Proton Motive Force-Disrupting Antimycobacterial Guanylurea Polymer.

Mycobacterial infectious diseases, including tuberculosis (TB), severely threaten global public health. Nonreplicating Mycobacterium tuberculosis (Mtb) is extremely difficult to eradicate using current TB drugs that primarily act on replicating cells. Novel TB drugs acting on unconventional targets are needed to combat TB efficiently. Although membrane-disrupting antimicrobial peptides and their synthetic mimics exhibit the potential to kill persisters, the lack of microbe selectivity, especially toward mycobacteria, has been a concern. Here, we report that the recently developed poly(guanylurea)-piperazine (PGU-P) shows fast and selective mycobactericidal effects. Using a nonpathogenic model organism, Mycobacterium smegmatis (Msm), we have found that the mycobactericidal effects of PGU-P are correlated to the disruption of the mycobacterial membrane potential and bioenergetics. Accordingly, PGU-P also potentiates bedaquiline, an oxidative phosphorylation-targeting TB drug disturbing mycobacterial bioenergetics. Importantly, PGU-P also exhibits a promising activity against pathogenic Mtb with a minimum inhibitory concentration of 37 µg/mL. Our results support that PGU-P is a novel class of antimycobacterial biomaterial, and the unique structural feature can contribute to developing novel antimycobacterial drugs.

Chemical Profile and Antimicrobial Activity of the Marine Diatom Chaetoceros muelleri.

Microalgae, due to its rapid growth, low nutritional requirements, and versatility of adaptation to different environmental conditions, has aroused the biotechnological interest, synthesizing novel molecules with antioxidant, anticoagulant, anti-inflammatory, antitumor, and antimicrobial activities. In this sense, we carried out the bioprospection of Chaetoceros muelleri, a marine diatom employed in aquaculture, as a candidate to the development of new drugs for the treatment of bacterial infections. The chemical profile of extracts in different solvents (hexane, chloroform, methylene chloride, ethyl acetate, methanol, and acetone) were analyzed by 1 H-NMR. The hexane extract was the most active against all bacteria species tested, including Mycobacterium tuberculosis, with a minimum inhibitory concentration of 100 µg/ml. Contrarily, the methanol extract was inactive against all tested microorganisms and, in addition, was the only one with IC50 >800 µg/mL, showing no cytotoxicity in VERO cell lines. All other extracts showed antibacterial potential and IC50 values varying between 267.58 and 142.47 µg/ml. The fact that C. muelleri is a microalga easily grown on bioreactors on a large scale may promote its biotechnological use, especially as scaffolds for the development of new compounds against bacterial species of clinical and public health interest.

Whole-genome sequencing as a tool for studying the microevolution of drug-resistant serial Mycobacterium tuberculosis isolates.

Treatment of drug-resistant tuberculosis requires extended use of more toxic and less effective drugs and may result in retreatment cases due to failure, abandonment or disease recurrence. It is therefore important to understand the evolutionary process of drug resistance in Mycobacterium tuberculosis. We here in describe the microevolution of drug resistance in serial isolates from six previously treated patients. Drug resistance was initially investigated through phenotypic methods, followed by genotypic approaches. The use of whole-genome sequencing allowed the identification of mutations in the katG, rpsL and rpoB genes associated with drug resistance, including the detection of rare mutations in katG and mixed populations of strains. Molecular docking simulation studies of the impact of observed mutations on isoniazid binding were also performed. Whole-genome sequencing detected 266 single nucleotide polymorphisms between two isolates obtained from one patient, suggesting a case of exogenous reinfection. In conclusion, sequencing technologies can detect rare mutations related to drug resistance, identify subpopulations of resistant strains, and identify diverse populations of strains due to exogenous reinfection, thus improving tuberculosis control by guiding early implementation of appropriate clinical and therapeutic interventions.