Increase in non-tuberculous mycobacteria isolated from humans in Tuscany, Italy, from 2004 to 2014

In Italy, the prevalence of non-tuberculous mycobacteria (NTM) in human infections is largely unknown. Herein, we report the epidemiology of NTM infections in a region of central Italy, Tuscany, over the last 11 years, and provide a review of the recent literature on NTM isolation rates in different geographic regions.

The complete collection of NTM strains isolated from a total of 42,055 clinical specimens at the Laboratory of Clinical Mycobacteriology of Pisa University Hospital, Italy, from 1 January 2004 to 31 December 2014 was included.

In our setting, in the period 2004-2014 a total of 147 patients had cultures positive for NTM. The number of NTM isolates increased considerably from five isolates in 2004 to 29 in 2014; a sharp increase occurred in the last 3 years. Overall, 16 NTM species were isolated; the most common were M. avium, M. intracellulare and M. gordonae detected in respectively in 41.5, 14.3 and 11.6% of NTM patients. In general, NTM isolates were largely prevalent in people older than 60 (57.8%); patients aged 1-10 year-old almost exclusively yielded M. avium and M. intracellulare. Of the 147 NTM clinical isolates, 76.2% were from respiratory specimens, 10.9% from lymph nodes, 2.7% from blood (yielding exclusively M. avium), and the remaining 10.2% from other clinical specimens.

The observed increase in NTM isolation rate in our setting is in keeping with the general increase in NTM infections reported worldwide in the past two decades, although the distribution of the NTM prevalent species differs by geographic region.