Detection of differentially culturable tubercle bacteria in sputum from drug-resistant tuberculosis patients

Collaborative learning in the digital age: empowering tuberculosis researchers through virtual training

Integrating whole genome sequencing (WGS) of the Mycobacterium tuberculosis complex into routine care, surveillance, and research in high tuberculosis burden settings remains challenging due to limited resources and skills. While technological platforms for scaling WGS are emerging, scaling wet lab and analytic components often depends on partnerships where such skills have been established. To address this, a virtual training program was developed. Over 12 weeks, 21 trainees from five Southern African institutes engaged in learning from curated theoretical content and interactive virtual meetings with experienced instructors. The training program, developed by a diverse team of experts in molecular biology, biomedical research, microbiology, and tuberculosis research, provided comprehensive coverage aligned with the latest advancements. Teaching strategies included interactive mentor-led sessions and real-time feedback, together with facilitated knowledge exchange and understanding. The virtual training program yielded several successes. Of note, trainees submitted three scientific articles for peer review, based on their acquired knowledge and its application in research. The program also fostered collaborations on Mycobacterium tuberculosis WGS among participants, showcasing the potential for networking and future joint projects. While the virtual training program encountered challenges related to the pandemic, limited resources, trainee engagement, and language barriers, these were creatively mitigated. To improve future training sessions, a platform assessing participant engagement and information retention is recommended. Wider collaborative efforts among experts and institutions in collating resources will lead to more comprehensive training programs. Addressing challenges such as internet connectivity issues and language barriers is crucial for ensuring inclusivity and enhancing the overall learning experience. In conclusion, the virtual training program successfully provided knowledge and skill training in WGS to trainees, leading to scientific article submissions and collaborations. Furthermore, content creators benefited from improved science communication and training opportunities.

Clinical Strains of Mycobacterium tuberculosis Representing Different Genotype Families Exhibit Distinct Propensities to Adopt the Differentially Culturable State

Growing evidence points to the presence of differentially culturable tubercle bacteria (DCTB) in clinical specimens from individuals with active tuberculosis (TB) disease. These bacteria are unable to grow on solid media but can resuscitate in liquid media. Given the epidemiological success of certain clinical genotype families of Mycobacterium tuberculosis, we hypothesize that different strains may have distinct mechanisms of adaptation and tolerance. We used an in vitro carbon starvation model to determine the propensity of strains from lineages 2 and 4 that included the Beijing and LAM families respectively, to generate DCTB. Beijing strains were associated with a greater propensity to produce DCTB compared to LAM strains. Furthermore, LAM strains required culture filtrate (CF) for resuscitation whilst starved Beijing strains were not dependent on CF. Moreover, Beijing strains showed improved resuscitation with cognate CF, suggesting the presence of unique growth stimulatory molecules in this family. Analysis of starved Beijing and LAM strains showed longer cells, which with resuscitation were restored to a shorter length. Cell wall staining with fluorescent D-amino acids identified strain-specific incorporation patterns, indicating that cell surface remodeling during resuscitation was distinct between clinical strains. Collectively, our data demonstrate that M. tuberculosis clinical strains from different genotype lineages have differential propensities to generate DCTB, which may have implications for TB treatment success.

The detection of mixed tuberculosis infections using culture filtrate and resuscitation promoting factor deficient filtrate

Tuberculosis (TB) infected individuals harbor a heterogenous population of differentially culturable tubercle bacilli (DCTB). Herein, we describe how DCTB assays using culture filtrate either containing or deficient in resuscitation promoting factors can uncover mixed infections. We demonstrate that Mycobacterium tuberculosis (Mtb) strain genotypes can be separated in DCTB assays based on their selective requirement for growth stimulatory factors. Beijing mixed infections appear to be associated with a higher bacterial load and reduced reliance on growth stimulatory factors. These data have important implications for identifying mixed infections and hetero-resistance, which in turn can affect selection of treatment regimen and establishment of transmission links.