## 4 Conclusions  
Multiple _L. monocytogenes_ strains can be present in the same food matrix as a result of cross-contamination with different serotypes of the pathogen. In this context, taking also into account the probability of occurrence in foods as discussed in the Introduction, four _L. monocytogenes_ strains were selected among a collection of isolates recovered from naturally contaminated minced pork meat samples. Strain selection took place, primarily, on the basis of the microorganism's serotypes recovered from the minced meat samples, and the selected strains represented the most commonly detected serotypes of the pathogen in foods. The resulting mixture of strains used to inoculate the meat product, further used in our study, simulated the worst real-case contamination scenario and achieved a wide degree of biodiversity during the postprocessing contamination of an RTE meat product with _L. monocytogenes_. At this point, we feel it should be acknowledged that the higher and lower initial concentrations of serotypes 4b and 1/2c, respectively, in the mixture of strains, might also result in noticeable changes to the growth potential for each pathogen's  
Figure 2: Dominance rates for _L. monocytogenes_ serotypes 1/2a (\(\blacksquare\)), 1/2b (\(\blacktriangle\)), 1/2c (\(\blacklozenge\)), and 4b (\(\bullet\)) during storage of an RTE cooked, cured meat product inoculated with a cocktail of _L. monocytogenes_ strains. (**a**) Storage of the meat product at 4 °C; (**b**) storage of meat product at 10 °C. Symbols represent the dominance rates for the respective _L. monocytogenes_ serotype on each sampling day, calculated through Equation (1) (see the text). Serotyped _L. monocytogenes_ strains on each sampling day originate as the result of pathogen isolation from the three replicates performed and the subsequent differentiation by mPCR; the error bars represent the standard deviation of these three replicates. serotype [17; 46]. However, given the fact that the meat product is able to support the growth of _L. monocytogenes_, we could say that the observed disproportion of the serotype distribution at the beginning of storage not only hindered, but, characteristically, marked the existence of population dynamics during the strain competition of the pathogen, as revealed by the final distribution and prevalence (%) at the end of the meat product's storage period (Table 1). In conclusion, although the present findings are considered to be more preliminary in nature and the results of this study are limited by the scope of investigation due to the lack of a vigorous statistical analysis using multiple biological replicates from more than one independent trial, they indicate, however, a strain-specific competitive advantage in the growth of _L. monocytogenes_. Foods contaminated with _L. monocytogenes_ strains of multiple serotypes present differences in the dominance dynamics of the pathogen's serotypes, due to strain competition during storage at different temperatures, which can lead to the suppression or predominance of certain serotypes. Intraspecies interactions are thus inferred. In this way, the observed underrepresentation of serotype 4b in favor of serogroup 1/2 strains (ser. 1/2a, 1/2b, and 1/2c) among the _L. monocytogenes_ strains isolated from food, particularly those recovered during detection and/or enumeration of the pathogen in meat and the products thereof, may be partially explained. Further studies are needed to elucidate the mechanisms that exist at the molecular level, through gene expression, which will simulate the transition of the pathogen from food to human host and will contribute towards our greater understanding regarding the observed underrepresentation of _L. monocytogenes_ among the food isolates. These studies may shed light on how certain serotypes of the pathogen become capable of adapting and outcompeting or surviving better than others in the food matrix.