Emergence of serotype 19A Streptococcus pneumoniae after PCV10 associated with a ST320 in adult population, in Porto Alegre, Brazil.

M.P Mott,K Pizzutti,G.R Cunha,M.M Del Maschi,P D'Azevedo,J Caierão,C.A.G Dias

doi:10.1017/s0950268819000013

Abstract

Use of pneumococcal conjugate vaccines has caused emergence of non-vaccine serotypes. No Brazilian data specifically about serotype 19A are available. We aimed to evaluate the frequency of occurrence, susceptibility profile and molecular epidemiology of serotype 19A before and after vaccine introduction in Brazil. Pneumococcal identification was performed by the conventional method. Strain serotype was determined by multiplex polymerase chain reaction (PCR) and/or Quellung reaction. Resistance was determined by Etest® and PCR was performed to determine the presence of macrolide resistance genes, ermB and/or mefA. Pneumococci were typed by Multilocus Sequence Typing. Thirty-eight serotype 19A Streptococcus pneumoniae were recovered, mostly from invasive diseases. Prevalence of serotype 19A increased following vaccination (from 3.5% before vaccination to 8.1% after, p = 0.04196). Non-susceptibility increased to most antimicrobials after vaccine introduction and was associated with clonal complex (CC)320. MLST showed nine different STs, which were grouped in one main CC: CC320 (63.9%). During the post-vaccination era, the frequency of this serotype increased significantly from 1.2% in 2011 to 18.5% in 2014 (p = 0.00001), with a concomitant decrease in the genetic variability: ST320 consistently predominated after vaccine-introduction (61.1%). Overall, our results showed a post-PCV10 increase in the frequency of serotype 19A. This was accompanied by a selection of CC320 and antimicrobial resistance.

Highlights

Infections caused by Streptococcus pneumoniae are a public health problem worldwide, notably in developing countries, where there are high rates of mortality and morbidity [1, 2]
Isolates obtained from invasive pneumococcal disease (IPD) were the most frequent origin of pneumococci, representing 74.3% (422/568), whereas 17 pneumococci were from unknown specimens
While data from Latin America and Caribbean showed that, from 1990 to 2010, the frequency of serotype19A increased from 1.5 to 4.9% [28], a study conducted by Santos et al, demonstrated a stable incidence of serotype 19A among Brazilian children, soon after PCV10 implementation [13]

Summary

Introduction

Infections caused by Streptococcus pneumoniae are a public health problem worldwide, notably in developing countries, where there are high rates of mortality and morbidity [1, 2]. In the year 2000, a conjugate 7-valent polysaccharide formula (PCV7) was introduced, targeting the most frequent serotypes causing infectious diseases (4, 6B, 9 V, 14, 18C, 19F, and 23F). Thereafter an increased prevalence in non-PCV7 serotypes was observed in invasive pneumococcal disease (IPD) [4,5,6,7,8,9]. In Brazil, only the 10-valent vaccine (PCV10) is licensed for use in the public system and does not target serotype 19A. The positive impact of PCV10 has been clearly observed, with a decrease in the incidence of vaccine-targeted serotype-specific IPD, as well as child mortality rates and pneumonia hospitalisation [12,13,14,15,16]. The emergence of non-PCV10 serotypes – including 19A – has been recognised [6, 8, 9, 11, 14, 17]

Objectives

Methods

Results

Conclusion