# Resistance of \(L\). _monocytogenes_ and \(S\). Typhimurium
## 3 Results and Discussion
### Influence of the Biofilm Age on the Inactivation Kinetics
For this reason, significant differences between the log-reductions have been observed in Figure 3a, where one and seven day(s) old biofilms were treated for only 10 min (Section 3.2). As mentioned before, the latter phenomenon is probably the result of a limited/slower diffusion of the plasma species into the biofilm. Thirdly, if the final cell densities (\(N_{res}\)) that were obtained following 30 min of CAP treatment are compared with each other, no significant differences can be observed between both biofilm ages. In other words, the CAP inactivation efficacy decreases in terms of required treatment time, i.e., a prolonged treatment time is required as the biofilm ages due to a slower penetration of the CAP species, but the same (residual) final population can still be obtained. Due to the higher initial cell density (\(N_{0}\)) for the one-day old biofilm, however, higher log-reductions can be obtained for this biofilm age as compared to the seven days old biofilms, although only significantly for the selective medium. Finally, with respect to the percentage of sub-lethal injury as function of the treatment time, differences can again be observed between both biofilm ages. For the one-day old biofilms, the percentage of sub-lethally injured cells increases rapidly until a maximum percentage of approximately 90% is obtained following 7.5 min of CAP treatment. After this, the percentage of sub-lethal injury \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Model Parameters**} & \multicolumn{2}{c}{_L. monocytogenes_} & \multicolumn{2}{c}{**S. Typhimurium**} \\ \hline  & **One-Day Old** & **7 Days Old** & **One-Day Old** & **7 Days Old** \\ \hline \({}^{1}\) Log\({}_{10}\)\(N_{0}\) general medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm B}\) 7.145 \(\pm\) 0.071 & \({}^{\rm A}\) 6.151 \(\pm\) 0.220 & \({}^{\rm A}\) 6.431 \(\pm\) 0.068 & \({}^{\rm A}\) 5.857 \(\pm\) 0.229 \\ \({}^{1}\) Log\({}_{10}\)\(N_{0}\) selective medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm B}\) 7.154 \(\pm\) 0.071 & \({}^{\rm A}\) 6.218 \(\pm\) 0.237 & \({}^{\rm A}\) 6.140 \(\pm\) 0.089 & \({}^{\rm A}\) 5.397 \(\pm\) 0.249 \\ \hline \({}^{1}\)\(k_{max}\) general medium (1/min) & \({}^{\rm B}\) 1.265 \(\pm\) 0.142 & \({}^{\rm A}\) 0.253 \(\pm\) 0.057 & \({}^{\rm A}\) 1.308 \(\pm\) 0.154 & \({}^{\rm A}\) 2.730 \(\pm\) 0.785 \\ \({}^{1}\)\(k_{max}\) selective medium (1/min) & \({}^{\rm B}\) 1.735 \(\pm\) 0.172 & \({}^{\rm A}\) 0.278 \(\pm\) 0.078 & \({}^{\rm A}\) 1.534 \(\pm\) 0.198 & \({}^{\rm A}\) 2.598 \(\pm\) 0.687 \\ \hline \({}^{1}\) Log\({}_{10}\)\(N_{res}\) general medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm A}\) 3.504 \(\pm\) 0.133 & \({}^{\rm A}\) 2.661 \(\pm\) 1.710 & \({}^{\rm A}\) 2.972 \(\pm\) 0.125 & \({}^{\rm A}\) 3.474 \(\pm\) 0.158 \\ \({}^{1}\) Log\({}_{10}\)\(N_{\rm res}\) selective medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm A}\) 2.935 \(\pm\) 0.132 & \({}^{\rm A}\) 3.501 \(\pm\) 0.557 & \({}^{\rm A}\) 2.134 \(\pm\) 0.161 & \({}^{\rm A}\) 2.680 \(\pm\) 0.174 \\ \hline \({}^{1}\) Log-reduction general medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm A}\) 3.641 \(\pm\) 0.150 & \({}^{\rm A}\) 3.470 \(\pm\) 1.724 & \({}^{\rm B}\) 3.460 \(\pm\) 0.143 & \({}^{\rm A}\) 2.383 \(\pm\) 0.278 \\ \({}^{1}\) Log-reduction selective medium (log(CPU/cm\({}^{2}\))) & \({}^{\rm A}\) 4.219 \(\pm\) 0.149 & \({}^{\rm A}\) 2.717 \(\pm\) 0.606 & \({}^{\rm B}\) 4.006 \(\pm\) 0.184 & \({}^{\rm A}\) 2.716 \(\pm\) 0.304 \\ \hline \multicolumn{1}{c}{RMSE general medium (_/_)} & 0.4354 & 0.7330 & 0.4198 & 0.5714 \\ \multicolumn{1}{c}{RMSE selective medium (_/_)} & 0.4329 & 0.7620 & 0.5468 & 0.6263 \\ \hline \hline \end{tabular}  
* Influence biofilm age: for each microorganism and each growth medium, model parameters bearing different superscripts (no letters in common) are significantly different (\(p\leq 0.05\)). Parameters bearing the lowest values have been indicated with ’A’, while those bearing the highest values have been indicated with ’B’.  
\end{table} 
Table 1: Estimated model parameters [PERSON] et al.