Molecular drug susceptibility testing against the first-line (rifampin and isoniazid) and second-line (ciprofloxacin–amikacin and kanamycin) treatment in different subtypes of Mycobacterium simiae

Abstract

© 2016 Objective background Mycobacterium simiae has been identified as the most prevalent slow growing mycobacteria that has been isolated among Iranian patients. Due to an importance of molecular approaches in the treatment of nontuberculosis mycobacteria, this study aimed to evaluate molecular drug susceptibility testing against the first-line (rifampin and isoniazid) and second-line (ciprofloxacin–amikacin and kanamycin) treatment in different subtypes of M. simiae. Methods The study involved all patients presenting to our referral tuberculosis center from March 2014 to August 2016, with confirmation of M. Simiae. For all sputum samples, after digestion and decontamination, followed by DNA extraction, polymerase chain reaction-restriction fragment length polymorphism was performed using the hsp65 gene. Furthermore, susceptibility to rifampin, isoniazid, ciprofloxacin, amikacin, and kanamycin were evaluated using rpoB, inhA, katG, gyrA, and rrs genes, respectively. Results In total, 60 cases (58.33% men and 41.66% women) of M. simiae infections were identified and all were confirmed as subtype I. All the patients were resistant to the first line-tuberculosis drugs, while 88.33% and 91.66% of cases were susceptible to ciprofloxacin and both amikacin and kanamycin, respectively. Conclusion Regarding the given result, first-line tuberculosis drugs should be excluded from the treatment regimen of M. simiae patients. In addition, subtype I seems to be the most or even the only isolated M. simiae subtype among all Iranian patients. While both amikacin and kanamycin drugs showed better efficacy in the treatment M. simiae, the most susceptible antibiotic is still indeterminate.