Journal Article

Emergence of invasive erythromycin-resistant <i>Streptococcus pneumoniae</i> strains in Portugal: contribution and phylogenetic relatedness of serotype 14

Ricardo Dias and Manuela Caniça

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 54, issue 6, pages 1035-1039
Published in print December 2004 | ISSN: 0305-7453
Published online December 2004 | e-ISSN: 1460-2091 | DOI:
Emergence of invasive erythromycin-resistant Streptococcus pneumoniae strains in Portugal: contribution and phylogenetic relatedness of serotype 14

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  • Medical Oncology
  • Critical Care


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Objectives: To study the phenotype and phylogenetic relatedness of invasive Streptococcus pneumoniae strains isolated in Portugal.

Methods: A total of 614 invasive S. pneumoniae strains, isolated in Portugal from 1999 to the first 6 months of 2002, were characterized using serotyping and antimicrobial susceptibility testing. National outpatient sale data for macrolides were compared with erythromycin resistance. We investigated the main clonal lineages from erythromycin-resistant strains of serotype 14 by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST).

Results: The emergence of erythromycin-resistant strains correlated well with the usage of azithromycin in Portugal during the period of the study (r=0.900, P=0.001). Serotype 14 made the largest contribution to this emergence. We found two clonal complexes (CC) among erythromycin-resistant strains: CC1 was formed by three sequence types (ST), ST156, ST143 and ST1042, and CC2 by ST15 and ST9. All STs described, except ST1042, are putative founders of clonal groups or subgroups from serotype 14 as defined in the pneumococcal MLST database.

Conclusions: This study suggests that macrolides usage is an important factor enhancing the spread of invasive erythromycin-resistant S. pneumoniae clones in Portugal. The study also makes a contribution to the understanding of spread of erythromycin-resistant clones in an international context.

Keywords: pneumococci; macrolide resistance; pulsed-field gel electrophoresis; multilocus sequence typing; international clones

Journal Article.  2335 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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