Molecular insights into macrolide resistant Mycoplasma pneumoniae isolates from outpatient clinics in Tehran, Iran.

The rising incidence of macrolide-resistant Mycoplasma pneumoniae (MRMP) in Asia is a significant public health concern due to its implications in severe diseases. However, limited reliable data is available on this topic from Iran. To address this gap, we carried out a study in Tehran focusing on antimicrobial susceptibility and genotype distribution of MRMP. Following the CLSI M43-A guidelines, we assessed the growth inhibition of 54 M. pneumoniae isolates from outpatient clinics using four antimicrobial agents including azithromycin, erythromycin, clindamycin, and levofloxacin. In addition, Multilocus sequence typing (MLST) was performed on 20 randomly selected MRMP isolates. Our findings revealed alarming high resistance rates to erythromycin (85.1%) and azithromycin (85.1%), with significantly lower rates for clindamycin (9.25%). Notably, all isolates were susceptible to levofloxacin. Clonal complex analysis identified CC1 as the predominant complex (65% of isolates), with ST3 (50%) and ST14 (15%) being the most prevalent sequence types. This study provides novel insights into antimicrobial resistance and molecular epidemiology of M. pneumoniae in Iran. The high rates of MRMP isolates underscores the strong need for continued monitoring and antimicrobial stewardship of M. pneumoniae infections.