Characteristics of longitudinal oropharyngeal asymptomatic colonization and of multicolonizaton by different strains of groupA streptococci from Portugal

Abstract number: P1047

Pires R., Alves C., Esteves F., Rolo D., Almeida J.M.F., Ramos T., Gameiro C., Andrade F., Lopes A., Romeiro L., Vaz F., Morais A., Brito-Avô A., Gonçalo-Marques J., Santos-Sanches I.

Objective: To examine the long-term asymptomatic oropharyngeal colonization status by Group A streptococci (GAS) and if co-colonization of the oropharynx by multiple GAS strains occurs among asymptomatic persons.

Methods: Between 2000 and 2004, 5,494 oropharyngeal samples were taken during 12 sampling periods in October, February and May of each year from 1,729 healthy individuals. Bacterial identification was carried out by standard methods. The total number of GAS isolates was 626 (carriage rate 11.4%) out of which 243 (38.8%) were from 113 (6.5%) recurrent carriers – defined as colonized by GAS more than once during 2 to 12 sampling periods. These isolates were considered as associated with long-term or longitudinal colonization. All b-hemolytic colonies identified as GAS that were picked from each of the primary plates containing the swabs of 23 participants, out of 865 (2.7%) persons sampled in one sampling period, were considered as causing co-colonization or multicolonization of the same niche. Isolates of both groups – 243 causing longitudinal colonization and 74 isolates causing multicolonizaton – were typed by pulsed-field gel electrophoresis (PFGE) for strain definition and by sequencing part of the emm gene encoding the M surface protein (emm typing).

Results: Of the 113 recurrent carriers, 111 were colonized in 2 or 3 sampling periods and 2 were colonized in 4 sampling periods. In the majority of the recurrent carriers (n = 89, 78.8%), strain replacement was observed. Examples that occurred frequently were emm12 (PFGE.AB) replaced by emm1 (PFGE.X) or emm3 (PFGE.BG), and emm1 (PFGE.X) replaced by emm12 (PFGE.AP). The remaining 24 (21.2%) persons were carriers of a same strain. Also, out of the 113 persons, 54 (47.8%) were carriers at least once of emm12 strains. Of the 23 participants of the multicolonization study, 6 (26.1%) were colonized by multiple strains of different PFGE types and of a same emm type. An example was one individual that carried 3 emm75 strains (PFGE.CY, PFGE.FM and PFGE.FN types).

Conclusions: A replacement of GAS strains was frequently found among recurrent carriers and co-colonization of the oropharynx by multiple GAS strains was detected. emm12 isolates seem to be successful colonizers as they were identified as widely disseminated among epidemiological related and unrelated carriers and were persistent overtime.

Session Details

Date: 10/04/2010
Time: 00:00-00:00
Session name: Abstracts 20th European Congress of Clinical Microbiology and Infectious Diseases
Location: Vienna, Austria, 10 - 13 April 2010
Presentation type:
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