%0 Journal Article
%T Heterogeneity of pneumococcal phase variants in invasive human infections
%A I Serrano
%A J Melo-Cristino
%A M Ramirez
%J BMC Microbiology
%D 2006
%I BioMed Central
%R 10.1186/1471-2180-6-67
%X We report the colony opacity phenotypes of a genetically diverse set of 304 invasive isolates representing 10 serotypes. Over half of the isolates (52%) presented the opaque phenotype whereas transparent variants accounted for only 26% of the total. However, the frequency of recovery of each phase variant was not uniform, while serotypes 1, 4, 12B and 23F presented the opaque phenotype more frequently than expected by chance, serotypes 3 and 14 where less frequently associated with this phenotype.The opaque phenotype was the most frequent phenotype found among invasive isolates. An unexpected and equally important finding is the variability of the dominant opacity phenotype found among serotypes. This observation highlights the heterogeneity of opacity phenotypes in invasive isolates and lends further support to the proposal that other factors, in addition to the site of isolation, determine the opacity phenotype of a given isolate. The association between serotype and colonial opacity could help explain epidemiological differences observed among pneumococcal serotypes such as a higher invasive disease potential.The only habitat identified for Streptococcus pneumoniae (pneumococcus) is the human host where the bacterium is able to persist and multiply, either asymptomatically in the mucosal surface of the nasopharynx or being responsible for infections that range from milder manifestations such as otitis media to life threatening infections such as bacteremia. The transition between the mucosal surface and the blood, two very different habitats, is thought to lead to changes in the physiology of the bacterium and its surface components. Recently, a phenomenon of intrastrain phase variation in the colonial opacity of the pneumococcus has been identified and related to increased survival in each of these habitats [1]. Studies on animal models revealed that the transparent variants (T) persist in the nasopharynx in vivo and show greater adherence in vitro to human phar
%U http://www.biomedcentral.com/1471-2180/6/67