Beschreibung:
<jats:p>
<jats:named-content content-type="genus-species">Streptococcus pneumoniae</jats:named-content>
is a common resident in the human nasopharynx. However, carriage can result in severe diseases due to a unique repertoire of pathogenicity factors that are rare in closely related commensal streptococci. We investigated a penicillin-resistant
<jats:named-content content-type="genus-species">S. pneumoniae</jats:named-content>
clone of serotype 23F isolated from a cystic fibrosis patient on multiple occasions over an unusually long period of over 3 years that was present without causing disease. Genome comparisons revealed an apparent nonfunctional pneumococcus-specific gene encoding a hyaluronidase, supporting the view that this enzyme adds to the virulence potential of the bacterium. The 23F clone harbored unique mosaic genes encoding penicillin resistance determinants, the product of horizontal gene transfer involving the commensal
<jats:named-content content-type="genus-species">S. mitis</jats:named-content>
as donor species. Sequences identical to one such mosaic gene were identified in an
<jats:named-content content-type="genus-species">S. mitis</jats:named-content>
strain from the same patient, suggesting that in this case
<jats:named-content content-type="genus-species">S. pneumoniae</jats:named-content>
played the role of donor.
</jats:p>