Anti-mycobacterial activity of phage-encoded lysterases

Mycobacterium abscessus is a non-tuberculous Mycobacterium (NTM) that is often associated with respiratory infections in persons with cystic fibrosis. High levels of antibiotic resistance make M. abscessus infections difficult to treat, highlighting the urgent need for alternative therapeutic strategies. Mycobacteriophage therapy-treatment of infections with viruses that infect Mycobacterium hosts-shows considerable promise, but the narrow host specificity of the current mycobacteriophage repertoire limits this approach to personalized therapies. Here, we characterize the anti-M. abscessus activity of mycobacteriophage-encoded Lysin B enzymes (lysterases). Lysterases are serine-esterases that cleave the ester bonds linking mycolic acids to either arabinogalactan or trehalose in the mycobacterial cell envelope to complete the lysis process. In this study, we explored their ability to kill a spectrum of clinically isolated M. abscessus strains when administered exogenously. Six phylogenetically distinct lysterases were purified, characterized on the surrogate M. smegmatis, and their activity against a diverse panel of 24 M. abscessus clinical strains was assessed. The enzymes exhibit a range of activities against these strains, but most have broad-spectrum activity with only minor variations among the M. abscessus isolates. However, the activities can be quite potent, resulting in up to six orders of magnitude of reduction in viability within 4 h with one activity unit of the enzymes, and act synergistically with amikacin. Overall, mycobacteriophage-encoded lysterases show considerable potential for antimycobacterial control, especially for topical applications.IMPORTANCEMycobacterium infections are clinically challenging, and there is a high failure of resolving Mycobacterium abscessus infections using antibiotics. Mycobacteriophages show promise in treating M. abscessus infections, but there is substantial variation among clinical isolates in their phage infection profiles. Mycobacteriophages are unusual in coding for lysis enzymes-lysterases-that target cell wall exposed constituents, and these can have potential antibacterial activity. Exploring the vast sequence diversity of thousands of phage-encoded lysterases identifies a subset that was expressed, purified, and tested for their ability to kill a broad range of M. abscessus clinical strains. Lysterases with the broadest and greatest activity offer substantial potential for treatment of M. abscessus infection, especially where they display synergism with current antibiotics.