of M. abscessus subsp. bolletii BDT was completed in 2012. Since then, a large number of strains from this subspecies have had their genomes sequenced, leading to a clarification of subspecies boundaries. In 1992, M. abscessus was first recognised as a distinct species. In 2006, this group was separated into three subspecies: M. a. abscessus, M. a. bolletii, and M. a. massiliense. In 2011, the latter two were briefly merged into a single subspecies, but were subsequently separated again following greater availability of genome sequence data, which showed the three subspecies formed genetically distinct groups. It has been proposed that M. bolletii and M. massiliense be reinstated as unique species. These distinct groups also correspond to important biological differences. Clinically important differences include differing susceptibilities to antibiotics. M. a. abscessus and M. a. bolletii carry a common antibiotic resistance gene, which confers resistance to macrolide antibiotics, while M. a. massiliense is thought to carry a nonfunctional copy, so is more susceptible to antibiotics and more easily treated. Pathogenesis M. abscessus can cause lung disease, skin infections, central nervous system infections, bacteremia, eye infections, and other, less common diseases. Chronic lung disease occurs most commonly in vulnerable hosts with underlying lung disease such as cystic fibrosis, bronchiectasis, and prior tuberculosis. Clinical symptoms of lung infection vary in scope and intensity, but commonly include chronic cough, often with purulent sputum. Haemoptysis may also be present. Systemic symptoms include malaise, fatigue, and weight loss in advanced disease. The diagnosis of M. abscessus pulmonary infection requires the presence of symptoms, radiologic abnormalities, and microbiologic cultures. M. abscessus can cause skin infections in immunodeficient patients, patients who have recently undergone surgery, tattooing, or acupuncture, or after exposure to hot springs or spas. It can be associated with middle-ear infections (otitis media). The incidence of M. abscessus infections appears to be increasing over time. Outbreaks of M. abscessus have been reported in hospitals and clinical settings worldwide. While outbreaks of major clinical concern involve transmission (most likely indirect transmission) between vulnerable patients such as those receiving lung transplants or being treated for cystic fibrosis, outbreaks have also been reported at clinics providing cosmetic surgery, liposuction, mesotherapy and IV infusion of cell therapy, although these are more attributable to contaminated disinfectants, saline and instruments than contact between patients. Management Bacteriophage therapy A study from 2019 supported the capability of phages in killing resistant bacteria unable to be