Characterization of Streptococcus pneumoniae isolates pre- and post-vaccine introduction in Brazil Open Access

Fraire, Marissa (Fall 2018)

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Introduction: It is estimated that around half a million children under the age of 5 die of pneumococcal disease every year worldwide. In Latin America, pneumonia is one of the leading causes of death and hospitalization for children under 5 years and in the elderly over 60 years. In 2010, the 10-valent pneumococcal conjugate vaccine (PCV) was established in Brazil’s National Immunization Program. The purpose of this thesis was to evaluate any changes in serotype, genotype, and antibacterial resistance after PCV introduction in Brazil.

Methods: We used a total of 476 randomly selected invasive pneumococcal disease (IPD) isolates from Brazil that were obtained as part of the Global Pneumococcal Sequencing project; 236 of the isolates were collected in the pre-vaccination period (2008-2009) and 240 were collected post-PCV instruction period (2012-2013).

Results: A total of 47 serotypes were identified. Overall, the five most prevalent serotypes pre-PCV, accounting for >60% of IPD isolates, were 14 (29.7%), 6B (11.9%), 3 (7.6%), 19A (6.4%), and 23F (5.9%), and post-PCV introduction were 14 (9.2%), 19A (8.8%), 3 (8.75%), 12F (4.58%), and 6A (4.58%), accounting for ~35% IPD isolates. Significant decreases were observed in two vaccine-type serotypes: 14 (p-value <0.0001) and 6B (p-value<0.0009). Overall, 85.1% of the isolates were resistant to >1 antibacterial drug; however, following PCV introduction, the proportion was 81.3%. Non-susceptibility (NS) against penicillin, meropenem, and ceftriaxone declined significantly after PCV introduction. There was a strong correlation between the presence of pilus genes and specific clonal complexes, with the majority of isolates belonging to either CC156 or CC236.

Conclusions: PCV introduction has been associated with a significant decrease (p-value <0.0001) in PCV10/13 serotypes. Ongoing surveillance in Brazil will allow monitoring for the continued evolution of the pneumococcal population, and measure vaccine impacts on serotype and antibacterial resistance. Understanding these changes could help guide the development of future vaccines and prevention strategies.

Table of Contents

1) Chapter 1: Introduction

4) Chapter 2: Summary of Published Data from Brazil (Literature Review)

10) Chapter 3: Methods

12) Chapter 4: Results and Discussion

18) Discussion

20) Strengths and Weaknesses

21) Implications

22) References

29) Tables

36) Figures

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