## 3 Results
vulgaris_ showed the best activity against viable _Listeria_ cells on the fourth day (_p_ = 0.0003 and \(p\) = 0.0005, respectively), with a 4 log (_p_ = 0.0001) and 3 log (_p_ < 0.0001) reduction in microbial load, respectively, observed at the end of the study (Figure 1c,d). Good anti-_Listeria_ activity also emerged when the mixtures of EOs were used, confirming that the synergy between the selected associated compounds is still maintained when added to the coating (Figure 2). After only 24 h the _M. piperita_/_T. vulgaris_ mixture showed a significant difference compared to the control (_p_ = 0.009), displaying a 2 log reduction in the microbial load of the pathogen, and reaching a 4 log reduction on the fourth day (Figure 2e). This EO/EO association allows the reduction of the concentration of use of both compounds (see Table 2), combining the efficacy of _M. piperita_, in the first hours of experimentation, with the marked anti-_Listeria_ activity of _T. vulgaris_, a synergy that was detectable until the end of the experiment. An excellent efficacy was also observed using the associations _C. limon_/_T. vulgaris_ (_p_ = 0.002), followed by _C. limon_/_M. piperita_ (_p_ = 0.009), on the third day of testing (Figure 2a,c). The association _C. limon_/_S. officinalis_ and _M. piperita_/_S. officinalis_ yielded the best activity against viable _Listeria_ cells on the 4 th and 7 th day, respectively, and this good synergistic effect was maintained by the last mixture until the end of the study (_p_ = 0.0009). The association _S. officinalis_/_T. vulgaris_ showed the worst result than the other mixtures. Edible Antimicrobial Coating Added with a Mixture of EOs and bacLP17 against L. monocytogenes NCTC10888 on Artificially Contaminated Shrimp Samples  
The results showed good anti-_Listeria_ activity for the coatings added with the four EOs and bacLP17 in combination, with significant differences in _L. monocytogenes_ NCTC10888 viable counts compared to the control. The combination of the two types of natural compounds again showed good synergy inside the coatings as well, with consequent anti-_Listeria_ activity detectable at much lower values than their singular use. Figure 3 shows the mean of the _L. monocytogenes_ NCTC 10888 bacterial load (log CFU/g) found in the contaminated samples packaged either with doped (bacLP17 alone and in combination with the EOs) or undoped (control) coatings, after storage at 4 \({}^{\circ}\)C.  
When added to the coatings, bacLP17 showed an early activity against _L. monocytogenes_ NCTC10888 at 24 h, with clear efficacy maintained and improved until the end of the experiments (Figure 3a). Once again, the presence of _C. limon_ in the bacLP17/_C. limon_ mixture ensured its efficacy from the first hours of contact (24 h), as well as a significant reduction in bacterial counts on days 4 and 7 (_p_ = 0.0001 and \(p\) < 0.0001, respectively) (Figure 3b). The best result in terms of reduction of _L. monocytogenes_ bacterial load was obtained using the bacLP17/_M. piperita_ combination, with a marked reduction of viable cells already after 24h (_p_ = 0.002), and a subsequent increase until the end of the experiment (_p_ < 0.0001) (Figure 3c). Lastly, regarding the combinations between bacLP17 and two EOs, all the latter compounds exerted a synergistic effect with bacLP17 against _L. monocytogenes_ NCTC10888. Here, we report that the best result obtained was by adding to the coating the bacLP17/_M. piperita_/_T. vulgaris_ combination. As shown in Figure 3d, there was a significant antibacterial effect on viable _Listeria_, with an increasing trend from the first hours to the end of the experiment (7 days) (_p_ < 0.0001).