Nontuberculous Mycobacterial Infection and Pulmonary Disease in Northern Israel: A Focus on Mycobacterium simiae

The prevalence of nontuberculous mycobacteria (NTM) pulmonary disease is rising globally. Previously, we described a high prevalence of Mycobacterium simiae isolation in Israel.

What is the prevalence of NTM pulmonary disease and M simiae pulmonary disease in Northern Israel? Which factors are associated with mortality among people with NTM?

We retrospectively recorded all samples from Clalit Health Services-Haifa District reference mycobacteria laboratory for growth of NTM between January 2010 and March 2021. We manually reviewed a random sample of corresponding patients' electronic medical files and extracted demographic, clinical, and radiologic data, and data on the course of the disease. Univariate and multivariate analyses were performed to assess factors associated with features of NTM pulmonary disease and mortality.

A total of 2,968 clinical isolates from 1,501 people yielded NTM species. The relative abundance of M simiae, Mycobacterium avium complex (MAC), and other species increased over the study period. Among the 550 patient files reviewed, clinical presentation, fulfilment of established criteria for NTM pulmonary disease, and mortality rates were not significantly different between patients with M simiae, MAC, and Mycobacterium kansasii/Mycobacterium szulgai, with 27.7%, 35.3%, and 27.8% of people fulfilling criteria for NTM pulmonary disease. Factors associated with mortality included age, male sex, and immunosuppression. Compared with MAC isolation, M simiae was associated with elevated mortality (hazard ratio, 1.84; 95% CI, 1.05-3.23). The extrapolated national annual incidence rate of NTM pulmonary disease was 1.7 to 2.0 per 100,000 population.

Our results show that infection with M simiae is prevalent in Israel, and although considered minimally pathogenic, demonstrated similar clinical and radiologic features to MAC pulmonary disease.