Different patterns of antimicrobial non-susceptibility of the nasopharyngeal carriage of Streptococcus pneumoniae in areas with high and low levels of PCV13 coverage.

Introduction: The impact of pneumococcal conjugate vaccines (PCVs) on antimicrobial resistance (AMR) in Streptococcus pneumoniae (Spn) among Chinese children remains inadequately characterized. Evidence is also limited on the interaction between vaccination coverage and regional disparities in AMR patterns. This study aims to assess the impact of the 13-valent pneumococcal conjugate vaccine (PCV13) on nasopharyngeal carriage of Spn and antimicrobial nonsusceptibility to commonly used antibiotics among healthy children under five years of age in China.

Methods: In 2022, 737 pneumococci were isolated from 2333 healthy children recruited in 4 areas (Haikou, Wanning, Baisha, and Qiongzhong) in Hainan Province, China. Serotyping and antimicrobial susceptibility tests were performed. Participants were divided into 4 groups based on individual PCV13 vaccination history and the local vaccination coverage rates: vaccinated and unvaccinated groups in the high-coverage area (group VH & NVH), and vaccinated and unvaccinated groups in the low-coverage areas (group VL & NVL). Descriptive statistics and logistic regression analysis were used to assess the vaccine impacts.

Results: PCV13-vaccinated children exhibited significantly lower carriage rates of vaccine-type serotypes (VTs) compared to unvaccinated children: 6B (7.0 % vs. 2.7 %, P < 0.01), 6A (4.2 % vs. 1.2 %, P < 0.05), and 23F (2.2 % vs. 0.3 %, P < 0.05). The non-susceptibility rates to erythromycin, azithromycin, clindamycin, tetracycline, penicillin, and cefuroxime were 92.3 %, 87.5 %, 81.2 %, 91.2 %, 38.9 % and 64.7 %, respectively, resulting in 82.9 % of isolates being multidrug-resistant (MDR), especially to VTs (92.4 %). Isolates from the high PCV13 coverage area were less resistant to penicillin, cefuroxime, erythromycin, azithromycin, clindamycin and SXT, and were less MDR than isolates from the low PCV13 coverage areas.

Conclusions: Nasopharyngeal carriage of Spn was highly resistant to common clinical antibiotics. PCV13 vaccination significantly decreased VTs carriage and antimicrobial nonsusceptibility. These results suggest that the widespread use of PCVs is likely to substantially affect NP carriage and antimicrobial nonsusceptibility.