What is Atypical Tuberculosis?

Atypical tuberculosis is form of lung disease resembling tuberculosis that is caused by non-tuberculous mycobacteria (NTM). These are bacteria in the Mycobacterium family that are not the casual agent of tuberculosis, Mycobacterium tuberculosis complex, or leprosy. There are a number of other species in this family that individuals are exposed to on a daily basis. Atypical tuberculosis generally afflicts people with compromised immune systems and is increasingly being seen in post-menopausal women. The disorder is extremely difficult to diagnose, and treatment can involve years of therapy with multiple antibiotics that can have severe side affects.

Another term for this disorder is mycobacteria other than tuberculosis (MOTT), or environmental mycobacteria. This group of bacteria is unusual in having a thick cell wall composed of materials that make them resistant to most antibiotics and disinfectant measures. The mycobacteria can generally survive in difficult conditions and are found throughout the environment in streams, marshes, and even in chlorinated water. The organisms are not spread from one individual to another, but are acquired from the environment through drinking, breathing, or contact with soil.

The symptoms are similar to those of standard tuberculosis and include a cough, fever, weight loss, lack of appetite, low energy levels, bloody sputum, and night sweats. Of a number of species that can cause this disorder, one of the most prevalent is a group of bacterial species that can be found in birds, like chickens. This is the Mycobacterium avium complex, or MAC. Infection with this group is a common side effect for patients with cystic fibrosis or HIV infection. It is not clear why the disease incidence is increasing in post-menopausal women.

The diagnosis of atypical tuberculosis involves culturing the mycobacteria from sputum and can take weeks to months. In the past, only a few hospitals and research laboratories had the expertise to identify the species involved, using traditional diagnostic methods, once the microbes had been cultured. The techniques of recombinant DNA have broadened the ability to identify particular species. Sequence differences in nucleic acids are currently a common way of delineating the different types of mycobacteria.

A proper identification of the particular type of Mycobacterium infecting a person is critical. Not every species causes disease. Doctors do not wish to subject patients to the rigors of treatment unnecessarily. The powerful antibiotics used to treat NTM infections frequently have drastic side effects.

Antibiotic resistance is very common among these types of bacteria. The species vary in their susceptibility to a particular antibiotic. The identification of the particular Mycobacterium found in a person’s lung allows for the appropriate combination of antibiotics to be used in treatment of atypical tuberculosis. It generally takes a combination of three to five different antibiotics that may need to be taken for as long as two years to cure this disorder.