Extracellular DNA of slow growers of mycobacteria and its contribution to biofilm formation and drug tolerance

Abstract

DNA is basically an intracellular molecule that stores genetic information and carries instructions for growth and reproduction in all cellular organisms. However, in some bacteria, DNA has additional roles outside the cells as extracellular DNA (eDNA), which is an essential component of biofilm formation and hence antibiotic tolerance. Mycobacteria include life-threating human pathogens, most of which are slow growers. However, little is known about the nature of pathogenic mycobacteria’s eDNA. Here we found that eDNA is present in slow-growing mycobacterial pathogens, such as Mycobacterium tuberculosis, M. intracellulare, and M. avium at exponential growth phase. In contrast, eDNA is little in all tested rapid-growing mycobacteria. The physiological impact of disrupted eDNA on slow-growing mycobacteria include reduced pellicle formation, floating biofilm, and enhanced susceptibility to isoniazid and amikacin. Isolation and sequencing of eDNA revealed that it is identical to the genomic DNA in M. tuberculosis and M. intracellulare. In contrast, accumulation of phage DNA in eDNA of M. avium, suggests that the DNA released differs among mycobacterial species. Our data show important functions of eDNA necessary for biofilm formation and drug tolerance in slow-growing mycobacteria.

Catheter-associated Mycobacterium intracellulare biofilm infection in C3HeB/FeJ mice

“…Notably, NTM can survive in any natural environment with water, as it forms biofilms in tap water pipes, supply and drainpipes of swimming pools and public bathhouses, inside shower heads, and in the tanks of household washing machines 23 – 25 . Matrix-like biofilm formation of Mtb and NTM has also been observed under laboratory conditions 26 – 28 . Recent studies have revealed enhanced biofilm formation in M. avium under hypoxic and eutrophic conditions, suggesting hypoxia adaptation in granulomas and links to dormancy 29 – 31 .…”

Healthcare-Associated Infections Caused by Mycolicibacterium neoaurum

“…The ability of RGM to cause medical device infections and subsequent need for device removal to eradicate infection has been attributed in part to RGM biofilm formation ( 39 ). Not all RGM produce biofilms, however, and biofilm formation by M. neoaurum has not been specifically investigated ( 40 – 42 ). Failure to remove CVCs in patients with catheter-associated bacteremia was associated with treatment failure in our case series; however, the small number of cases precludes a precise estimate of risk.…”

A laboratory perspective on Mycobacterium abscessus biofilm culture, characterization and drug activity testing

“…Indeed, eDNA is reported as an important constituent of M. abscessus biofilms across various culture media and subspecies ( Rose et al, 2015 ; Belardinelli et al, 2021 ; Chakraborty et al, 2021 ; Dokic et al, 2021 ; Oschmann-Kadenbach et al, 2024 ). An increase in eDNA, likely actively released, has been linked to biofilm maturation ( Belardinelli et al, 2021 ; Ilinov et al, 2021 ). The increase in eDNA during biofilm maturation was found to be more pronounced compared to other constituents of the ECM, such as sugars and proteins ( Belardinelli et al, 2021 ).…”