Biofilm formation in the lung contributes to virulence and drug tolerance of Mycobacterium tuberculosis

Abstract

Tuberculosis is a chronic disease that displays several features commonly associated with biofilm-associated infections: immune system evasion, antibiotic treatment failures, and recurrence of infection. However, although Mycobacterium tuberculosis (Mtb) can form cellulose-containing biofilms in vitro, it remains unclear whether biofilms are formed during infection in vivo. Here, we demonstrate the formation of Mtb biofilms in animal models of infection and in patients, and that biofilm formation can contribute to drug tolerance. First, we show that cellulose is also a structural component of the extracellular matrix of in vitro biofilms of fast and slow-growing nontuberculous mycobacteria. Then, we use cellulose as a biomarker to detect Mtb biofilms in the lungs of experimentally infected mice and non-human primates, as well as in lung tissue sections obtained from patients with tuberculosis. Mtb strains defective in biofilm formation are attenuated for survival in mice, suggesting that biofilms protect bacilli from the host immune system. Furthermore, the administration of nebulized cellulase enhances the antimycobacterial activity of isoniazid and rifampicin in infected mice, supporting a role for biofilms in phenotypic drug tolerance. Our findings thus indicate that Mtb biofilms are relevant to human tuberculosis.

Surface-Shaving Proteomics of Mycobacterium marinum Identifies Biofilm Subtype-Specific Changes Affecting Virulence, Tolerance, and Persistence

“…CelA1 expression was recently linked with biofilm formation, antibiotic tolerance, and virulence in Mtb ( 9 ). Therefore, Mmr cells in planktonic and biofilm forms with/without CelA1 overexpression were also exposed to rifampicin to determine the MIC and minimum bactericidal concentration (MBC) for this bactericidal first-line TB drug.…”

“…The present study shows that Mmr grows in two different biofilm subtypes and that reduced CelA1 hydrolase activity is one of the main triggers of biofilm growth and increased tolerance to rifampicin in both biofilm subtypes. Studies on Mtb and M. smegmatis have demonstrated that cellulose filaments are vital structural constituents of mycobacterial biofilm ECMs as well as essential for biofilm formation and the development of tolerance/persistence ( 9 , 11 , 18 , 19 ). We also show that the Mmr biofilm subtypes show distinct morphologies, with SBFs containing lichen-like structures and PBFs consisting of ribbon-like cords under the same in vitro conditions.…”

“…Thus, this labile layer forming the first molecular interaction with the host/environment is likely to involve key factors contributing to persistence/adaptation and search of anti-TB targets. Although several studies on mycobacteria have pinpointed cellular pathways and proteins that affect the capsule/cell wall and biofilm formation ( 9 , 14 , 17 – 25 ), systematic investigation of the factors that directly interact with the surrounding environment is necessary to be able to maximize the power of antimycobacterial treatment therapies.…”

Screening of Compounds for Anti-tuberculosis Activity, and in vitro and in vivo Evaluation of Potential Candidates

“…Genes essential for mycobacterial growth ( Sabine et al, 2015 ; Zuniga et al, 2015 ), enzymes associated with fatty acid synthesis ( Tiago et al, 2019 ), and DNA replication have been targeted for new treatment options ( Aggarwal et al, 2017 ; Pradhan and Sinha, 2018 ). However, clinical investigations revealed that the main mechanisms of drug resistance in Mtb are gene mutations and biofilm formation ( Poushali et al, 2021 ; Saba et al, 2021 ). Therefore, screening of natural products and their derivatives ( Guzman et al, 2012 ), new small molecule inhibitors ( Mishra et al, 2018 ), and FDA-approved drugs offers a new approach for the development of novel anti-TB drugs ( Igarashi, 2017 ; Luo et al, 2017 ; Igarashi et al, 2018 ; Nadav et al, 2018 ).…”

Surface-Shaving Proteomics ofMycobacterium marinumIdentifies Biofilm Subtype-Specific Changes Affecting Virulence, Tolerance and Persistence

“…The complex mycobacterial cell wall, involving capsule and outer/inner membranes connected by a dense mycolyl-arabinogalactanpeptidoglycan with high lipid levels, is the main barrier that protects the bacterial cells against drugs (6). While the mechanisms leading to drug tolerance in TB have remained poorly understood, biofilm formation was recently indicated as one of the strategies to increase viability, tolerance and persistence (7)(8)(9)(10).…”