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Antimicrobial resistance trends in haemolytic streptococci from throat infections in a paediatric hospital in Greece

Abstract number: P1485

Giannakopoulou K., Antonaki G., Paleologou N., Kallimani A., Margoni A., Christopoulos S., Lebessi E.

Objectives: To evaluate the antimicrobial susceptibilities and macrolide – resistance phenotypes of large-colony-forming b-haemolytic streptococci (BHS) isolated from throat infections at a pediatric population in the area of Athens.

Methods: All BHS isolated from 7710 pharyngeal specimens obtained from patients referred to "P. & A. Kyriakou" Children's Hospital over a five-year period (Jan 2004 through Dec 2008) were reviewed using the laboratory archives. Streptococcus agalactiae isolates were not included. Susceptibility testing to penicillin, erythromycin, clindamycin, tetracycline, chloramphenicol, cefotaxime, rifampin and vancomycin was performed by disk diffusion test according to the CLSI guidelines. Macrolide resistance phenotypes were determined for strains isolated during 2006 to 2008, by double-disk diffusion test using erythromycin and clindamycin.

Results: During the study period a total of 1908 BHS were isolated. Of these, Streptococcus pyogenes was accounted for 95.2% (1817/1908) and Streptococcus dysgalactiae subsp. equisimilis (Lancefield group C, G) for 4.8% (91/1908). Among S. pyogenes isolates, resistance to erythromycin was found in 19% (annual resistance rates from 2004 to 2008: 13.1%, 15.8%, 21%, 19.8%, 26%), resistance to chloramphenicol and tetracyline was found in 0.4% and 7.9%, respectively. Sixty seven percent of tetracycline resistant strains were also resistant to erythromycin. Among S. dysgalactiae subsp. equisimilis isolates, higher resistance rates to erythromycin, chloramphenicol and tetracycline were found to be 23.1%, 1.1%, and 37.3%, respectively. The macrolide-resistance phenotype distribution (2006 through 2008) was as follows: M; 44.4%, 55.5%, 32.4%, MLSBi; 33.3%, 22.2%, 44.5%, MLSBc; 22.2%, 22.2%, 22.9%. The prevalent phenotype of MLSB resistance in S. pyogenes isolates have been changed from the M to the MLSBi. Resistance to antimicrobial agents other than macrolides, clindamycin, tetracycline, and chloramphenicol was not found.

Conclusions: There was a progressive increase of resistance to macrolides and a relative decrease in the M phenotype. This reduces the effectiveness of macrolides and clindamycin as an alternative treatment. Continual monitoring of antimicrobial resistance among large-colony-forming BHS is very important for the option of the empiric therapy.

Session Details

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