Actividade do vinho contra Listeria monocytogenes

: comparação de isolados alimentares com clínicos

Abstract

Different serotypes of Listeria monocytogenes may have different capacities to respond under conditions of stress, being reported that this difference may be linked to its origin. Wine is a complex solution consisting of several elements which may exhibit antibacterial ability, being recognized the sensitivity of L. monocytogenes when exposed to wine. This work aimed to compare the activity of red wine against clinical and food isolates of L. monocytogenes. Inactivation curves for 8 clinical isolates and 8 food isolates were obtained exposing the bacteria to diluted red wine (1:10 and 1: 100).This work also aimed to study the effect of wine on L. monocytogenes in simulated gastrointestinal conditions with two different food matrices: a processed cheese and fruit meal for babies.Significant differences (p<0,05) were found in the kinetics of inactivation between food and clinical isolates when exposed to wine diluted 1:100.). In fact, food-borne isolates were found to be more sensitive to wine activity than the clinical isolates. However, when a lower wine dilution was used (1:10) no differences were observed related to the origin of the isolates (p>0.05).In the simulated gastrointestinal environment, only a slight inactivation level (<1 log cycle) was observed for both tested isolates (one food and one clinical) when processed cheese was used as food matrix with or without added wine. However, when the food matrix was changed to a smashed fruit meal for babies, a strong decrease in the viable cell density was achieved, being also detected an additional inactivation effect provoked by wine.. In fact, the inclusion of wine in the simulated gastrointestinal system led to an increase in the inactivation of all the isolates tested (p<0.05). This effect was more pronounced in food-borne isolate than in clinical isolate.It was demonstrated the high sensitivity of L. monocytogenes to wine, such sensitivity seems to be correlated with the origin of the isolates. It was also shown that the inclusion of wine in a simulated gastrointestinal environment leads to a higher reduction of viable cells of this bacterium. However, the extent of this effect is dependent on the food matrix present. High fat and protein content foods exert higher protection than high carbohydrate content food matrices.

Date of Award	2012
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	José António Couto (Supervisor) & Paula Teixeira (Co-Supervisor)