title: Carriage of Haemophilus influenzae is associated with pneumococcal vaccination in Italian children.
abstract: BACKGROUND
  The pneumococcal population changes observed after the implementation of children immunization with pneumococcal conjugative vaccines (PCV) might have affected the composition of the microbial flora inhabiting the same ecological niche of Streptococcus pneumoniae. The aim of this study was to investigate the effect of PCV immunization, (PCV7 or PCV13), on S. pneumoniae and Haemophilus influenzae colonization in young children in Italy.
  
  
  METHODS
  Nasopharyngeal swabs were obtained from 301 children under 6 years of age (vaccinated or unvaccinated with PCV) during the period January-April 2012. Presence of S. pneumoniae and H. influenzae was investigated using conventional cultural methods. S. pneumoniae isolates were serotyped by the Quellung reaction; capsular type of H. influenzae isolates was determined by PCR. The pattern of associations between the two species and potential risk factors were investigated by a Structural Equation Modelling (SEM) analysis.
  
  
  RESULTS
  The prevalence of carriage was 31.56% and 43.18% for S. pneumoniae and H. influenzae, respectively. The majority of S. pneumoniae isolates belonged to non vaccine serotypes (non PCV13-types 81.1%) while H. influenzae isolates were all non-typeable. SEM analysis revealed a synergistic association between S. pneumoniae and H. influenzae colonization (rho: 0.27; 95%CI: 0.09-0.46; p=0.004). In addition, children vaccinated with PCV, either with PCV7 (coef 0.43; 95%CI: 0.07-0.79; p=0.021) or with PCV13 (coef: 0.45; 95%CI: 0.08-0.82; p=0.018), were more likely to be colonized by H. influenzae.
  
  
  CONCLUSIONS
  Pneumococcal vaccination increased H. influenzae nasopharyngeal carriage in children. This result highlights that an indirect effect of PCV vaccination can be perturbation of the nasopharyngeal flora. In the era of higher-valent pneumococcal vaccines, surveillance of carriage is crucial to monitor alterations in the bacterial ecosystem, thus preventing possible clinical problems.
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Romina
authors.initials: R
authors.lastname: Camilli
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Maria Fenicia
authors.initials: MF
authors.lastname: Vescio
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Giufrè
authors.affiliation: Unit of Microbiology, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Daprai
authors.affiliation: Unit of Microbiology, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Garlaschi
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Cerquetti
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy. Electronic address: annalisa.pantosti@iss.it.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Pantosti
mesh_terms: D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D006192:Haemophilus Infections / Q000453:epidemiology*; D006193:Haemophilus influenzae / Q000302:isolation & purification*; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000008:administration & dosage*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007558:Italy / Q000453:epidemiology; D008297:Male; D009305:Nasopharynx / Q000382:microbiology; D011008:Pneumococcal Infections / Q000453:epidemiology; D022242:Pneumococcal Vaccines / Q000008:administration & dosage*; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000302:isolation & purification; D014611:Vaccination / Q000706:statistics & numerical data
chemical_list: C538862:13-valent pneumococcal vaccine; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines
keywords: Haemophilus influenzae; Nasopharyngeal carriage; PCV13; PCV7; Streptococcus pneumoniae