Oropharyngeal colonisation by groupA streptococci in Portugal: an eight-year surveillance study (20002007)

Abstract number: P1729

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

Objectives: To evaluate trends of oropharyngeal colonisation (OC) by Group A streptococci (GAS) and to assess the clonal structure of sporadic and persistent strains.

Methods: During 16 periods in 2000–07, oropharyngeal samples were taken from different populations: 6965 from children (0–6 yrs) in day-care centres (DCC), 2337 from school-aged children (7–16 yrs) and 1276 from adults (1169 school staff and 107 family members). Bacterial identification was carried out by standard methods. Resistance to erythromycin (E) and clindamycin (Da) was evaluated by disk diffusion and minimal inhibitory concentrations using E-tests. Clones of all resistant and a subset of susceptible isolates were defined by pulsed-field gel electrophoresis (PFGE) and further characterised by serotyping for T antigen (T-typing), and by sequencing for assignment of emm-types and multilocus sequence types (ST).

Results: A total of 1026 GAS were isolated. OC in younger children was higher (11.6%) than among older than 7 yrs (7.8%), and in adults was higher among family members (8.4%) than among school staff (2.6%). OC rates varied with DCC (min. 0%; max. 49%). Higher OC rates (>10%) were usually detected during winter periods (17% in 2001, 13% in 2002/03, 12% in 2007), and occasionally, during autumn of 2003 (15%) and spring of 2001 and 2004 (15% and 18%, respectively). E resistance was 10% in 2000–02, 28% in 2003, 20% in 2004, 3% in 2005, 14% in 2006 and 10% in 2007. Da resistance was lower than 10%, except in 2006 (14%). Six out of 98 PFGE types accounted for 49% of isolates studied (n = 380/775) which were included in five ST or lineages: ST36 (T12/emm12/PFGE.AB;PFGE.AP) (n = 172, mainly E susceptible); ST28 (T1/emm1/PFGE.X) (n = 87, all E susceptible); ST406 (T3.13.B3264/emm3/PFGE.BG) (n = 48, all E susceptible); ST382 (T6/emm6/PFGE.AD) (n = 38, all E susceptible); and ST39 (T4/emm4/PFGE.CZ) (n = 35, all E resistant). Three lineages and four PFGE types prevailed during peaks of OC: ST406 (PFGE.BG) in 2001 (winter and spring); ST36 (PFGE.AB) in 2002 (winter) and 2003 (autumn); ST36 (PFGE.AP) in 2003 (winter); and ST28 (PFGE.X) in 2004 (spring).

Conclusions: The GAS carrier state was seasonal and variable with age and DCC attendance. A very heterogeneous population of GAS colonised healthy carriers during 2000–07. However, some lineages/clones either resistant or susceptible to macrolides were identified as putative poor colonisers and others as widely disseminated and persistent over time.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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