Screening of glutamate decarboxylase activity and bile salt resistance of human asymptomic carriage, clinical, food, and environmental isolates of Listeria monocytogenes
Résumé
Following consumption, stomach acidity is the first major barrier encountered by the
food-borne pathogen Listeria monocytogenes. Analysis of low pH sensitivity and glutamate
decarboxylase (GAD) acid resistance system of 14 isolates of L. monocytogenes carried
asymptomatically by humans showed that levels of GAD activity was subjected to strain
variation. Similar variations were observed for strains responsible of 18 listeriosis, whereas in
comparison, 13 strains isolated from food and from food-processing plant environment
showed lower GAD activity. Following survival of the stomach barrier, L. monocytogenes
also has to resist to bile salts encountered in the small intestine. Analysis revealed that all
strains tested were able to grow in presence of bile salts with concentrations as high as those
encountered in the small intestine and had the previously identified Bile Salt Hydrolase
(BSH) activity. Strain variation was observed but there was no relationship between the origin
of the strains and the ability to degrade bile salts.
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Licence : CC BY NC ND - Paternité - Pas d'utilisation commerciale - Pas de modification