title: The impact of private use of PCV7 in 2009 and 2010 on serotypes and antimicrobial resistance of Streptococcus pneumoniae carried by young children in Portugal: Comparison with data obtained since 1996 generating a 15-year study prior to PCV13 introduction.
abstract: In Portugal, the 7-valent pneumococcal conjugate vaccine (PCV7) was not introduced in the national immunization plan but was commercially available between 2001 and 2010. We studied serotype distribution and antibiotic susceptibility of Streptococcus pneumoniae carried by children in 2009 and 2010. Vaccination with PCV7 was extracted from children's immunization bulletins and information on recent antimicrobial consumption was obtained through a questionnaire. For comparison, we included data from previous studies conducted since 1996: 1996-1999, 2001-2003, 2006-2007. Pneumococci were isolated from nasopharyngeal samples of 1092 children up to six years old attending day-care in an urban area. Among these, 76% (819/1070) were vaccinated and 62% (677/1092) carried pneumococci. In 2009-2010, serotype replacement was extensive. Carriage of PCV7 serotypes was 4.9% and 5.8%, in 2009 and 2010, respectively, with the majority being of serotype 19F (carried by 4.3% and 4.6% of all participants, respectively). Colonization by serotype 19F was associated with vaccine status (7.7% (19/248) of non-vaccinees vs. 3.5% (29/818) of PCV7-vaccinees, p=0.010). Carriage of serotype 19A was high in 2009 and 2010 (8.6% of all participants) consistent with values already observed in 2007; carriage of serotype 6A was <1% (10/1092), indicating a major decline after 2007 (5.8% or 31/538, p<0.001). Non-vaccine serotypes increased and serotype 6C became the most frequently carried serotype in 2010 (11.2% (54/481)). High-level resistance to penicillin (MIC ≥2mg/L) showed a decreasing trend (p<0.001), whereas resistance to both penicillin and erythromycin increased (p<0.001) and was detected in 15-20% of all isolates in 2009-2010, most of which were non-vaccine serotypes. Antimicrobial use decreased over time (p<0.001). In conclusion, widespread private use of PCV7 has impacted on colonization leading to near elimination of all PCV7 serotypes except for serotype 19F. Antimicrobial consumption declined but it may be too soon to observe generalized changes in antimicrobial resistance rates.
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Sónia
authors.initials: S
authors.lastname: Nunes
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Sofia
authors.initials: S
authors.lastname: Félix
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Carina
authors.initials: C
authors.lastname: Valente
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Alexandra S
authors.initials: AS
authors.lastname: Simões
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Débora A
authors.initials: DA
authors.lastname: Tavares
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Sónia T
authors.initials: ST
authors.lastname: Almeida
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal.
authors.forename: Ana C
authors.initials: AC
authors.lastname: Paulo
authors.affiliation: Private Pediatric Clinic, Lisbon, Portugal.
authors.forename: António
authors.initials: A
authors.lastname: Brito-Avô
authors.affiliation: Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal; Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, NY, USA.
authors.forename: Hermínia
authors.initials: H
authors.lastname: de Lencastre
authors.affiliation: Laboratory of Molecular Microbiology of Human Pathogens, Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB/UNL), Oeiras, Portugal; Laboratory of Molecular Genetics, ITQB/UNL, Oeiras, Portugal. Electronic address: rsaleao@itqb.unl.pt.
authors.forename: Raquel
authors.initials: R
authors.lastname: Sá-Leão
mesh_terms: D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000453:epidemiology*; D002648:Child; D002656:Child Day Care Centers; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000627:therapeutic use*; D006801:Humans; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000517:prevention & control*; D011174:Portugal / Q000453:epidemiology; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000145:classification / Q000302:isolation & purification*; D014611:Vaccination / Q000706:statistics & numerical data*; D018074:Vaccines, Conjugate / Q000627:therapeutic use
chemical_list: D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D018074:Vaccines, Conjugate
keywords: Antimicrobial resistance; Carriage; Children; Pneumococcal conjugate vaccine; Serotype; Streptococcus pneumoniae