목적: The purpose of this study was to evaluate the anti-biofilm effect of pyrimidine-diones against Streptococcus pneumoniae biofilm. 방법:S. pneumoniae D-39 strain (NCTC 7466) was obtained from the Health Protection Agency Culture Collections (HPA, Salisbury, UK). Effect of pyrimidine-diones on in-vitro biofilm growth was evaluated by time and dose dependent manner using microplate assay and cfu counting. Effect of pyrimidine-diones on already established biofilms was evaluated using confocal microscopy and scanning electron microscope (SEM). 결과:Pyrimidine-diones inhibited pneumococcal in-vitro biofilm growth. A significantly decreased biofilms biomasses and cfu counts were detected in the samples grown with pyrimidine-diones. The inhibitory effect of pyrimidine-diones was concentration and time dependent. However, the optical density and cfu counts of planktonic cells grown with pyrimidine-diones were not significantly decreased.The results of biofilm quantification of pre-established biofilm treated with different concentrations of pyrimidine-diones demonstrated no significant decrease in biofilm biomasses. The cfu counts were carried out only for control, 1uM and 10uM also demonstrated no difference in cfu counts. This indicates that pyrimidine-diones were unable to dismantle and kill the bacteria with in biofilms and hence do not possess biofilm eradication property.The conifocal microscopy analysis revealed a significant different morphology of biofilms growth with pyrimidine-diones in compare to control. The biofilms grown with pyrimidine-diones were thin, and the cells were scared and attached to the bottom of disc and the organized 3- dimensional structure were absent on confocal microscopy. 결론:Pyrimidine-diones showed inhibitory effect against biofilm formation, but not against established biofilm.