[Increase in the incidence of invasive pneumococcal disease caused by serotype 19A prior to the implementation of the expanded pneumococcal vaccines]

Abstract

Objective: To describe the epidemiology, clinical syndromes and microbiological characteristics of serotype 19A as the main cause of invasive pneumococcal disease (IPD) in children admitted to a tertiary hospital in Spain.

Methods: A retrospective (1998-2004) and prospective (2005-2009) study was conducted on children with IPD produced by serotype 19A. The study was divided into three periods (P): P1 (1998-2001) when PCV7 had not been commercialized; P2 (2002-2005) with 40% vaccine coverage among children; and P3 (2006-2009) when the vaccine was added to the Childhood Immunization Schedule in Madrid.

Results: A total of 155 isolates of Streptococcus pneumoniae (SP) producing IPD were analysed, with 21 of them being serotype 19A (14%). An increased prevalence of serotype 19A was found: 2/45 cases (4.4%) in P1, 3/41 cases (7.3%) in P2 and 16/69 cases (23.2%) in P3. It occurred mostly in children younger than 2 years (16/21; 76%). This serotype was the main cause of meningitis (5/20; 25%), pleural empyema (3/22; 14%) and bacteraemic mastoiditis (2/4; 50%). Thirteen isolates (61.5%) had an MIC ≥ 0.12μ/ml for penicillin in extra-meningeal infections, and 3 of the 5 isolates causing meningitis (60%) had an MIC ≥ 1μ/ml for cefotaxime.

Conclusions: Serotype 19A was the main causal agent of IPD in the PCV7 era (P3), with high antibiotic resistance rates. This serotype was responsible for all types of IPD, being the main cause of meningitis.

Keywords: 19A serotype; Enfermedad neumocócica invasiva; Heptavalent pneumococcal vaccine; Invasive pneumococcal disease; Serotipo 19A; Vacuna neumocócica heptavalente.