The role of biomineralization in antibiotic resistance of M. abscessus biofilms

Mycobacterium abscessus is a biofilm-forming bacteria that cause human infections, including those of skin and central nervous system, and is associated with cystic fibrosis and chronic obstructive pulmonary disease. M. abscessus biofilm formation and morphology depends on surface glycolipids and free mycolic acids. M. abscessus biofilms are recalcitrant to antimicrobial drugs due to its high antibiotic resistance, the mechanism of which is still not clear. Previous studies have revealed that one mechanism contributing to virulence and antibiotic resistance within a bacterial biofilm is calcite biomineralization.

In this work, we are investigating the role of biomineralization in antibiotic resistance of M. abscessus biofilms. Initial results show that the morphology of M. abscessus biofilm colonies is calcium-dependent. Moreover, biofilms formed in the presence of calcium exhibit reduced diffusion of solutes – a potential mechanism of phenotypic antibiotic resistance. In addition, we observed that calcium-induced formation of a filament of the bacteria cells. Chemical inhibition of key biomineralization enzymes (urease and carbonic anhydrase) leads to the formation of defective biofilms and increased the diffusion of solutes through the colonies. These results suggest that calcification plays a role in M. abscessus biofilm development, and suggests its contribution to antibiotic resistance.