The aim of this study was to develop a new selective medium for isolation of Streptococcus anginosus group (SAG) strains, by adding sulphamethazine and aztreonam as selective agents at Mitis-Salivarius agar (MSA), the medium commonly used for recovery of oral streptococci from oral samples.
Material and method: The evaluation of Mitis-Salivarius--sulphamethazine--aztreonam agar (MSSAA) for SAG selectivity was performed by testing the growth of type strains and laboratory-stored clinical isolates of different oral streptococcal species on this medium and also by investigating the SAG recovery on MSSAA in comparison with MSA and the growth inhibition of non-SAG strains from 100 saliva and 11 pus samples (collected from healthy young subjects and from paediatric patients with upper respiratory tract infections, respectively) on MSSAA.
Results: The same SAG recovery rate was obtained on both MSSAA and MSA, while non-SAG strains failed to grow on the novel medium, except for enterococci. The results of the present study have indicated that MSSAA is a suitable medium for selecting SAG isolates from clinical specimens.