A smooth tubercle bacillus from Ethiopia phylogenetically close to the Mycobacterium tuberculosis complex

Draft genome sequences of clinical Mycobacterium canettii strains in Canada

Mycobacterium canettii is a rare pathogen causing tuberculosis in humans and presents a risk to public health. Here, we report the genome sequences of two M. canettii strains. The genomes will assist in creating sequence-based tools for M. canettii and serve as references for identification, surveillance, and epidemiological investigations.

Evaluating the efficacy of whole genome sequencing in predicting susceptibility profiles for first-line antituberculosis drugs

OBJECTIVES

This study aimed to examine the efficacy of whole genome sequencing (WGS) in accurately predicting susceptibility profiles, potentially eliminating the need for conventional phenotypic drug susceptibility testing (pDST) for first-line antituberculosis drugs in routine tuberculosis diagnosis.

METHODS

Over the period of 2017 to 2020, 1114 Mycobacterium tuberculosis complex isolates were collected with drug susceptibility testing conducted using the MGIT960 system and WGS performed for predicting drug resistance profiles. In addition, we implemented a new algorithm with an updated WGS workflow, omitting pan-susceptible strains from pDST.

RESULTS

Results showed that out of 1075 analysed isolates, WGS-based genotypic sensitivity predictions for isoniazid, rifampicin, ethambutol, and pyrazinamide were 100% (95% CI, 99.6-100%), 100% (95% CI, 99.62-100%), 99.8% (95% CI, 99.26-99.94%), and 100% (95% CI, 99.63-100%), respectively. In contrast, the WGS-based genotypic resistance prediction, was 98.85% (95% CI, 93.77-99.79%) for isoniazid, 94.74% (95% CI, 82.71-98.54%) for rifampicin, 86.96% (95% CI, 67.87-95.46%) for ethambutol, and 75.7% (95% CI, 59.9-86.63%) for pyrazinamide. Moreover, WGS enabled the implementation of a new testing algorithm that made it unnecessary to perform pDST in 954 of all 1075 samples (88.7%) and in 890 of 901 pan-susceptible samples (98.8%).

DISCUSSION

Integrating WGS into tuberculosis management offers significant potential to replace phenotypic drug susceptibility testing, especially for problematic drugs like pyrazinamide and ethambutol, potentially improving treatment outcomes.

Evolution and emergence of Mycobacterium tuberculosis

Tuberculosis (TB) remains one of the deadliest infectious diseases in human history, prevailing even in the 21st century. The causative agents of TB are represented by a group of closely related bacteria belonging to the Mycobacterium tuberculosis complex (MTBC), which can be subdivided into several lineages of human- and animal-adapted strains, thought to have shared a last common ancestor emerged by clonal expansion from a pool of recombinogenic Mycobacterium canettii-like tubercle bacilli. A better understanding of how MTBC populations evolved from less virulent mycobacteria may allow for discovering improved TB control strategies and future epidemiologic trends. In this review, we highlight new insights into the evolution of mycobacteria at the genus level, describing different milestones in the evolution of mycobacteria, with a focus on the genomic events that have likely enabled the emergence and the dominance of the MTBC. We also review the recent literature describing the various MTBC lineages and highlight their particularities and differences with a focus on host preferences and geographic distribution. Finally, we discuss on putative mechanisms driving the evolution of tubercle bacilli and mycobacteria in general, by taking the mycobacteria-specific distributive conjugal transfer as an example.