title: Serotype distribution and antimicrobial susceptibilities of nasopharyngeal isolates of Streptococcus pneumoniae from healthy children in the 13-valent pneumococcal conjugate vaccine era.
abstract: Few epidemiological data are available since the introduction of 13-valent pneumococcal vaccine (PCV13) in 2010. We conducted a cross-sectional study to estimate the prevalence of Streptococcus pneumoniae (SP) nasopharyngeal carriage in healthy Italian infants and young children and to evaluate the impact of PCV13 on pneumococcal colonization. In the trimester September-December 2011 nasopharyngeal swabs were collected from healthy children aged 3-59 months presenting for routine well careat 16 primary care pediatricians in Milan. SP carriage isolates were serotyped and tested for antimicrobial resistance using EUCAST breakpoints. Among 1250 enrolled children, 618 had received at least 1 dose of PCV13, 292 at least 1 dose of PCV7, 94 a combination of the two vaccines and 246 were not vaccinated. The prevalence of SP carriage was 27% (95% confidence interval [CI] 25-30). At multivariable analysis, age≥25 months (prevalence ratio [PR]=0.74) and use of antibiotics in the previous 3 months (PR=0.67) were associated with lower SP carriage prevalence. Having siblings (PR=1.79 for 1 sibling and PR=2.23 for ≥2 siblings), day-care attendance (PR=2.27) and respiratory tract infections in the previous 3 months (PR=1.39) were associated with higher SP carriage prevalence. The immunization status for SP was not associated with SP carriage at univariable or at multivariable analysis. The most common carriage isolates were 6C, 19A and 23A. The prevalence of the six additional PCV13 serotypes carriage in children appropriately vaccinated with PCV13 was lower than in children appropriately vaccinated with PCV7 (0 vs. 0.060); the greater reduction in prevalence of carriage was observed for serotype 19A (0 vs. 0.041). Serotype 6C was the most common drug-resistant serotype (17.2%). Further epidemiological studies are needed to assess changes in circulating SP serotypes following the large-scale introduction of PCV13.
authors.affiliation: Department of Paediatrics, L. Sacco Hospital, University of Milan, Italy. Electronic address: gianvincenzo.zuccotti@unimi.it.
authors.forename: Gianvincenzo
authors.initials: G
authors.lastname: Zuccotti
authors.affiliation: Department of Paediatrics, L. Sacco Hospital, University of Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Mameli
authors.affiliation: Microbiology Laboratory, Policlinico, Cà Granda Ospedale Maggiore Foundation, Milan, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Daprai
authors.affiliation: Microbiology Laboratory, Policlinico, Cà Granda Ospedale Maggiore Foundation, Milan, Italy.
authors.forename: Maria Laura
authors.initials: ML
authors.lastname: Garlaschi
authors.affiliation: Department of Paediatrics, L. Sacco Hospital, University of Milan, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Dilillo
authors.affiliation: Clinical Epidemiology Unit, Liver Research Center, Trieste, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bedogni
authors.affiliation: Prevention Department, Local Health Authority, Milan, Italy.
authors.forename: Marino
authors.initials: M
authors.lastname: Faccini
authors.affiliation: Unità Organizzativa Governo della prevenzione e tutela sanitaria, Direzione Generale Sanità, Regione Lombardia, Milan, Italy.
authors.forename: Maria
authors.initials: M
authors.lastname: Gramegna
authors.affiliation: Microbiology Laboratory, Policlinico, Cà Granda Ospedale Maggiore Foundation, Milan, Italy.
authors.forename: Erminio
authors.initials: E
authors.lastname: Torresani
authors.forename: Emanuela
authors.initials: E
authors.lastname: Ballerini
authors.forename: Annarita
authors.initials: A
authors.lastname: Benincaso
authors.forename: Milena
authors.initials: M
authors.lastname: Bonvissuto
authors.forename: Dorella
authors.initials: D
authors.lastname: Bricalli
authors.forename: Manuela
authors.initials: M
authors.lastname: Brioschi
authors.forename: Cinzia Simona
authors.initials: CS
authors.lastname: Calloni
authors.forename: Marina Irene
authors.initials: MI
authors.lastname: Camiletti
authors.forename: Giacomo
authors.initials: G
authors.lastname: Colella
authors.forename: Laura
authors.initials: L
authors.lastname: De Angelis
authors.forename: Silvia
authors.initials: S
authors.lastname: Decarlis
authors.forename: Francesca
authors.initials: F
authors.lastname: Di Nello
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Dozzi
authors.forename: Erica
authors.initials: E
authors.lastname: Galli
authors.forename: Vera
authors.initials: V
authors.lastname: Gandini
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Giuliani
authors.forename: Franca
authors.initials: F
authors.lastname: Laviola
authors.forename: Barbara
authors.initials: B
authors.lastname: Loda
authors.forename: Maddalena
authors.initials: M
authors.lastname: Macedoni
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Mazzucchi
authors.forename: Maria Gabriella
authors.initials: MG
authors.lastname: Metta
authors.forename: Anna
authors.initials: A
authors.lastname: Moscatiello
authors.forename: Pilar
authors.initials: P
authors.lastname: Nannini
authors.forename: Mariangela
authors.initials: M
authors.lastname: Petruzzi
authors.forename: Damiano
authors.initials: D
authors.lastname: Picicco
authors.forename: Michela
authors.initials: M
authors.lastname: Picciotti
authors.forename: Stefania
authors.initials: S
authors.lastname: Pisanelli
authors.forename: Norberto
authors.initials: N
authors.lastname: Porta
authors.forename: Giulia
authors.initials: G
authors.lastname: Ramponi
authors.forename: Francesca
authors.initials: F
authors.lastname: Redaelli
authors.forename: Riccardo
authors.initials: R
authors.lastname: Rubini
authors.forename: Natascia
authors.initials: N
authors.lastname: Sala
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Saitta
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Scelza
authors.forename: Rosa Maria
authors.initials: RM
authors.lastname: Tiso
authors.forename: Mariangela
authors.initials: M
authors.lastname: Tomasetto
authors.forename: Matteo
authors.initials: M
authors.lastname: Torcoletti
authors.forename: Marta
authors.initials: M
authors.lastname: Travaini
authors.forename: Maurizio
authors.initials: M
authors.lastname: Valentini
authors.forename: Chiara
authors.initials: C
authors.lastname: Vessia
mesh_terms: D002353:Carrier State / Q000382:microbiology*; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D007223:Infant; D007558:Italy; D008297:Male; D008826:Microbial Sensitivity Tests; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification
chemical_list: C538862:13-valent pneumococcal vaccine; D022242:Pneumococcal Vaccines
keywords: 13-Valent pneumococcal conjugate vaccine; CI; Children; IPD; MDR; MIC; NC; NVS; PCV13; PCV7; PR; Pneumococcal nasopharyngeal carriage; SP; Streptococcus pneumoniae; confidence interval; invasive pneumococcal diseases; minimal inhibitory concentration; multidrug resistance; nasopharyngeal carriage; non vaccine serotypes; pneumococcal 13-valent vaccine; pneumococcal 7-valent vaccine; prevalence ratio