ABSTRACT

This experiment investigated the effectiveness of using G. chinensis to inhibit the growth of Gram-negative vs. Gram-positive biofilms. It was hypothesized that if biofilms of both Gram-types were to be exposed to G. chinensis water extract, then Gram-positive biofilm formation would be inhibited more than Gram-negative biofilm formation. Gram-negative E. coli and Gram-positive M. luteus biofilms exposed to different concentrations of G. chinensis extract were grown in 96-well plates and quantified using the crystal violet assay. Biofilm formation of samples exposed to G. chinensis extract was determined relative to biofilm formation of control samples that were not exposed to treatment. At extract concentrations of 0.005 mg/ml, 0.01 mg/ml, 0.02 mg/ml, 0.04 mg/ml, and 0.08 mg/ml, biofilm formation was not strongly inhibited in either species. At extract concentrations of 0.16 mg/ml, 0.32 mg/ml, 0.64 mg/ml, and 0.128 mg/ml, biofilm formation was more significantly inhibited in both species. E. coli biofilm formation reached its lowest at a concentration of 0.32 mg/ml, with a relative biofilm formation of between 0.4 and 0.5. M. luteus biofilm formation decreased with increasing extract concentration, reaching its lowest at a concentration of 0.128 mg/ml, with a relative biofilm formation of between 0.2 and 0.3. The lower amount of biofilm formation observed for M. luteus indicated that exposure to G. chinensis had a stronger inhibitory effect on the biofilm formation of M. luteus than that of E. coli. This suggests that a higher extract concentration is required to treat Gram-negative biofilms than Gram-positive biofilms.