Evolving Landscape of Paediatric Pneumococcal Meningitis in Argentina (2013-2023)

Abstract

The introduction of pneumococcal conjugate vaccination (PCV) into the Argentinian Childhood National Immunization Program in 2012 marked a significant milestone in public health. Our study aims to assess the impact of this intervention on pneumococcal meningitis cases, serotype distribution, and antimicrobial resistance among pediatric populations from 2013 to 2023. Specifically, we compared the early post-PCV period (2013-2014) to the late post-PCV period (2022-2023). A total of 333 pneumococcal isolates were analyzed between 2013 and 2023. Gold standard pneumococcal serotyping was performed to identify the serotypes associated with infection in children < 6 years in Argentina, and the agar dilution method was carried out to determine their profiles to antimicrobial agents. Our findings underscore the importance of PCV implementation, revealing notable shifts in pneumococcal epidemiology over the study period. The proportions of serotypes 1 (6.7% to 0.0%), 5 (5.6% to 0.0%), and 14 (7.8% to 1.8%) decreased, whereas the proportions of serotypes 10A (3.3% to 10.7%), 15B/C (2.2% to 10.7%), and 24B (0.0% to 8.9%) increased. The top five rated serotypes in the 2022-2023 period were serogroup 24 (21.4%), 10A (10.7%), 15B/C (10.7%), 23B (7.1%), and 12F (5.4%). Regarding antimicrobial resistance, we found that a total of 115/311 isolates (37%) were not suceptible to penicillin, and 2.9% were not suceptible to cefotaxime. Twenty-five percent of the isolates were microbial drug resistant, with resistance to penicillin, erythromycin, tetracycline/doxicycline, and/or cotrimoxazol. Among the PCV13 serotypes, 19A remained the most commonly associated with MDR. The non-PCV13 serotypes, particularly 24F, 24A, and 24B, were prevalent among MDR isolates. The observed trends demonstrate the need for the continued expansion of pneumococcal vaccination policies, including consideration for vaccines offering enhanced indirect protection, thereby extending benefits beyond the pediatric population to encompass adults as well. Such strategies are pivotal in reducing the burden of pneumococcal disease and safeguarding public health.

Keywords: Streptococcus pneumoniae; antimicrobial resistance; invasive pneumococcal disease; meningitis; pediatrics; pneumococcal serotypes; vaccines.

Figure 1

Comparation of cases summited to the NRL (National Reference Laboratory, INEI—ANLIS “Dr. Carlos G. Malbrán”) and to the SNVS. The plot represents isolates from individuals under 5 years old, as these are the data presented in SNVS. The number of cases reported to the SNVS was extracted from the Argentine National Epidemiological Bulletin (https://www.argentina.gob.ar/boletin-epidemiologico-nacional), last accessed on 11 September 2024.

Figure 2

(A) Pneumococcal meningitis cases submitted to the National Reference Laboratory (NRL) during the study period. (B) Boxplot illustrating the distribution of isolates by year (the individual points of the boxplot represent the number of isolates submitted to the NRL for each month); the black boxes represent the interquartile range (IQR). The difference between years was analyzed using the Kruskal–Wallis test with multiple comparisons.

Figure 3

(A) Proportion of PCV13 isolates versus non-PCV13 isolates in the different periods studied. (B) PCV13 isolate distributions. (C) non-PCV13 isolate distributions. (D) Jitterplot of vaccine serotypes by year (points representing 3% or higher are labeled with 50% transparency). NVT = non-vaccine type.

Figure 4

Comparative serotype distribution: 2013–2014 vs. 2022–2023 update.

Figure 5

PCV theoretical coverage. Considering the period of 2022–2023, our analysis revealed no statistically significant differences between PCV13 vs. PCV15, PCV20 vs. PCV24, or PCV21 vs. PCV25. Of the currently available vaccines, PCV20 achieved the highest theoretical vaccination coverage of 45% in the most recent period.

Figure 6

Vaccination status of the isolates studied. Criteria for non-vaccine eligibility indicate that the patients were not of the minimum age required for vaccination.