avium produces an MptpB orthologue and that the MptpB inhibitor C13 reduces the M. avium infection burden in macrophages. Combining C13 with the antibiotics rifampicin or bedaquiline showed an additive effect, reducing intracellular infection of both M. tuberculosis and M. avium by 50%, compared to monotreatment with antibiotics alone. This additive effect was not observed with pretomanid. Combining C13 with the minor groove-binding compounds S-MGB-362 and S-MGB-363 also reduced the M. tuberculosis intracellular burden. Similar additive effects of C13 and antibiotics were confirmed in vivo using Galleria mellonella infections. We demonstrate that the reduced mycobacterial burden in macrophages observed with C13 treatments is due to the increased trafficking to lysosomes.