A Report on Drug Resistance Patterns of Mycobacterium tuberculosis Isolates in Northern Iran

There are limited data on the Mycobacterium tuberculosis (MTB) drug resistance in regions located at the proximity of the Caspian Sea. We aimed to assess the drug resistance patterns of the MTB isolates to anti-tuberculosis drugs in patients from four northern provinces of Iran between April 2013 and March 2019.

Drug susceptibility testing (DST) was performed by culturing MTB isolates on the Lowenstein-Jensen medium using the proportion method.

Out of 963 MTB isolates, 927 (96.3%) were recovered from Iranian cases and 36 (3.7%) were from Afghan immigrants. Based on DST, 59 (6.1%) showed any drug resistance pattern, while 18 patients (1.9%) were multidrug-resistant (MDR) or rifampicin-resistant (RR). Resistance to streptomycin (STR), isoniazid (INZ), rifampicin (RIN), and ethambutol (ETL) was reported in 33 (3.4%), 28 (2.9%), 18 (1.9%), and 12 isolates (1.2%), respectively.

The rate of MDR/RR in four northern provinces of Iran was in line with previous reports from the World Health Organization. Due to proximity to the former Soviet Union, which had a high rate of MDR/RR isolates, the establishment of cross-border tuberculosis (TB) control strategies is recommended to reduce the possibility of MDR-TB transmission. Moreover, DST for all TB cases is recommended as an effective diagnostic tool for optimal monitoring and control of drug resistance in these areas. Future studies with a molecular epidemiology approach will be needed to evaluate the transmission dynamics of MTB in these regions.