## 2 Materials and Methods
### Recovery and Counting of Surviving C. albicans SC5314 on PE Stripes  
Subsequently to a single or combined PTW and PPA treatment, the surviving colony forming units (CFUs) were recovered. Based on Equation (1), the CFU mL\({}^{-1}\) was calculated [42; 43]:  
\[\frac{CFU}{ml}=\frac{10^{x}}{v}\cdot\frac{\sum c_{y}+\sum c_{y+1}}{n_{y}+0,1n_{ y+1}} \tag{1}\]  
\(10^{x}=\) the dilution factor for the lowest dilution  
\(v=\) the volume of diluted cell suspension per plate in mL  
\(\sum c_{y}=\) the total number of colonies on all (\(n_{y}\)) plates of the lowest evaluated dilution level \(10^{-x}\)  
\(\sum c_{y+1}=\) the total number of colonies on all (\(n_{y+1}\)) plates of the next highest dilution level evaluated \(0^{-(x+1)}\).  
After the calculation of Equation (1) for the CFU mL\({}^{-1}\), the reduction factor (RF) was determined as follows via Equation (2):  
\[\text{RF}=\text{MV}_{\text{c}}\text{log}_{10}-\text{MV}_{\text{s}}\text{log}_{10} \tag{2}\]  
\(\text{MV}_{\text{c}}\text{log}_{10}=\) mean value of the CFU mL\({}^{-1}\) of the references (control)  
\(\text{MV}_{\text{s}}\text{log}_{10}=\) mean value of the CFU mL\({}^{-1}\) of the treated specimens  
For the detection of CFU mL\({}^{-1}\), the treated PE strips were transferred into 10 mL nutrient broth as described above and shaken for 15 min at 300 rpm. The resulting _C. albicans_ suspensions were used to prepare the dilution series. Using the surface-spread-plate count method, the CFUs were countable after incubation at 37 \({}^{\circ}\)C for 12-18 h. The volume of 100 \(\mu\)L of all serial dilutions was plated out. Serial dilutions were performed as 1 to 10 dilutions. The detection limit was 10 CFU mL\({}^{-1}\). CFUs were counted manually.  
Calculations of the Reduction Factor (\(\widetilde{RF}\) ) of the Single and Combined PTW/PPA Treatment  
The combination of the PTW- and PPA-treatment may result in different effects. They can be additive, synergistic or simply reveal a decreased antimicrobial efficacy (antagonistic).  
The experiments were evaluated by determining the non-logarithmic reduction factor (RF). This was calculated as the ratio between the concentration of yeast cells in the reference and the concentration of yeast cells in a treated sample (Equation (3)):  
\[RF=\frac{n_{\text{MO}}^{Ref}}{n_{\text{MO}}^{Sam}} \tag{3}\]  
\[n_{\text{MO}}^{Ref}\ :\text{ \it concentration of microorganism\ of the reference}\]  
\[n_{\text{MO}}^{Sam}\ :\text{ \it concentration of microorganism\ of the treated sample}\]  
\[\widetilde{RF}=\text{log}_{10}(RF) \tag{4}\]  
The standard deviation of the reduction factor (ARF) was calculated via Equations (5)-(8):  
\[\Delta RF=\sqrt{\left(\frac{\partial RF}{\partial n_{\text{MO}}^{Ref}}\cdot \Delta n_{\text{MO}}^{Ref}\right)^{2}+\left(\frac{\partial RF}{\partial n_{ \text{MO}}^{Sam}}\cdot\Delta n_{\text{MO}}^{Sam}(i)\right)^{2}} \tag{5}\]  
\[\frac{\partial R}{\partial n_{\text{MO}}^{Ref}}=\frac{1}{n_{\text{MO}}^{Sam} (i)} \tag{6}\]  
\[\frac{\partial R}{\partial n_{\text{MO}}^{Sam}}=-\frac{n_{\text{MO}}^{Ref}}{ \partial n_{\text{MO}}^{Sam}(i)^{2}} \tag{7}\]\[\Delta RF=\sqrt{\left(\frac{1}{n_{MO}^{Sam}(i)}\cdot\Delta n_{MO}^{Ref}\right)^{2}+ \left(\frac{n_{MO}^{Ref}}{n_{MO}^{Sam}(i)^{2}}\cdot\Delta n_{MO}^{Sam}(i)\right)^ {2}} \tag{8}\]  
\[\Delta n_{MO}^{Ref}:error\;of\;reference\]  
\[\Delta n_{MO}^{Sam}(i):error\;of\;sample\;i\]  
\[\Delta RF:error\;of\;reduction\;factor\]