Mohammad Azarsa - Department of Microbiology, Khoy University of Medical Sciences, Khoy, Iran.
Mehrdad Mosadegh - Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Soheila Habibi Ghahfarokhi - Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Mohammad Reza Pourmand - Department of Pathobiology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.

Background: The number of erythromycin-resistant Streptococcus pneumoniae has significantly increased around the world. The present study aimed to determine the serotype distribution and molecular epidemiology of the erythromycin-resistant Streptococcus pneumoniae (ERSP) isolated from patients with invasive disease. Methods: A total of ۴۴ Streptococcus pneumoniae isolates were tested for susceptibility to several antimicrobial agents. Additionally, the polymerase chain reaction (PCR) was applied to evaluate ERSP isolates in terms of the presence of erythromycin resistance genes (e.g., ermB and mefA). The isolates were serotyped using the sequential multiplex-PCR method, and molecular epidemiology was assessed through the multilocus sequence typing (MLST) analysis. Results: The results represented multidrug resistance (MDR) in approximately half of the pneumococcal isolates. Among ۲۲ ERSP isolates, ۲۰ (۹۰.۹%) and ۱۲ (۵۶%) ones contained ermB and mefA, respectively. Further, ۱۴ (۳۱.۸%), ۳ (۲۲.۷%), and ۱۹A (۱۸.۱%) were the common serotypes among the isolates. No significant correlation was observed between serotypes and erythromycin resistance genes. Furthermore, the MLST results revealed ۱۸ different sequence types (STs), the top ones of which were ST۳۱۳۰ (۳ isolates) and ST۱۶۶ (۳ isolates). Population genetic analysis disclosed that CC۶۳ (۳۲%), CC۱۵۶ (۱۸%), and CC۳۲۰ (۱۸%) were identified as the predominant clonal complexes. Conclusions: The ERSP isolates exhibited high genetic diversity. The large frequency of MDR isolates suggests the emergence of high resistant strains, as well as the need to implement vaccination in the immunization schedule of Iran. These accumulating evidences indicate that ۱۳-valent pneumococcal conjugate vaccines provided higher serotype coverage in the ERSP isolates.

Erythromycin Resistance, Genotyping Techniques, Multilocus Sequence Typing, Serotyping, Pneumococcal Vaccines.