Authors
Advisor(s)
Abstract(s)
Diferentes serótipos de Listeria monocytogenes podem apresentar diferentes capacidades de reacção perante condições de stress, estando descrito que essa diferença pode estar associado à origem dos mesmos: seja essa origem alimentar ou clínica.
O vinho é uma solução complexa constituída por vários elementos com capacidade antibacteriana, estando reconhecida a sensibilidade de L. monocytogenes quando exposta à acção do vinho.
Este trabalho teve como objectivo comparar a actividade do vinho contra isolados alimentares e clínicos de L. monocytogenes, recorrendo, para tal, à elaboração das curvas de inactivação de 8 isolados clínicos e 8 isolados alimentares, após a exposição destas bactérias a vinho diluído numa proporção de 1:10 e 1:100.
Estudou-se também o efeito do vinho sobre L. monocytogenes em ambiente gastrointestinal simulado com duas matrizes alimentares diferentes: queijo fundido e uma papa de fruta para bebés.
Em vinho diluído 1:100 foram observadas diferenças significativas (p<0,05) na cinética de inactivação, e consequentemente na resistência, dos diferentes isolados de L. monocytogenes estudados. Observou-se que estas diferenças estão relacionadas com a origem dos isolados. Com efeito, os isolados de origem alimentar mostraram-se mais sensíveis à acção do vinho do que os isolados clínicos. No entanto, quando se aumentou a quantidade de vinho nos ensaios (vinho diluído 1:10) não foram encontradas diferenças significativas relacionadas com a origem dos isolados (p>0,05).
Quando foi simulado o ambiente gastrointestinal utilizando-se uma matriz de queijo fundido verificou-se que não ocorreu inactivação de nenhum dos isolados com ou sem vinho adicionado (p>0,05). No entanto, quando a matriz alimentar foi constituída por uma papa de frutas, verificou-se uma maior sensibilidade das bactérias às condições gastrointestinais, sendo de realçar o efeito adicional de inactivação quando vinho foi adicionado. De facto, a inclusão de vinho no sistema gastrointestinal simulado levou a um aumento da inactivação dos isolados testados (p<0,05) mais marcado nos isolados de origem alimentar do que nos clínicos.
Ficou assim demonstrada a grande sensibilidade de L. monocytogenes ao vinho, a qual que parece estar correlacionada com a origem dos isolados. Ficou igualmente demonstrado que a inclusão de vinho num ambiente gastrointestinal simulado pode levar a um aumento da redução de células viáveis desta bactéria. Contudo, esse efeito é dependente da matriz alimentar presente, sendo que uma matriz alimentar com forte teor lipídico e proteico oferece uma maior protecção às células de L. monocytogenes que uma matriz com forte teor de hidratos de carbono.
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.
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.