Evaluation of antibacterial activity against Salmonella Enteritidis

Salmonella enterica serovar Enteritidis is a well-known pathogenic bacterium responsible for human gastrointestinal enteritis mainly due to the consumption of eggs and egg-products. The first aim of this work was to study several virulence factors of a strain isolated from egg content: SEovo. First, bacterial growth was studied at several temperatures and cell morphology was observed by scanning electronic microscopy. These experiments showed Salmonella's ability to grow at low temperatures and to produce exoproducts. Next, Salmonella motility was observed performing swimming, twitching, and swarming tests. Results indicated a positive flagellar activity and the cell ability to differentiate and become hyperflagellated under specific conditions. Moreover, SEovo adherence and biofilm formation was carried out. All of these tests enabled us to conclude that SEovo is a potential pathogen, thus it can be used as a model to perform antibacterial experiments. The second part of the study was dedicated to the evaluation of the antibacterial activity of different molecules using several methods. The antibacterial effect of silver and copper aluminosilicates was tested by two different kinds of methods. On the one hand, the effect of these two antibacterial agents was determined using microbiological methods: viable cell count and agar-well diffusion. And on the other hand, the antibacterial activity was evaluated using CLSM and SYTO Red/SYTOX Green dyeing. CLSM allowed for the evaluation of the biocide on sessile cells, whereas the first methods did not. Results showed that adhered bacteria were more resistant than planktonic counterparts and that CLSM was a good alternative to evaluate antibacterial activity on fixed bacteria without having to carry out a removing step.