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Journal of Clinical Microbiology, August 2008, p. 2508-2518, Vol. 46, No. 8
0095-1137/08/$08.00+0     doi:10.1128/JCM.02296-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Phenotypic and Genotypic Characterization of Streptococcus pneumoniae Strains Colonizing Children Attending Day-Care Centers in Norway{triangledown}

Didrik F. Vestrheim, E. Arne Høiby, Ingeborg S. Aaberge, and Dominique A. Caugant*

Department of Bacteriology and Immunology, Division of Infectious Disease Control, Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, NO-0403 Oslo, Norway

Received 29 November 2007/ Returned for modification 7 December 2007/ Accepted 21 May 2008

A cross-sectional study of nasopharyngeal colonization with Streptococcus pneumoniae was performed among 573 children attending 29 day-care centers (DCCs) in Norway prior to the start of mass vaccination with the heptavalent pneumococcal conjugate vaccine (PCV-7). A sensitive sampling method was employed, including transport in an enrichment broth and serotyping of pneumococci directly from the broth, in addition to traditional single-colony isolation from blood agar plates. The prevalence of carriage was high, peaking at 88.7% in 2-year-olds. More than one serotype was isolated from 12.7% of the carriers. Of 509 isolates obtained, 227 (44.6%) belonged to the PCV-7 serotypes. Penicillin nonsusceptibility was rare (1.8% of the isolates). Nonsusceptibility to erythromycin (5.9%), clindamycin (2.0%), and tetracycline (5.5%) was associated with PCV-7 serotypes (P < 0.001). Multilocus sequence typing was performed on the whole strain collection, revealing 102 sequence types (STs), of which 31 (30.4%) were novel. Eleven isolates (2.2%) belonged to the England14-9 clone, and 19 isolates (3.7%) belonged to, or were single-locus variants of, the Portugal19F-21 clone. The pneumococcal populations within the DCCs were composed of a majority of isolates with STs shared between the DCCs and a minority of isolates with STs unique for each DCC. The highest numbers of different STs, including novel STs, were found within the most frequent serotypes. Our study indicates that carriage of S. pneumoniae is highly prevalent among children in Norwegian DCCs, with a genetically diverse pneumococcal population consisting of unique microepidemic DCC populations.

* Corresponding author. Mailing address: Department of Bacteriology and Immunology, Division of Infectious Disease Control, Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, N-0403 Oslo, Norway. Phone: 47 21 07 63 11. Fax: 47 21 07 65 18. E-mail: dominique.caugant{at}fhi.no

{triangledown} Published ahead of print on 4 June 2008.

Journal of Clinical Microbiology, August 2008, p. 2508-2518, Vol. 46, No. 8
0095-1137/08/$08.00+0     doi:10.1128/JCM.02296-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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