NTM lung infections in CF patients on the rise: US Study

Highest number of new infections from 2010-2019 seen in the South

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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The annual number of new cases of nontuberculous mycobacteria (NTM) lung infections is increasing in the U.S. among people with cystic fibrosis, a study finds.

Between 2010 and 2019, the incidence, or new cases, of infections increased by 3.5% a year, with the highest number seen in the South. NTN is a type of bacteria in the environment.

While the development of new therapies has lowered the infection risk with CF, “continued surveillance for NTM lung infections is needed in both the CF and non-CF popula­tions to assess the burden of these infections and evaluate trends,” researchers wrote in “Incidence of nontuberculous mycobacteria infections among persons with cystic fibrosis in the United States (2010–2019),” which was published in BMC Infectious Diseases.

NTM are related to the bacteria that cause tuberculosis (a serious infection that mainly attacks the lungs) and are commonly found in soil, dust, and water.

People with a weakened immune system or underlying lung disease, including those with CF, are at higher risk of infection. The thick mucus that accumulates in multiple organs with CF, including the lungs, makes it harder for the immune system to clear an infection up.

A previous study led by researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, reported that the five-year prevalence of NTM lung infections among CF patients in the U.S. was 20% and increasing. The Cystic Fibrosis Foundation has collected data on NTM testing and results since 2010.

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Incidence of annual NTM infections

Here, NIAID researchers expanded their previous analysis and assessed the 10-year incidence of NTM pulmonary infections among people with CF. Since the prevalence (total number of cases at a particular time) of NTM pulmonary infections varies widely across the U.S. due to different environmental exposures, the incidence by region was also assessed.

The researchers analyzed data from the Cystic Fibrosis Foun­dation Patient Registry of CF patients, age 12 and older, who were tested for NTM from 2010-2019. Only participants with NTM culture results were included.

The results were used to calculate the average annual incidence of total NTM, as well as of the two most common types of it found in people with CF — Myco­bacterium avium complex and M. abscessus — at both the national and state levels.

The rate of NTM testing increased significantly over 10 years, from 19.1% in 2013 to 23.1% in 2019, a 1.1% annual increase.

In total, during this period, 3,771 incident NTM pulmonary infections were registered. This represented 18.4% of the total and the patients’ median age was 25 years. Among this group, 1,816 (48.2%) were due to M. avium complex and 960 (25.5%) were from M. abscessus infections.

Overall, the average annual incidence of NTM pulmonary infections among CF patients in the U.S. was 58 cases per 1,000 persons.

The highest total NTM pulmonary infection incidence, 64.1 cases per 1,000 persons tested, was in the South. Incidence of M. abscessus was also highest there — 20.3 cases per 1,000 persons tested. The incidence of M. avium complex infections was highest in the Northeast at 33.5 cases per 1,000 persons tested.

Overall, the annual incidence of total NTM pulmonary infections rose significantly — 3.5% per year. Significant increases in the annual percent change (APC) — a way to assess the increase over time — were seen in the North­east (an APC value of 7.7%), South (4.1%), and Midwest (4.4%). In the West, the 1.8% increase in APC was not significant.

The increase in NTM pulmonary infections was driven by M. avium complex infections — 4.4% per year overall and 11% per year in the North­east. No significant changes in M. abscessus incidence rates were observed during the study period.

“The continued increase in NTM lung infections among [patients with CF] represents a public health and clinical burden of NTM in the U.S.,” the researchers wrote.