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In vitro susceptibility of respiratory isolates of Streptococcus pneumoniae and Streptococcus pyogenes in a twelve-month period

Abstract number: P1749

Popescu G.A., Benea E., Popescu C., Popoiu M., Furtuna M., Antonica D., Ivan M., Botea S., Streinu-Cercel A.

Therapy is often empirical in respiratory tract infections and there is a need for local data on the rate of resistance to available antimicrobials. Increased levels of macrolide-resistant Streptococcus pyogenes and Streptococcus pneumoniae in several regions have been reported.

Objective: To study the antimicrobial susceptibility of two major pathogens: Streptococcus pneumoniae and Streptococcus pyogenes, to define the place of several alternative regimens in the first line therapy for pharyngitis and lower respiratory tract infection.

Methods: Antimicrobial susceptibility tests analysis for a total of 232 unique isolates of Streptococcus pyogenes and 107 isolates of Streptococcus pneumoniae recovered between December 2006 and November 2007 at the National Matei Bals Infectious Diseases Institute, Bucharest, as a part of the MART surveillance study. Antibiotic susceptibilities were determined with disk diffusion method and confirmed with E-tests for penicillin.

Results:S. pyogenes isolates were uniformly susceptible to b-lactams, sulfamethoxazole/trimethoprim and vancomycin; macrolide-resistance was noted for 6.55% of strains (9 strains with M phenotype and 6 strains with MLSB resistance). Three isolates were resistant to levofloxacin (1.4%), all macrolide-susceptible, and six isolates resistant to tetracycline (5.3%), two of them macrolide-resistant ones. S. pneumoniae strains were uniformly susceptible for moxifloxacin, vancomycin and linezolid; diminished susceptibility to penicillin was noted for 57.1% strains, macrolide-resistance for 47.2% strains (two thirds with MLSB phenotype) and multiresistance for 43.9% strains. Susceptibility of penicillin-resistant strains was: 96.3% for rifampin, 85.5% for cloramphenicol, 80% for tetracycline, 44% for clindamycin. Susceptibility of macrolide resistant strains were: rifampine 98.7%, ceftriaxone 62.6%, tetracycline 21%.

Conclusion: Macrolide-resistance is yet at low level for S. pyogenes, but higher for S. pneumoniae, probably due to increased consumption of macrolides. The risk of selective pressure with continuous rise of macrolide-resistance whatever it is the indication for usage, could impose a restricted access, especially in outpatient pharyngitis or respiratory infections. A similar situation could be defined for sulfamethoxazole/trimethoprim; concerning doxycycline, is possible that breakpoints are too high and/or defined daily dose too low for pneumococcal infections.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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