Deciphering the Proteomic Landscape of Mycobacterium tuberculosis in Response to Acid and Oxidative Stresses

Bigger problems from smaller colonies: emergence of antibiotic-tolerant small colony variants of Mycobacterium avium complex in MAC-pulmonary disease patients

BACKGROUND

Mycobacterium avium complex (MAC) is a group of slow-growing mycobacteria that includes Mycobacterium avium and Mycobacterium intracellulare. MAC pulmonary disease (MAC-PD) poses a threat to immunocompromised individuals and those with structural pulmonary diseases worldwide. The standard treatment regimen for MAC-PD includes a macrolide in combination with rifampicin and ethambutol. However, the treatment failure and disease recurrence rates after successful treatment remain high.

RESULTS

In the present study, we investigated the unique characteristics of small colony variants (SCVs) isolated from patients with MAC-PD. Furthermore, revertant (RVT) phenotype, emerged from the SCVs after prolonged incubation on 7H10 agar. We observed that SCVs exhibited slower growth rates than wild-type (WT) strains but had higher minimum inhibitory concentrations (MICs) against multiple antibiotics. However, some antibiotics showed low MICs for the WT, SCVs, and RVT phenotypes. Additionally, the genotypes were identical among SCVs, WT, and RVT. Based on the MIC data, we conducted time-kill kinetic experiments using various antibiotic combinations. The response to antibiotics varied among the phenotypes, with RVT being the most susceptible, WT showing intermediate susceptibility, and SCVs displaying the lowest susceptibility.

CONCLUSIONS

In conclusion, the emergence of the SCVs phenotype represents a survival strategy adopted by MAC to adapt to hostile environments and persist during infection within the host. Additionally, combining the current drugs in the treatment regimen with additional drugs that promote the conversion of SCVs to RVT may offer a promising strategy to improve the clinical outcomes of patients with refractory MAC-PD.

Revolutionizing Tuberculosis Treatment: Uncovering New Drugs and Breakthrough Inhibitors to Combat Drug-Resistant Mycobacterium tuberculosis

Tuberculosis (TB) is a global health threat that causes significant mortality. This review explores chemotherapeutics that target essential processes in Mycobacterium tuberculosis, such as DNA replication, protein synthesis, cell wall formation, energy metabolism, and proteolysis. We emphasize the need for new drugs to treat drug-resistant strains and shorten the treatment duration. Emerging targets and promising inhibitors were identified by examining the intricate biology of TB. This review provides an overview of recent developments in the search for anti-TB drugs with a focus on newly validated targets and inhibitors. We aimed to contribute to efforts to combat TB and improve therapeutic outcomes.

EphH, a unique epoxide hydrolase encoded by Rv3338 is involved in the survival of Mycobacterium tuberculosis under in vitro stress and vacuolar pH-induced changes

Introduction

Mycobacterium tuberculosis (Mtb), one of the deadliest human pathogen, has evolved with different strategies of survival inside the host, leading to a chronic state of infection. Phagosomally residing Mtb encounters a variety of stresses, including increasing acidic pH. To better understand the host-pathogen interaction, it is imperative to identify the role of various genes involved in the survivability of Mtb during acidic pH environment.

Methods

Bio-informatic and enzymatic analysis were used to identify Mtb gene, Rv3338, as epoxide hydrolase. Subsequently, CRISPRi knockdown strategy was used to decipher its role for Mtb survival during acidic stress, nutrient starvation and inside macrophages. Confocal microscopy was used to analyse its role in subverting phagosomal acidification within macrophage.

Results

The present work describes the characterization of Rv3338 which was previously known to be associated with the aprABC locus induced while encountering acidic stress within the macrophage. Bio-informatic analysis demonstrated its similarity to epoxide hydrolase, which was confirmed by enzymatic assays, thus, renamed EphH. Subsequently, we have deciphered its indispensable role for Mtb in protection from acidic stress by using the CRISPRi knockdown strategy. Our data demonstrated the pH dependent role of EphH for the survival of Mtb during nutrient starvation and in conferring resistance against elevated endogenous ROS levels during stress environment.

Conclusion

To the best of our knowledge, this is the first report of an EH of Mtb as a crucial protein for bacterial fitness inside the host, a phenomenon central to its pathogenesis.