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

Poushali Chakraborty,Bishan Dass Radotra,Ashwani Kumar,Deepak Kaushal,Sapna Bajeli

doi:10.1038/s41467-021-21748-6

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.

Highlights

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
We analyzed whether DTT causes thiol-reductive stress in M. avium (Mav), M. abscessus (Mab), and M. fortuitum (Mfo) cultures similar to Mycobacterium tuberculosis (Mtb) cultures
We tested whether DTT exposure induces biofilm formation in Mav, Mab, and Mfo cultures agitated at slow speed

Summary

Introduction

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. Mycobacterium tuberculosis (Mtb) can form cellulose-containing biofilms in vitro, it remains unclear whether biofilms are formed during infection in vivo. In agreement with this behavior, Ojha et al have demonstrated that Mtb pellicle biofilms contribute to the exhibition of in vitro drug tolerance[11] Building on these observations, Ackart et al have recently shown that Mtb cells form biofilms adhered to the surface of the culture dish, harboring drug-tolerant bacilli encased in an extracellular matrix derived from lysed human leukocytes[12]. We have demonstrated that thiol reductive stress induces the formation of surface adherent Mtb biofilms[17] Since cellulose is absent in humans and other animal models, its presence around the Mtb cells in infected animals or human tissues could indicate the presence of Mtb biofilms in vivo[23,24]

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