Antibiotic resistance rates and macrolide resistance phenotypes of viridans group streptococci from the oropharynx of healthy Greek children

A total of 200 isolates of viridans group streptococci isolated from the oropharynx of healthy Greek children were studied. Vancomycin, rifampicin, fluoroquinolones and dalfopristin/quinupristin were active against all tested isolates. High level resistance to gentamicin was not seen. Intermediate and high-level penicillin resistance was present in 28.5 and 14.5% isolates, respectively, with 41.3% of the latter group, being also resistant to cefotaxime. Resistance rates to other antimicrobials were as follows - erythromycin 38.5%, clarithromycin 33.5%, clindamycin 7.5% and tetracycline 23%. Penicillin resistance occurred more frequently in Streptococcus mitis isolates, while macrolide resistance was more frequent in S. oralis. MLSB resistance phenotype M was dominant (74%) among erythromycin resistant isolates, with phenotypes IR and CR being represented by 6 and 20% of isolates, respectively.