In vitro antibiotic susceptibility of anginosus group streptococci strains isolated from oral and respiratory tract infections

Abstract number: R2116

Bancescu G., Nistor I., Bancescu A., Andrei M., Barbuceanu S., Topolniski M.A.

Objectives: The streptococci of anginosus group belong to the normal flora of the oral cavity, upper respiratory tract, gastrointestinal tract and urogenital tract. However, these streptococci are often involved in the aetiology of different pyogenic infections. The aim of the present study was to investigate the susceptibility of anginosus streptococci strains (isolated either in pure culture or in association with other microorganisms, especially anaerobic bacteria) from pus samples collected from Romanian patients with different oral and respiratory tract infections (mostly oral abscesses and sinusitis).

Methods: The identification of the Streptococcus anginosus group isolates at the species level was done using the Rapid ID 32 STREP system (Bio-Mérieux, France) and some additional biochemical tests. The investigation of the susceptibility of the isolates to: penicillin G, amoxicillin, erythromycin, clindamycin, chloramphenicol and tetracycline was performed by the Etest (AB Biodisk, Solna, Sweden). The phenotype of erythromycin resistance was detected using the double disk diffusion test.

Results: The anginosus group isolates belonged to: S. anginosus – which predominated (70% of the strains), S. constellatus and S. intermedius species. The MICs values varied between: 0.002–0.75 mg/l for penicillin G, 0.016–0.5 mg/l for amoxicillin, 0.016–4 mg/l for erythromycin, 0.016–0.047 mg/l for clindamycin, 0.016–4 mg/l for chloramphenicol and 0.047–256 mg/l for tetracycline. Reduced susceptibility to b-lactam antibiotics was found among the strains belonging to S. constellatus species. About 10% of the strains were resistant to erythromycin and only the M phenotype was established. Almost half of the total number of the isolates were resistant to tetracycline.

Conclusions: The results indicated that the susceptibility of the oral streptococci isolates of clinical importance should be periodically tested, mainly to the widely-used antibiotics. Clindamycin was fully active (as chloramphenicol) and might represent a therapeutical alternative for patients allergic to b-lactam antibiotics, while tetracycline is not recommended in infections in which oral streptococci are involved. Due to their role in human pathology, the anginosus group streptococci merit to be identified at species level in clinical laboratory.

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:
Back to top