Resistance to First-line Drugs in Clinical Isolates of Mycobacterium tuberculosis in Isfahan

Tuberculosis (TB) remains a serious public health problem worldwide, causing millions of deaths annually. It is estimated that one-third of the world population is infected with latent TB. Drug-resistant TB is considered a major and growing global threat. In this study, we aimed to indicate the drug-susceptibility of Mycobacterium tuberculosis isolates from patients, presented to Mollahadi Sabzevari Tuberculosis Center in Isfahan, Iran to the first-line drugs.

In this study, Mycobacterium tuberculosis was isolated from 438 patients with pulmonary tuberculosis referred to the Regional Reference Laboratory of tuberculosis in Isfahan province during 2017-2019, 33 resistant isolates were studied. Drug susceptibility testing to first-line drugs was performed by proportion method, and the H37Rv reference strain sensitive to all drugs was used for quality control.

Out of 438 isolates, 20 isolates (37.7%) were drug-sensitive and 33 isolates (62.3%) were resistant to the first-line drug by phenotypic method, which was isoniazid (INH) 22 isolates (66.7%), rifampin (RIF) 18 isolates (54.5%), ethambutol (EMB) 4 isolates (12.1%) and pyrazinamide (PZA) 5 isolates (15.2%) respectively. Also, 10 isolates (30.3%) were multidrug-resistant tuberculosis (MDR-TB).

The pattern of drug resistance in Mycobacterium tuberculosis is different in each region and in the Isfahan region due to the increasing drug resistance of tuberculosis. Further research is needed to determine the drug resistance of Mycobacterium tuberculosis.