Emergence of Mycobacterium simiae: A retrospective study from a tertiary care center in Lebanon

Objective The objective of this study is to describe the clinical significance of Mycobacterium simiae at a major tertiary care center in Lebanon. Methods This is a retrospective study of patients with positive cultures for M. simiae isolated between 2004 and 2016 at the American University of Beirut Medical Center. Results This study included 103 M. simiae isolates recovered from 51 patients. Their mean age was 62.7 years. The majority were males and smokers. Specimens were mostly from respiratory sources (97%). Common comorbidities included chronic lung disease (such as chronic obstructive pulmonary disease), solid tumor, systemic disease, and diabetes mellitus. Productive cough and dyspnea were the most common symptoms. Frequent radiographic findings were infiltrates and nodules on chest X-ray and nodules, infiltrates, and bronchiectasis on chest computed tomography scan. Among 18 tested isolates, 5.8% were resistant to clarithromycin, 11.7% to amikacin, and 70-100% to other antimicrobials. Out of 13 patients receiving early treatment, 5 noted improvement, one had recurrence of symptoms, two received alternative diagnosis, and five died. Two of those deaths were related to M. simiae. Common treatment regimens included clarithromycin in different combinations with trimethoprim-sulfamethoxazole, moxifloxacin, and amikacin. Moreover, clofazimine was used in only two patients whose isolates were resistant to all but one agent. Duration of treatment ranged from 6-24 months. Conclusion In Lebanon, M. simiae is increasingly encountered with true infection rates of at least 47%. Furthermore, the prevalence of multidrug resistance among the Lebanese M. simiae isolates is very high limiting the treatment options.