Comparative Evaluation of theIn VitroAntimycobacterial Activities of Six Aminoglycoside Antibiotics Using an Agar Dilution Method

Recognizing drug targets using evolutionary information: implications for repurposing FDA-approved drugs against Mycobacterium tuberculosis H37Rv

Drug repurposing to explore target space has been gaining pace over the past decade with the upsurge in the use of systematic approaches for computational drug discovery. Such a cost and time-saving approach gains immense importance for pathogens of special interest, such as Mycobacterium tuberculosis H37Rv. We report a comprehensive approach to repurpose drugs, based on the exploration of evolutionary relationships inferred from the comparative sequence and structural analyses between targets of FDA-approved drugs and the proteins of M. tuberculosis. This approach has facilitated the identification of several polypharmacological drugs that could potentially target unexploited M. tuberculosis proteins. A total of 130 FDA-approved drugs, originally intended against other diseases, could be repurposed against 78 potential targets in M. tuberculosis. Additionally, we have also made an attempt to augment the chemical space by recognizing compounds structurally similar to FDA-approved drugs. For three of the attractive cases we have investigated the probable binding modes of the drugs in their corresponding M. tuberculosis targets by means of structural modelling. Such prospective targets and small molecules could be prioritized for experimental endeavours, and could significantly influence drug-discovery and drug-development programmes for tuberculosis.

Active pulmonary tuberculosis: Role for amikacin in early treatment

OBJECTIVE

To evaluate the efficacy of amikacin on sputum conversion during initial sputum smear positive tuberculosis treatment.

MATERIAL AND METHODS

Single-center observational cohort study (2012-2013) evaluating time to sputum smear conversion with standard treatment (ST) versus standard treatment+amikacin (IV 15mg/kg/day) for seven days (STamK).

RESULTS

Forty-five patients were included. Median time to smear negative samples was 26.5 days (14-56) for the 30 (66.7%) patients included in the ST group and 48 days (19.5-69.5) for the 15 patients (33.3%) included in the STamK group (P=0.76). Time to negative culture was only known for 27 patients (61.4%): 47.5 days (26-58) for 18 patients in the ST group and 40 days (14-77) for nine patients in the STamK group.

CONCLUSION

Despite our small sample size, the addition of amikacin in active tuberculosis treatment did not seem to impact time to smear conversion or period of contagiousness.

Adaptation of mycobacteria on solid, egg-based media to anaerobic conditions and characterization of their diagnostic phenotypes

Recent evidence indicates that human pulmonary tuberculous granulomas are hypoxic, and a related dormancy model has been established for Mycobacterium tuberculosis using liquid media in tightly sealed tubes. In the present study, we examined the growth capacity of various mycobacterial species on solid, egg-based media under oxygen-limited conditions. During primary anaerobic cultivation on an Ogawa egg-based medium, all of the inoculated mycobacterial strains persisted for 10 weeks without detectable colony formation on the surface of the medium. Because these anaerobic cultures were restored and possessed the capacity to grow within 3 weeks following transfer to microaerobic conditions (5% or 10% oxygen tension), it was evident that the organisms persisted in a non-replicative dormant state as seen with anaerobic cultures in liquid media. The colonies grown under microaerobic conditions were also capable of growth under anaerobic conditions. Anaerobic growth could be observed only when the microaerobically grown colonies were subcultured under anaerobic conditions, suggesting that preliminary adaptation to the environment under reduced oxygen tensions is an essential process to enable growth under anaerobic conditions. A similar mode of anaerobic growth on slants of an egg-based medium was also observed with clinical isolates of M. tuberculosis. All of the clones that were adapted to grow in the anaerobic environments retained their species-specific colonial morphologic features, while, among the biochemical characteristics tested, heat-stable catalase activity and niacin accumulation in the medium disappeared during adaptation to anaerobic growth. Based on these results, we conclude that egg-based media actively support the anaerobiosis of mycobacteria exhibiting either a non-replicative dormant state or anaerobic growth, both of which are associated with latency and reactivation of tuberculosis. It was also evident that the use of egg-based media would be of great advantage in the diagnostic characterization of the reactivated clones of mycobacteria.