Prevalence of Genital Mycoplasmas in Pregnant Women and Antimicrobial Susceptibility of Clinical Mycoplasma hominis Isolates in Japan

Data on antimicrobial resistance in Mycoplasma hominis in Japan are limited. This study investigated the prevalence of genital mycoplasmas, and the antimicrobial susceptibility of M. hominis clinical isolates. Vaginal specimens from asymptomatic pregnant women collected between 2023 and 2024 were analyzed using polymerase chain reaction (PCR) to detect Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma parvum, and Ureaplasma urealyticum. Antimicrobial susceptibility of 36 M. hominis clinical isolates collected between 2017 and 2024 was evaluated using the MYCOFAST RevolutioN ATB+ kit, E-test, and LYO2 broth method. Quinolone resistance-determining regions were sequenced in fluoroquinolone-resistant isolates, and tet(M) was assessed by PCR. Among 160 vaginal specimens, the prevalence of M. genitalium, M. hominis, U. parvum, and U. urealyticum was 1.3%, 4.4%, 28%, and 10%, respectively. Resistance rates to levofloxacin, moxifloxacin, tetracycline, and clindamycin were 19%, 11%, 0%, and 2.8%, respectively. Compared with the MYCOFAST RevolutioN ATB+ kit, the LYO2 broth method yielded similar resistance rates for levofloxacin and clindamycin but a higher rate for moxifloxacin. ParC Ser91Ile was detected in all isolates with levofloxacin MICs of ≥4 µg/mL, and GyrA Ser153Leu was additionally detected in isolates with moxifloxacin MICs of >4 µg/mL. Fluoroquinolone- and clindamycin-resistant M. hominis isolates were identified in Japan.