Increasing and More Commonly Refractory Mycobacterium avium Pulmonary Disease, Toronto, Ontario, Canada.

In mid-2014, Public Health Ontario Laboratories identified coincident increasing Mycobacterium avium isolation and falling M. xenopi isolation in the Toronto, Ontario, Canada, area. We performed a retrospective cohort of all patients in a Toronto clinic who began treatment for either M. avium or M. xenopi pulmonary disease during 2009-2012 (early period) or 2015-2018 (late period), studying their relative proportions and sputum culture conversion. We conducted a subgroup analysis among patients who lived in the Toronto-York region. The proportion of patients with M. avium was higher in the late period (138/146 [94.5%] vs. 82/106 [77.4%]; p<0.001). Among M. avium patients, conversion was lower in the late period (26.1% vs. 39.0%; p = 0.05). The increase in the proportion of patients with M. avium pulmonary disease and the reduction in the frequency of sputum culture conversion is unexplained but could suggest an increase in environmental M. avium exposure.