Tayla Smith Poster 2025

Miss Tayla Smith

Africa Health Research Institute & University College London, South Africa & UK

Investigating M. tuberculosis ΔleuDΔpanCD as an in vitro persister model

Poster Abstract

Despite continued effort and progress, eradication of tuberculosis (TB) disease remains a challenge. This is partly due to the presence of a small population of slow-growing and drug-tolerant cells, termed persisters. The presence of persisters is the basis for the extended TB treatment regimen of 4-6 months, have been linked to treatment failure and implicated as a contributing factor to latent TB infection. While these cells can arise as a result of stochastic variation, environmental stressors, such host-associated factors like as hypoxia, low pH, nutrient deprivation, and nitro-oxidative stress, have been tied to persister enrichment. This stresses the need for persister models that are modelled after these host-induced stresses and that can be applied as assets of drug discovery, in order to identify novel treatments and therapies that can assist with the goal of eradicating TB globally.

In this study, we exploited Mycobacterium tuberculosis ΔleuDΔpanCD, an attenuated double auxotroph, as an in vitro persister model. This strain has been validated as a model organism for M. tuberculosis research. We investigated the effect of leucine and pantothenate deprivation on the bacterial growth, with resolution down to a single-cell level. We utilised the dual reporter plasmid, pTiGc, which reports on both viability and replication dynamics, in conjunction with imaging flow cytometry and drug susceptibility testing to assess persister formation and confirm the drug-tolerant phenotype. We found that nutrient deprivation, particularly withholding pantothenate and supplementing with leucine for 72 h, enriched for a persister population that was tolerant of antibiotic treatment.

This work underscores the potential of M. tuberculosis ΔleuDΔpanCD as an in vitro persister model, providing insights into the mycobacterial replication dynamics under nutrient-depleted conditions. The study established a foundation for further model development, with emphasis on adapting its applicability for high-throughput screening and contributed to the knowledge of persister biology.

Biography

Tayla Juliet Smith is a PhD candidate in Immunity and Infection with University College London, doing her research at the Africa Health Research Institute in Durban. Her background is in mycobacteriology, and she received her MSc in Molecular Biology cum laude from Stellenbosch University for optimising an in vitro persister model using an attenuated M. tuberculosis strain. Her current work involves exploring TB disease immune dysregulation in well-controlled HIV.