Nontuberculous Mycobacteria (NTM) Overview Make an Appointment Find a Doctor Ask a Question Reviewed by Shannon H. Kasperbauer, MD (July 01, 2017) Bacteria, like plants and animals, have been classified into similar groups. The groups are called "families." One such family of bacteria is known as the Mycobacteriaceae. Within this family, there are a number of species. Some species can cause human diseases (pathogenic). Other species do not cause human diseases (saprophytic). For example, Mycobacterium tuberculosis is an infamous species. This is the organism that causes human tuberculosis. Mycobacterium leprae is the organism that causes leprosy. Nontuberculous mycobacteria (NTM) refers to all the species in the family of mycobacteria that may cause human disease, but do not cause tuberculosis (TB) or leprosy. In a U.S. study from 2010, it was estimated that approximately 30 people per 100,000 population were infected with these lesser-known "cousins" of TB and leprosy. In fact, for unknown reasons, data from across the globe note an increase in case rates of infection over time. The most common NTM that require treatment are M. avium complex, M. kansasii, M. abscessus, M. chelonae, M. fortuitum, M. terrae, M. xenopi and M. simiae. Among the NTM, there are three species which predominantly involve the skin: M. leprae, M. ulcerans and M. marinum. M. avium complex is the most common NTM to cause human infection in the U.S., and it makes up around 80 percent of the infections we treat at National Jewish Health. It is often referred to as MAC. It was formerly thought to be made up of two species, M. avium and M. intracellulare. With more sophisticated tools, we appreciate that there are at least 10 different species within this complex. The three main species to cause disease are M. avium, M. intracellulare and M. chimaera. Videos The NTM Lecture Series was held in Denver on May 15, 2015. Each lecture was video taped live and is available for viewing. Programs & Services Nontuberculous Mycobacterial (NTM) Infections Program NTM Center of Excellence Clinical Trials For more than 100 years, National Jewish Health has been committed to finding new treatments and cures for diseases. Search our clinical trials.