798. The role of whole genome sequencing in characterizing the mechanism of action of anti-tuberculosis compounds: demonstrated with para-amino salicylic acid and its analogue
Session: Poster Abstract Session: Tuberculosis and Other Mycobacterial Infections
Thursday, October 4, 2018
Room: S Poster Hall
Posters
  • Poster798.pdf (309.5 kB)
  • Background: Para-aminosalicylic acid (PAS) was one of the first antibiotics to be used against tuberculosis (TB) and it is still one of the last remaining drugs available to treat extensively drug-resistant (XDR) disease. Despite being on the market for decades, the mechanism of action of PAS is not completely understood yet. Sixteen new compounds against Mycobacterium tuberculosis were created in the laboratory as salicylate analogues (based on their chemical structures) and their antimycobacterial activity had never been tested before. The main aim of this project was to test the activity of these new analogues and to understand their mechanism of action (including PAS).

    Methods: The compounds were tested using three different methods (spot culture, resazurin and MGIT system). Additionally, resistant mutants were created against PAS and the most promising analogue; whole genome sequencing (WGS) was performed to understand their mechanism of action.

    Results: One compound in particular, AD25a, showed the lowest critical concentration (0.04 µg/ml) among the salicylate analogues. The WGS analysis identified a total of 28 single nucleotide polymorphisms (SNPs) in the AD25a resistant mutants and 40 SNPs in the PAS resistant mutants (when compared to the reference strain H37Rv). The SNPs identified in the AD25a and PAS resistant mutants did not overlap. The genes rrs, rrl and folC were mostly involved in the PAS resistant mutants.

    Conclusion: The complete difference in the mutation profiles suggests that AD25a has a mechanism of action different to that of PAS, despite AD25a being synthesized as a salicylate analogue. WGS analysis of PAS resistant mutants has also provided some interesting results. In particular, all our PAS mutants showed mutations in the rrs and rrl genes (16S and 23S RNA genes, respectively). These mutations should affect the ribosomes and the overall synthesis of proteins. This highlights a new potential mechanism of resistance for PAS that has never been observed before.

    Giovanni Satta, MBBS MSc MBA FRCPath1,2, Adam A Witney, PhD3, Diepreye Ere, PhD4,5, Alex Disney, PhD5,6, Neelu Begum, MSc7,8, Julio Ortiz Canseco, PhD8, Colin Ratledge, PhD5, Andrew N Boa, PhD5 and Timothy D McHugh, Professor8, (1)Charing Cross Hospital, Microbiology, Imperial College Healthcare NHS Trust, London, United Kingdom, (2)Centre for Clinical Microbiology, University College London, London, United Kingdom, (3)St George's University of London, London, United Kingdom, (4)Niger Delta University, Amassoma, Nigeria, (5)University of Hull, Hull, United Kingdom, (6)University of Bath, Bath, United Kingdom, (7)King's College London, London, United Kingdom, (8)University College London, London, United Kingdom

    Disclosures:

    G. Satta, None

    A. A. Witney, None

    D. Ere, None

    A. Disney, None

    N. Begum, None

    J. Ortiz Canseco, None

    C. Ratledge, None

    A. N. Boa, None

    T. D. McHugh, None

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