Macrolide Resistance and Multilocus Sequence Typing Genotype Analysis of Mycoplasma pneumoniae Isolates in the Republic of Korea, 2023-2024.

OBJECTIVES

Mycoplasma pneumoniae is a major pathogen responsible for upper and lower respiratory tract infections, accounting for approximately 20-40% of community-acquired pneumonia cases. The infection occurs most frequently in adolescents, with periodic outbreaks occurring every 3-4 years. The present study aimed to characterize the molecular epidemiological features of M. pneumoniae strains isolated during the 2023-2024 epidemic in the Republic of Korea by analyzing macrolide resistance-associated mutations and multilocus sequence typing (MLST) genotypes.

METHODS

From January 2023 to December 2024, 1,294 respiratory specimens were collected through the Acute Respiratory Infection Network. Macrolide-resistant mutations in the 23S rRNA domain V (A2063G/A2064G) were analyzed in M. pneumoniae polymerase chain reaction (PCR)-positive specimens. In addition, 217 cultured isolates were further examined for resistant mutations and MLST genotypes.

RESULTS

Among 1,294 collected specimens, 431 (33.3%) were PCR-positive for M. pneumoniae, and 217 (16.8%) isolates were successfully cultured. The A2063G mutation was detected in 81.4% (351/431) of PCR-positive samples and 89.4% (194/217) of cultured isolates. MLST analysis identified four sequence types (STs): ST3 (89.9%) was predominant, followed by ST7 (6.5%), ST14 (1.8%), and ST17 (1.8%). The distribution of STs varied by resistant genotype, with ST3 (97.4%) predominating among resistant isolates and ST7 (52.2%) among susceptible isolates.

CONCLUSIONS

M. pneumoniae isolates collected in the Republic of Korea during 2023-2024 exhibited high rates of macrolide resistance (89.4%), with ST3 as the predominant genotype. Distinct MLST distributions were observed between resistant and susceptible strains, underscoring the need for continuous molecular surveillance to monitor periodic outbreaks and shifts in genotype.