FIG 4.
(a) Measurement of MRSA biofilm formation after 24 h in the presence of antimicrobial peptoids (AMPs) and conventional antibiotics. Prevention of biofilm formation is plotted as percent biomass analyzed by crystal violet assay. Data points are represented as means using three replicates. Error bars are represented as ± standard deviation (SD). Peptoid 1, Peptoid 1-11mer, and Peptoid 1-C134mer showed a significant change in biofilm formation compared to the no treatment control from 0.39 μM and upward. LL-37 showed significance starting at 0.78 μM while amoxicillin showed significance starting at 1.56 μM. Ciprofloxacin showed a significant increase in biofilm formation at 0.39 μM, however, showed a significant decrease at concentrations of 0.78 μM and up. (b) Measurement of MRSA biofilm detachment after 24 h by AMPs and conventional antibiotics. Detachment is plotted as percent biomass of established biofilms after treatment with antimicrobials. Data points are represented as means using three replicates. Error bars are represented as ± SD. Peptoid 1 showed significance compared to the no treatment control at concentrations of 0.78 μM and above, while Peptoid 1-C134mer showed initial significance at 0.78 μM to 1.56 μM, however, did not show significance until 12.5 μM and above. Peptoid 1-11mer showed a statistical increase in biofilm formation at 0.39 μM but showed a significant decrease from 3.125 μM to 12.5 μM and at 50 μM. LL-37 showed significance at 1.56 μM but not again until 12.5 μM and above. Amoxicillin showed significant difference from the no treatment control starting at a concentration of 6.35 μM, however, ciprofloxacin did not show a significant difference at any concentration. Values for both experiments were calculated as OD490 (Treated)/OD490 (Untreated) * 100. Statistics were performed using 2-way ANOVA, comparing each antimicrobial to the no treatment control. P values are: <0.0001 = ****, between 0.0001 and 0.001 = ***, between 0.001 and 0.01 = **, and between 0.01 and 0.05 = *.