Molecular characterisation of Streptococcus pneumoniae strains isolated from children with acute otitis media in Barcelona (1992–2005)

Abstract number: 1733_497

Ardanuy C., Gené A., Calatayud L., Palacín E., Fenoll A., Liñares J.

Objectives:S. pneumoniae (Spn) is a frequent cause of acute otitis media (AOM) in children. The aims of this study were: (a) To analyse the distribution of Spn clones causing AOM in children in Barcelona (1992–2005). (b) To analyse the impact of the heptavalent pneumococcal conjugated vaccine (PCV7).

Methods: Three hundred and twenty pneumococci isolated from children (1992–2005) with AOM were studied. Serotyping was performed by Quellung reaction. The antibiotic susceptibility was performed by agar dilution and disk-diffusion methods to penicillin (PEN), erythromycin, clindamycin, tetracycline, chloramphenicol and cotrimoxazole. The isolates were typed by PFGE (SmaI and/or ApaI). Representative isolates of each dominant clone were studied by MLST.

Results: The most frequent serogroups were: 19 (31%), 6 (23%), 14 (14%), 23 (11%) and 3 (6%). Among 300 pneumococci studied by PFGE, 114 different band patterns were found. Four multiresistant clones, Spain6B-2 (14%), Spain9V-3 (12%), clone ST88 of serotype 19F (9%) and Spain23F-1 (9%) accounted for 44% of strains. Among 221 PEN-R Spn, 66 different PFGE patterns were found. Eight of them (Spain6B-2, Spain9V-3, ST88 clone of serotype 19F, Spain23F-1, Sweden15A-25, Spain14–5, Poland6B-20, and ST276 clone of serotype 19A) accounted for 73.7% of PEN-R strains. Among 79 PEN-S strains, 52 PFGE patterns were found, 39 (49%) of them had a single isolate. Multidrug-resistance was observed in 81% of PEN-R strains and 17% of PEN-S strains (p < 0.001). Capsular switching was observed in three clones: Spain9V-3 (25/36 were serotype 14 and 1/36 was serogroup 19); Spain23F-1 clone (3/26 were serogroup 19); Sweden15A-25 clone (10/13 were serogroup 19 and 1/13 was serotype 23F). Comparing 1996–2000 and 2001–2005 periods the following changes were observed: (1) A decrease in the rate of PEN-R isolates (76% vs 61%). (2) A decrease in the vaccine serotypes (6B, 14, 23F). (3) An increase in the vaccine-related serotype 19A. (4) A significant decrease of Spain6B-2 clone (17% vs 4%), Spain23F-1 clone (11.0 vs 1.3) and ST88 clone of serotype 19F (9% vs. 4%) observed. (5) The emergence of a new clone related to serotype 19A (ST276) (0% vs 5%).

Conclusion: The proportion of episodes of AOM caused by PEN-R Spn decreased after the introduction of the PCV7 in Barcelona, coinciding with a decrease of multiR clones of vaccine related serotypes. Capsular switching was frequently observed.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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