## 3 Results and Discussion
### Biofilm Eradication
What is more, in some cases, results were higher for samples pretreated by QE. The action of QE and QAC is generally based on the interactions with cell membranes, disruption of membrane integrity, and leakage of intracellular content, including ATP [28,30]. Due to the fact that the bioluminescence measurement is based on the ATP determination, the higher results of RLU/cm\({}^{2}\) may be caused by higher levels of ATP releasing from cells after treatment by QAC at higher concentrations. The results obtained using the conventional plate count method and luminometry were positively correlated (\(r\) = 0.84), but this relationship was not very strong. This fact may be due to the differences between the two detection methods. The plate count procedure evaluates the number of living bacterial cells able to grow on agar media, while luminometry detects the ATP levels. Of course, there is no perfect test method to detect biofilms on tested surfaces. Therefore, we used these two different methods to estimate biological material on the test surfaces [8]. Figure 2: Effect of mature biofilm eradication by disinfectants: (**A**) \(N\)-ethyl-\(N\),\(N\)-dimethylhexadecylammonium bromide (QAC) and (**B**) peracetic acid (PAA) acting alone or in combination with _Q. saponaria_ extracts (QE). Plate count method (CFU/cm\({}^{2}\)). Values with the different superscript lowercase signs are statistically different (\(p\) < 0.05). Lowercase letters for PAA results compared to those for QAC: \({}^{\mathrm{a}}\)\(p\) > 0.05; \({}^{\mathrm{b}}\) 0.001 \(<p\) < 0.05; \({}^{\mathrm{c}}\)\(p\) < 0.001. Lowercase numbers for disinfectants compared to those for QE+ disinfect: \({}^{\mathrm{1}}\)\(p\) > 0.05; \({}^{\mathrm{2}}\) 0.001 \(<p\) < 0.05; \({}^{\mathrm{3}}\)\(p\) < 0.001. Figure 4 shows exemplary images of _Asaia_ spp. biofilm before (Figure 4A) and after treatment with QE and PAA (Figure 4B). Microscopic observations confirmed a significant reduction in the number of adhered _Asaia_ cells. Regular cell adhesion to the glass surface was observed before treatment. After QE and PAA action, bacterial cells covered only around 10-20% of the total surface area. The synergistic action of antimicrobials against bacterial biofilms is well known. Changes in strain resistance and possible antibiotic synergy in combination with significant killing effects have also been noted by [PERSON] et al. for _Staphylococcus epidermidis_ and by [PERSON] et al. for _Pseudomonas aeruginosa_ biofilms [36,37]. Other agents that stimulate the action of antibiotics or disinfectants include enzymes, sodium salts, metal nanoparticles, acids, chitosan derivatives, and plant extracts. These combinations increase antimicrobial activity and reduce the concentration of biocides required. The in vitro antibacterial and antibiofilm activity of various plant extracts in synergy with erythromycinocyanin against erythromycin-resistant group A streptococci was also evaluated [38]. These various antimicrobial substances influence biofilm structure via various mechanisms and with different efficiencies [11]. Figure 3: Effect of mature biofilm eradication by disinfectants: (**A**) \(N\)-ethyl-\(N\),\(N\)-dimethylhexadecylammonium bromide (QAC) and (**B**) peracetic acid (PAA) acting alone or in a combined action with _Q. saponaria_ extracts (QE). Luminometric method (RLU/cm\({}^{2}\)). Values with the different superscript lowercase signs are statistically different (_p_ < 0.05). Lowercase letters for PAA results compared to those for QAC: \({}^{\text{a}}\)\(p\)\(>\) 0.05; \({}^{\text{b}}\) 0.001 \(<\) \(p\)\(<\) 0.05; \({}^{\text{c}}\)\(p\)\(<\) 0.001. Lowercase numbers for disinfectants compared to those for QE+ disinfectant: \({}^{\text{1}}\)\(p\)\(>\) 0.05; \({}^{\text{2}}\) 0.001 \(<\) \(p\)\(<\) 0.05; \({}^{\text{3}}\)\(p\)\(<\) 0.001. Saponins from _Q. saponaria_ also belong to this group, as active compounds facilitating the action of disinfectants commonly used in the food industry.