Epidemiology, changing resistance trends and serotypes of Streptococcus pneumoniae in children in Chongqing, China, 2019-2024: a multicenter study.

Objective: To investigate the clinical characteristics, temporal trends in antimicrobial resistance, and distribution of bacterial serotypes of Streptococcus pneumoniae (S. pneumoniae)in children in Chongqing region from 2019 to 2024. Methods: S. pneumoniae isolates and corresponding epidemiological data were collected from multi-center laboratories. Antimicrobial susceptibility testing was performed in the central research laboratory for each study period from 2019 to 2024, and the results were interpreted according to the breakpoint criteria specified in the Clinical and Laboratory Standards Institute (CLSI) M100-S34 guidelines (2024 edition). Capsular serotyping of S. pneumoniae was performed using the capsular swelling test, and vaccine coverage rate were calculated. Results: A total of 17,180 S. pneumoniae isolates were isolated over six years, accounting for 17.2% of all clinically isolated pathogenic bacteria and 45.9% of all Gram-positive bacteria. The isolates were mainly obtained from respiratory tract specimens (97.9%), followed by blood specimens (1.1%). S. pneumoniae was predominantly isolated from preschool, toddler and Infants, with isolation rates of 32.5%, 30.5% and 25.9%, respectively, together accounting for 88.8% of all S. pneumoniae isolates. The detection rates of penicillin-susceptible S. pneumoniae (PSSP), penicillin-intermediate S. pneumoniae (PISP), and penicillin-resistant S. pneumoniae (PRSP) were 83.7% (14196/16964), 14.8% (2513/16964), and 1.5% (255/16964), respectively. During the study period, the resistance rate to penicillin, trimethoprim/sulfamethoxazole, erythromycin, clindamycin, cefotaxime, and cefepime presented a significant downward trend. Except for vancomycin and linezolid. the resistance rates to all tested drugs in the PRSP group were higher than those in the PSSP group. Among different age groups, the resistance rate to trimethoprim/sulfamethoxazole and clindamycin were highest in toddler stage children, whereas erythromycin resistance was highest in preschool children. The resistance rates to penicillin, chloramphenicol, cefotaxime, and cefepime also differed significantly across age groups. The resistance rates to trimethoprim/sulfamethoxazole, levofloxacin, and moxifloxacin were higher in non-IPD group than in IPD group, whereas chloramphenicol resistance was lower. The average annual detection of S. pneumoniae decreased in post-COVID-19, and, except for chloramphenicol, resistance rates to all other antibacterial drugs were lower than those in the pre-COVID-19 period. Thirteen serotypes were identified, except for 8 (1.3%) non-typeable isolates. The top five serotypes, 19F (n = 207, 34.5%),14(n = 65, 10.9%),19A (n = 61, 10.2%), 6B (n = 59, 9.8%) and 1 (n = 52, 8.7%), accounted for 74.1% of all isolates. PCV7, PCV10, and PCV13 covered 388 (64.6%), 440 (73.3%), and 501 (83.5%) strains, respectively. Conclusion: The resistance rates of S. pneumoniae to penicillin, trimethoprim/sulfamethoxazole, erythromycin, clindamycin, cefotaxime, and cefepime show significant downward trends over the six-year study period. The pneumococcal conjugate vaccine PCV13 can effectively cover the major drug-resistant serotypes in China, and PCV 13 is therefore recommended for the prevention of S. pneumoniae infection. These findings contribute to informed and clinical policy decisions for prevention and treatment.