Genotyping of Mycoplasma pneumoniae strains isolated in Japan during 2019 and 2020: spread of p1 gene type 2c and 2j variant strains

Tsuyoshi Kenri; Tsutomu Yamazaki; Hitomi Ohya; Michio Jinnai; Yoichiro Oda; Sadasaburo Asai; Rikako Sato; Nobuhisa Ishiguro; Tomohiro Oishi; Atsuko Horino; Hiroyuki Fujii; Toru Hashimoto; Hiroshi Nakajima; Keigo Shibayama

doi:10.3389/fmicb.2023.1202357

Genotyping of Mycoplasma pneumoniae strains isolated in Japan during 2019 and 2020: spread of p1 gene type 2c and 2j variant strains

Front Microbiol. 2023 Jun 19:14:1202357. doi: 10.3389/fmicb.2023.1202357. eCollection 2023.

Authors

Affiliations

¹ Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
² Wakaba Children's Clinic, Saitama, Japan.
³ Kanagawa Prefectural Institute of Public Health, Kanagawa, Japan.
⁴ Chigasaki Municipal Hospital, Kanagawa, Japan.
⁵ Asai Children's Clinic, Osaka, Japan.
⁶ Department of Pediatrics, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
⁷ Department of Clinical Infectious Diseases, Kawasaki Medical School, Okayama, Japan.
⁸ Kurashiki Central Hospital, Okayama, Japan.
⁹ Okayama Prefectural Institute for Environmental Science and Public Health, Okayama, Japan.
¹⁰ Department of Bacteriology, Nagoya University Graduate School of Medicine, Nagoya, Japan.

Abstract

We characterized 118 Mycoplasma pneumoniae strains isolated from three areas of Japan (Saitama, Kanagawa, and Osaka) during the period of 2019 and 2020. Genotyping of the p1 gene in these strains revealed that 29 of them were type 1 lineage (29/118, 24.6%), while 89 were type 2 lineage (89/118, 75.4%), thereby indicating that type 2 lineage was dominant in this period. The most prevalent variant of type 2 lineage was type 2c (57/89, 64%), while the second-most was type 2j, a novel variant identified in this study (30/89, 33.7%). Type 2j p1 is similar to type 2 g p1, but cannot be distinguished from reference type 2 (classical type 2) using the standard polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) with HaeIII digestion. Thus, we used MboI digestion in the PCR-RFLP analysis and re-examined the data from previous genotyping studies as well. This revealed that most strains reported as classical type 2 after 2010 in our studies were actually type 2j. The revised genotyping data showed that the type 2c and 2j strains have been spreading in recent years and were the most prevalent variants in Japan during the time-period of 2019 and 2020. We also analyzed the macrolide-resistance (MR) mutations in the 118 strains. MR mutations in the 23S rRNA gene were detected in 29 of these strains (29/118, 24.6%). The MR rate of type 1 lineage (14/29, 48.3%) was still higher than that of type 2 lineage (15/89, 16.9%); however, the MR rate of type 1 lineage was lower than that found in previous reports published in the 2010s, while that of type 2 lineage strains was slightly higher. Thus, there is a need for continuous surveillance of the p1 genotype and MR rate of M. pneumoniae clinical strains, to better understand the epidemiology and variant evolution of this pathogen, although M. pneumoniae pneumonia cases have decreased significantly since the COVID-19 pandemic.

Keywords: Mycoplasma pneumoniae; Mycoplasmoides pneumoniae; antigenic variation; infectious diseases surveillance; macrolide resistance; p1 gene genotyping; protective immunity; whole-genome single-nucleotide polymorphism.