title: Carriage of Haemophilus influenzae in the oropharynx of young children and molecular epidemiology of the isolates after fifteen years of H. influenzae type b vaccination in Italy.
abstract: BACKGROUND
  Haemophilus influenzae is an important pathogen able to cause a wide spectrum of diseases in children. Colonization of the upper respiratory tract is a risk factor for developing disease. This study aimed to investigate the oropharyngeal carriage rate of H. influenzae in young children in two Italian cities, 15 years after H. influenzae type b (Hib) vaccination was introduced. Antibiotic resistant traits and genotypes of the colonizing H. influenzae isolates were investigated.
  
  
  METHODS
  Oropharyngeal swabs were obtained from 717 healthy children aged <6 years (June 2012-July 2013). Potential risk factors for H. influenzae colonization were investigated. H. influenzae isolates from carriage were characterized by PCR capsular typing, ampicillin susceptibility testing, resistance-associated gene sequencing and multilocus sequence typing (MLST). For comparison purposes, 38 non-typeable H. influenzae (NTHi) isolates from invasive disease were genotyped by MLST.
  
  
  RESULTS
  The overall H. influenzae carriage rate was 14.1% (101/717). Age, study site, presence of young siblings, and complete Hib vaccination status were independently associated with colonization. Of 101 isolates, 98 were NTHi, 2 were type e and 1 was type f. The overall ampicillin resistance rate was 15.8% (16/101). Resistance was mediated by TEM-1 β-lactamase production in half of isolates (n=8) or modifications in penicillin-binding protein (PBP) 3 in the other half (n=8). Several substitutions were discovered in PBP3 including the Asn526Lys change. Seventy-six different STs were identified among 98 NTHi isolates from carriage, with only 4 STs (ST12, ST57, ST238, ST1238) encompassing ≥ 3 isolates. Comparison of carriage and disease isolates found that several STs were shared between the two sources, although none of the major disease-associated STs were observed in carriage isolates.
  
  
  CONCLUSIONS
  NTHi is the predominant serotype in carriage. The importance of monitoring both NTHi colonization rate and circulating genotypes should be emphasized in the era of the Hib conjugate vaccines.
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Giufrè
authors.affiliation: Unit of Microbiology, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Daprai
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome, Italy.
authors.forename: Rita
authors.initials: R
authors.lastname: Cardines
authors.affiliation: Unit of Microbiology, Bambino Gesù Children's Hospital, Rome, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Bernaschi
authors.affiliation: Unit of Clinical Epidemiology, Bambino Gesù Children's Hospital, Rome, Italy.
authors.forename: Lucilla
authors.initials: L
authors.lastname: Ravà
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome, Italy.
authors.forename: Marisa
authors.initials: M
authors.lastname: Accogli
authors.affiliation: Medical Direction, Bambino Gesù Children's Hospital, Rome, Italy.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Raponi
authors.affiliation: Unit of Microbiology, Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico, Milano, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Garlaschi
authors.affiliation: Medical Direction, Bambino Gesù Children's Hospital, Rome, Italy.
authors.forename: Marta Luisa
authors.initials: ML
authors.lastname: Ciofi degli Atti
authors.affiliation: Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, Rome, Italy. Electronic address: marina.cerquetti@iss.it.
authors.forename: Marina
authors.initials: M
authors.lastname: Cerquetti
mesh_terms: D002353:Carrier State / Q000453:epidemiology*; D002675:Child, Preschool; D002947:Cities / Q000453:epidemiology; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000517:prevention & control*; D018073:Haemophilus Vaccines / Q000008:administration & dosage*; D006193:Haemophilus influenzae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007558:Italy / Q000453:epidemiology; D008297:Male; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D009960:Oropharynx / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D018073:Haemophilus Vaccines
keywords: H. influenzae; MLST; Oropharyngeal carriage; ftsI; β-Lactam resistance