Risk Factors Identified for Little-Known Lung Infections

Severe and sometimes fatal lung disease caused by a group of bacteria in the same family as those that cause tuberculosis is much more common than previously thought.

Nontuberculous mycobacteria (NTM) include more than 150 types of bacteria found in water and soil that can infect the lungs when inhaled, but unlike tuberculosis, NTM is not contagious and cannot spread from person to person.

Scientists at the University of Illinois (Chicago, IL, USA) analyzed mortality related to nontuberculous mycobacterial infections from 1999 through 2010 by examining multiple-cause-of-death data from the National Center for Health Statistics (Atlanta, GA, USA). They analyzed age-adjusted mortality rates, trends, associations with demographic variables, and comorbid conditions and correlated this information with similar data for tuberculosis-related mortality during the same time.

The investigators found that NTM was listed as immediate cause of death for 2,990 people, of whom 87% were 55 or older, 85% were white, and 52% were female. NTM-related deaths also correlated with smoking, cancer, human immunodeficiency virus (HIV) infection, and chronic obstructive pulmonary disease. They also found that the age-adjusted NTM mortality rates were uneven across the USA. Tuberculosis-related deaths among ethnic groups were also disproportional as among those with tuberculosis, 4,847 (59%) were white.

The team suggested that both warm and dry climates may contribute to NTM disease and influence on mortality by different environmental factors, such as temperature, soil and water conditions. NTM demonstrated a strong relationship with some comorbid conditions such as chronic obstructive pulmonary disease, chronic respiratory failure, bronchiectasis, HIV, interstitial lung diseases, rheumatoid arthritis, hematopoietic malignancies and tobacco use. The infection is treatable, but antibiotic therapy is expensive and can take up to two years. Examples of nontuberculous mycobacteria that should be distinguished from tubercle bacilli are Mycobacterium chelonae, M. abscessus, M. fortuitum, and M. cosmeticum

Mehdi Mirsaeidi, MD, MPH, the lead author said, “People and physicians need to be aware of NTM, especially as we see more of it, and because it can look like a lot of other pulmonary diseases. Patients usually present with a cough, and correct diagnosis can take years. Having a better understanding of the risk factors associated with NTM will give us a better chance of diagnosing it faster. This is important, because it's largely a curable infection.” The study was published on March 14, 2014, in the journal Public Library of Science ONE.

Related Links:
University of Illinois
National Center for Health Statistics