Pulmonary disease caused by Mycobacterium simiae in Iran's national referral center for tuberculosis

Several species of non-tuberculosis mycobacteria (NTM) can affect humans and can cause either symptomatic or asymptomatic infection.  This study aimed to determine the clinical and radiological manifestation, as well as the treatment, of M. simiae in patients in Masih Daneshvari Hospital, a TB referral hospital in Iran.

This retrospective study involved all patients presenting to our referral center from 2002 to 2009, with confirmation of M. simiae pulmonary infection. For all patients, sputum smear and culture for identification was performed, as was drug susceptibility testing. Additionally, PCR identification methods for NTM, and high-resolution CT scan were conducted. All patients were treated according to American Thoracic Society recommendations.

In total, 26 cases of M. simiae were identified in our center. The mean age of the patients was 58.23 ± 16.9years. Only one patient was HIV positive, and all but one were Iranian. The most frequent symptom was coughing (92.3%), and 100% of the patients had nodular lesions. In addition, bronchiectasis and cavitation were present in 84.6% and 88.5% respectively. All the patients were resistant to every first-line drug. Two patients failed the treatment, and twenty-four were cured, after which no recurrence of the disease was observed.

M. simiae may present with clinical and radiological manifestations consistent with tuberculosis, and be resistant to anti-TB agents. A more efficient treatment for NTMs such as M. simiae is needed, to shorten the period of treatment and proved fewer adverse effects than current therapies.