Vaccine 30 (2012) 3857–3861 Contents lists available at SciVerse ScienceDirect Vaccine jou rn al h om epa ge: www.elsevier.com/locate/vaccine Streptococcus pneumoniae serotypes isolated from the middle ear fluid of Costa Rican children following introduction of the heptavalent pneumococcal conjugate vaccine into a limited population Silvia Guevara a , Arturo Abdelnour a , Carolina Soley a,b , Nurith Porat c , Ron Dagan c , Adriano Arguedas a,b,∗ a Instituto de Atención Pediátrica, San José, Costa Rica b Universidad de Ciencias Médicas, San José, Costa Rica c Pediatric Infectious Disease Unit, Soroka University Medical Center and the Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel a r t i c l e i n f o Article history: Received 2 February 2012 Received in revised form 26 March 2012 Accepted 4 April 2012 Available online 19 April 2012 Keywords: Streptococcus pneumoniae Serotypes Otitis media Vaccines a b s t r a c t Background: The heptavalent pneumococcal conjugate vaccine (PCV-7) was introduced in high risk chil- dren and into the private market in Costa Rica in 2004 (<5% annual birth cohort). The aim of this study was to compare the Streptococcus pneumoniae serotype (ST) distribution, antibiotic resistance patterns and potential coverage before and after partial introduction of PCV-7. Methods: A comparison between the S. pneumoniae isolates obtained and serotyped from the middle ear fluid (MEF) of Costa Rican children with otitis media between years 1999 and 2003 (before PCV-7 usage) and those isolates obtained from 2004 to 2008. Results: A total of 145 and 218 MEF S. pneumoniae were serotyped between years 1999 and 2003 and 2004 and 2008, respectively. Considering a 19F outbreak observed between years 1999 and 2003, the following statistically significant changes in serotype distribution were detected between1999 and 2003 and 2004 and 2008: ST 3: 4.8–12.8% (P = 0.01); ST 11A: 0–4.1% (P = 0.01); ST 14: 3.5–21.1% (P < 0.001) and ST 19F: 52.4–18.3% (P < 0.05). Comparison of the two study periods demonstrated that during 2004 and 2008 a statistically significant decrease in penicillin non-susceptible serotypes (36.2–20.4% [P = 0.003]) and a statistically significant increase in trimethoprim-sulfametoxazole resistant serotypes (54.9–68.5%, respectively [P = 0.03]) was observed. Potential pneumococcal vaccines coverage between 1999 and 2003 and between 2004 and 2008 were: for PCV-7: 77.2–60.5%, respectively (P = 0.001); for the 10-valent con- jugated vaccine (PCV-10): 78.6–61.4%, respectively (P = 0.0008) and for the 13-valent conjugated vaccine (PCV-13): 84.8–79.3%, respectively (P = 0.2). Conclusions: Changes in the serotype distribution and antimicrobial susceptibility of MEF S. pneumoniae have been observed in Costa Rican children with OM. Because of the limited use of PCV-7 during the study period, these changes probably cannot be attributed to PCV-7 use. Between 2004 and 2008, PCV-13 offered the highest potential vaccine coverage. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Streptococcus pneumoniae is the most frequent pathogen iso- lated from the middle ear fluid (MEF) of Costa Rican children with otitis media (OM) and worldwide [1–4]. Based on the results of two efficacy clinical trials, the heptavalent pneumococcal conju- gated vaccine (PCV-7) was approved in the United States of America in 2000 for the prevention of OM episodes caused by the seven serotypes included in the vaccine [5,6]. ∗ Corresponding author at: Instituto de Atención Pediátrica, P.O. Box 607-1150, La Uruca, San José, Costa Rica. Tel.: +1 506 22332301; fax: +1 506 22213894. E-mail address: aarguedas@iped.net (A. Arguedas). Following the introduction of PCV-7 in the National Immuniza- tion Program (NIP) of different countries, the effectiveness of PCV-7 in OM has been compared with historical data before introduction of PCV-7 and an important reduction in the number of ambulatory visits for OM (42.7%), in the number of antimicrobial prescriptions for the treatment of OM (41.9%) and in the number of antimicrobial resistant S. pneumoniae isolates have been documented following PCV-7 introduction [7–9]. Of interest, various studies have also demonstrated that PCV-7 vaccinated children had a reduction in the number of recurrent OM episodes and tube insertions rates when compared against non-PCV-7 vaccinated children [7,10]. The reduction in S. pneumoniae OM episodes following PCV-7 introduction has been associated with a proportional increase in non-typable H. influenzae and pneumococcal non-PCV-7 serotype disease, particularly serotypes 3 and 19A [11,12]. 0264-410X/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.vaccine.2012.04.010