Characterisation of physiological properties and pathogenic potential of Mycobacterium bovis L-forms.

Mycobacterium bovis (M. bovis) is a major causative agent of bovine tuberculosis, a chronic disease affecting cattle, other domestic and wild animal species, as well as humans, with an estimated global financial burden of $3 billion a year. Emerging multidrug resistant (MDR) strains of M. bovis pose serious challenge to agriculture and food security.
L-form switching is an understudied mechanism of antimicrobial resistance (AMR), which relies on a temporary loss of the bacterial cell wall during treatment with antibiotics that target this structure (e.g. penicillin). L-form switching allows bacteria to persist during antibiotic treatment and recur once antibiotics are no longer present. We have previously demonstrated that L-forms exist in patients with recurrent urinary tract infections and that they can survive inside the host immune cells (Nature Communications, 2019 and Cell, 2018). This novel, interdisciplinary project explores the potential of M. bovis to undergo L-form switching and how this might contribute to treatment and disease outcome.
The project consists of three work packages and an attenuated Mycobacterium bovis Bacille Calmette-Guérin (BCG) strain will be used to conduct the research:
i) Optimising requirements for induction and growth of Mycobacterium bovis BCG L-forms
L-forms are inducible by various cell wall targeting agents, including antibiotics and lysozyme, and require osmoprotective conditions for growth (to prevent bursting in the absence of the cell wall). A range of L-form inducing and osmoprotective agents at various concentrations will be
systematically tested as an additive to growth media, to obtain conditions optimal for efficient growth of mycobacterial L-forms in the laboratory.
ii) Characterizing interactions of host cells and Mycobacterium bovis BCG L-forms
We have previously observed that L-forms of major human pathogens including Staphylococcus aureus and Escherichia coli are capable of survival inside the host immune...