Macrolide-Resistant Mycoplasma pneumoniae Among Japanese Children from 2008 to 2024

Mycoplasma pneumoniae (MP), an important pathogen that causes pneumonia among children and young adults, caused an epidemic every four years in Japan until 2016, with the next epidemic occurring eight years later in 2024. This study compared the prevalence of MP infections among Japanese children in 2024 to previous years using real-time polymerase chain reaction (PCR) and the p1 genotype determined using the PCR restriction fragment length polymorphism typing method from nasopharyngeal swab specimens. Of the 133 total isolates collected in 2024, 54.1% were macrolide-resistant MP (MRMP), with 98.0% of those containing an A2063G mutation in the 23S rRNA gene associated with macrolide resistance. This annual rate of MRMP and incidence of the A2063G mutation was similar to those in 2016. However, the dominant p1 genotype among isolates in 2024 was type 1 (93.4%), whereas type 2 was dominant in the previous epidemic. Thus, although the rate of MRMP in 2024 was similar to that in the previous epidemic year, the distribution of p1 genotypes was different. Further, the rate of MRMP was lower than neighboring Asian countries, including China and Korea, but was higher than in European countries. Therefore, it is important to continue monitoring MP infections in Japan.