The genus Mycobacterium has more than 120 well-characterized species. Although the incidence of tuberculosis has decreased over the studied period, other, non-tuberculous mycobacteria (NTM) are isolated more often. Since, Mycobacterium xenopi is the most frequent NTM isolate in Croatia we studied its epidemiology and clinical relevance.

We performed a retrospective study over a 25-year period determining epidemiology, radiological findings and clinical importance of M. xenopi infection, obtaining data from archives in health care institutions from all over the country.

We detected 40 patients with a positive isolate of M. xenopi. Twenty-four patients met American Thoracic Society criteria for pulmonary disease. Eighteen (90%) of treated patients were male, on average 61.7 years old. Nineteen (95%) patients lived in towns. Most of them had comorbid disease, 18 (90%), with chronic obstructive pulmonary disease (COPD) being the most frequent, found in 11 (55%) patients. All patients were immunocompetent. We found COPD as the most frequent comorbid disease in the group of patients with worse treatment response (n=8; 80%), while in patients with good treatment response COPD was less frequent (n=3; 30%). Differences in the proportions of patients with COPD were significant (p=0.037).

In patients with M. xenopi pulmonary infection, COPD is a predisposing condition, and as a comorbid disease, is an important prognostic factor for treatment response.