Nationwide surveillance of bacterial pathogens isolated from children by the surveillance committee of the Japanese society of chemotherapy, Japanese association for infectious diseases, and Japanese society for clinical microbiology between April 2021 and March 2024: General overview of pathogenic antimicrobial susceptibility

A nationwide surveillance program was conducted in Japan between April 2021 and March 2024 to assess the antimicrobial susceptibilities of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in pediatric patients aged <15 years with respiratory tract infections. A total of 1498 clinical isolates were collected from 18 medical institutions. Among 384 S. pneumoniae isolates, vaccine serotype coverage was 4.4 % for the 13-valent pneumococcal conjugate vaccine, 9.1 % for the 15-valent pneumococcal conjugate vaccine, and 30.2 % for the 20-valent pneumococcal conjugate vaccine. Serotype 35B was the most frequently isolated serotype. The proportion of S. pneumoniae isolates with penicillin G minimum inhibitory concentration ≥0.125 μg/mL increased compared with the 2017 survey, with serotypes 23A and 15A being the most common among less susceptible penicillin strains. Among 530 H. influenzae isolates, 9.2 % were β-lactamase-producing and 35.3 % were β-lactamase-non-producing ampicillin-resistant (BLNAR) strains, indicating a rise in BLNAR prevalence compared with the 2017 survey. Almost all of the H. influenzae isolates (98.3 % [521/530]) were non-encapsulated, and no capsular type b strain was detected. All 584 M. catarrhalis isolates were β-lactamase-producing strains, and one macrolide-resistant strain was identified for the first time in our surveillance program. These findings underscore the ongoing shifts in antimicrobial resistance and serotype distribution and provide information that will inform future treatment and prevention strategies.