• intracellular infection
• Mycobacterium abscessus
• phage therapy
• phages

Mycobacteria are classified as either tuberculosis-causing or non-tuberculous mycobacteria (NTM). Most NTM are environmental bacteria that can be found in soil and water sources and are non-pathogenic to humans. However, pathological conditions such as cystic fibrosis, can lead to NTM infections. Mycobacterium abscessus and Mycobacterium avium are the two major contributors to the rise in NTM infections
Mycobacteria are naturally resistant to many antibiotic molecules thanks to their peculiar cell wall, production of biofilm, possible intracellular lifestyle and the formation of granuloma in the host lungs that drastically decrease the drug activity.
The difficulty of the treatment calls for new therapeutic approaches and one of the most promising is phage therapy. It consists of exploiting the ability of phages to infect and lyse bacterial host cells.
The aim of the thesis work was to investigate the activity of phages against M. abscessus in vitro and ex vivo in THP-1 human macrophage cell lines.
Different phages were isolated from environmental samples. For the genotypic characterization, phage genomes were sequenced, assembled and annotated. For the phenotypic characterization the ability to infect clinical isolates of M. abscessus was tested with a host range assay. One-step growth assays were used to analyze the kinetics of infection and the burst size. The pH stability of these phages was tested. Lysis kinetics assays were performed to evaluate the lytic activity of a specific phage, Pisa 4, selected for the infection treatment. The intracellular activity of Pisa 4 was evaluated by treating intracellular infections of a clinical strain of M. abscessus in THP-1 macrophage cells.