Pneumococcal carriage in children attending a hospital outpatient clinic in the era of pneumococcal conjugate vaccines in Barcelona

Between April 2004 and March 2006 an oropharyngeal swab was obtained from 502 asymptomatic children, aged 6 months to 6 years, at a tertiary children's hospital outpatient department to assess the pneumococcal colonisation rate, risk factors, serotype distribution and antimicrobial susceptibility. Only 126 (25.3%) children had received ≥ 1 dose of PCV7. The pneumococcal carriage rate was 23.5%. Carrier rates were significantly higher in children aged ≥ 24 months and children attending daycare center. Thirty six (31.0%) of the isolates were contained in PCV7, 39 (33.6%) in PCV10 and 62 (53.4%) in PCV13. Forty-four strains (37.9%) were resistant to penicillin. Vaccine serotype (VT) strains were more likely to be penicillin-nonsusceptible S. pneumoniae than non-PCV7 serotype (NVT) strains (66.7% vs. 21.6%; P < 0.001). In our pediatric population, NVT were predominant among pneumococcal carriers whereas antibiotic resistance was significantly associated with VT. PCV13 can substantially increase the serotype coverage of S.pneumoniae in healthy carriers.