Studies Investigate Extent of Nontuberculous Mycobacterial Infections

Nontuberculous mycobacteria (NTM) can result in pulmonary and extrapulmonary infections and are primarily acquired from environmental sources, including soil and water exposed surfaces. Recent studies investigated the risk factors of NTM infections and their prevalence among patients in the United States.

One study used a national database of inpatient hospital encounters in order to characterize the epidemiology of skin/soft tissue (SST) and disseminated NTM infections.¹ Clinical, demographic, and laboratory data was analyzed from the Cerner Healthfacts database for patients with NTM from 156 hospitals from 2000 to 2015.

A total of 63,382,356 hospital-based patients were included in the study. Of the total patients, 1193 had extrapulmonary NTM, including 651 patients with SST, and 584 patients with disseminated infections in their blood and other organs. Additionally, 53 patients also had pulmonary NTM and 42 had both SST and disseminated infections.

The results also reported the most common comorbidities as fungal infections (16%), and HIV (14%). A total of 50 deaths were reported, including 28 with disseminated infections, 19 with SST, and 3 cases with both.

Furthermore, most of the cases had Mycobacterium avium complex (MAC) (53%), followed by M. fortuitum complex (8%), M. abscessus (7%), M. gordonae (7%), M. chelonae/abscessus (6%), other rapid growers (5%), and other species (5%). Also, more cases with HIV, pulmonary NTM, or fungal infections had MAC than those without.

When considering geography, the proportion of cases with SST infections ranged from 46% in the South to 69% in the West; for disseminated cases it ranged from 35% in the West to 58% in the South. Also, it was noted that most M. abscessus cases were in the South and most MAC cases were in the Northeast.

“This finding has important implications for clinical management of these complex patients, as more effective treatments exist for MAC relative to other NTM species,” concluded the research.

Another study tested the researchers’ hypothesis that the prevalence of NTM infection would be greater in recipients of drinking water treated with chloramine compared to drinking water treated with chlorine.²

The researchers performed a retrospective review and collected data from all NTM diagnostic tests performed at Michigan Medicine from January 2000 through September 2015. Data on municipal water treatment practices in Michigan cities was collected from the Environmental Protection Agency.

A total of 29,789 patients were tested for NTM over the study period and 4.1% had a positive test for NTM at least once—66% of these positive tests were from a pulmonary source. The patient diagnosis of immune deficiency or lung disease, and an older patient age, were associated with an increased risk of an NTM positive test.

While municipal water disinfectant type (chloramine) was not significantly associated with NTM infection, the use of surface water as opposed to groundwater as the primary drinking water source was associated with NTM infection.

“The positive relationship between a surface water source of municipal drinking water and NTM infection implies the potential for higher NTM abundance in surface water relative to groundwater, and suggests municipal drinking water as a potentially modifiable risk factor to reduce incidence of NTM infection,” concluded the study.

References

1. Lai E, Ricotta E, Prevots D.Epidemiology of extrapulmonary nontuberculous mycobacterial infections among hospitalized patients in the United States. Presented at the American Thoracic Society 2018 International Conference. May 20, 2018; San Diego, California. Abstract A2605.

2. Caverly L, Kotlarz N, Zimbric M, Errickson J, Raskin L, LiPuma JJ. Municipal drinking water treatment practices and risk of nontuberculous mycobacterial infection. Presented at the American Thoracic Society 2018 International Conference. May 20, 2018; San Diego, California. Abstract A2604.