Use of Nano- SIMS at the single cell-level to evaluate drug penetration into mycobacterial biofilms

Non-tuberculous mycobacteria (NTMs), such as Mycobacterium abscessus and chimaera, can cause high mortality and morbidity amongst patients who are immunocompromised or have chronic lung diseases, such as cystic fibrosis. Mycobacterial biofilms can form in the alveolar walls of such patients following inhalation from environmental reservoirs. Recently, pathogenic strains have been isolated from shower heads and hospital air conditioning units. Biofilms are notoriously difficult to eradicate and are associated with the development of increased antimicrobial resistance (AMR). Treatment for M. abscessus and chimaera infections often requires 2–3 antibiotics over 2 years. The question we want to address is whether the increased AMR and treatment time in NTM biofilm formation is due to lack of antibiotic penetration, resulting in non-therapeutic and AMR-generative levels, or the development of phenotypic and/or genetic resistance. In this project we will use Nano-SIMS (nano-scale secondary ion mass spectrometry) to measure penetration of the antibiotic bedaquiline (BDQ), used to treat NTM infections, into individual cells of NTM biofilms (M. abscessus and M. chimaera). Nano-SIMS maps the relative abundance of different ions down to the nano-scale and can be used to measure in profile through the biofilm. In addition, the minimum inhibitory concentration (MIC) and minimum duration for killing (MDK) of BDK will be measured to determine antibiotic susceptibility in biofilms and a planktonic growth control. Understanding the AMR generation and prolonged treatment in NTM biofilms could lead to improved mortality and morbidity. The development of novel treatment strategies could enhance treatment efficacy, reduce treatment duration and AMR development.