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- First confirmed human outbreak of Listeria monocytogenes in PortugalPublication . Almeida, G.; Magalhães, R.; Santos, I.; Ferreira, V.; Silva, J.; Mendes, M. M.; Nabais, P.; Fernandes, M. G. Mariano; Mâncio, M. I.; Sousa, M. M.; Teixeira, Paula
- Biofilm formation by persistent and non-persistent listeria monocytogenes strains on abiotic surfacesPublication . Magalhães, R.; Ferreira, V.; Biscottini, G.; Brandão, T. R. S.; Almeida, G.; Teixeira, PaulaContaminated food with Listeria monocytogenes is the predominant route of transmission of listeriosis to humans, a severe illness with a high mortality rate. Food processing environments can be colonized by persistent strains, repeatedly isolated for months or years. This study aimed to investigate the biofilm formation capacity of six strains of L. monocytogenes that persisted for long periods in two cheese processing plants in comparison to seven strains isolated sporadically from the same plants. Persistent strains produced more biofilm than non-persistent strains on stainless steel and silicon rubber surfaces; no significant differences were observed on polyvinyl chloride (PVC). In a polystyrene microtiter plate assay with crystal violet staining, no evidence was found that persistent strains have higher ability to form biofilm than non-persistent strains, and no correlation was identified between biofilm formation in the microtiter plate and on the three other surfaces tested.
- Clinical isolates of L. monocytogenes: serotyping, biotyping and susceptibility to antibioticsPublication . Almeida, G.; Ferreira, V.; Magalhães, R.; Barbosa, J.; Silva, J.; Teixeira, P.; Hogg, T.
- Epidemiological data on listeriosis in Portugal: 2003 – 2008Publication . Almeida, G.; Magalhães, R.; Hogg, T.; Teixeira, P.
- Behavior of Listeria monocytogenes isolates through gastro-intestinal tract passage simulation, before and after two sub-lethal stressesPublication . Barbosa, J.; Borges, S.; Magalhães, R.; Ferreira, V.; Santos, I.; Silva, J.; Almeida, G.; Gibbs, P.; Teixeira, P.The effects of previous exposure to sub-lethal acidic and osmotic stresses on the survival of Listeria monocytogenes during exposure to gastro-intestinal (GI) tract simulation, was investigated. Six L. monocytogenes strains isolated from cheeses were selected and exposed to high salt concentrations or acidic conditions and their viability compared in quick and slow digestions. The results demonstrated that (i) all isolates were more sensitive to the exposure to acidic than to osmotic sub-lethal conditions (ii) significant differences (p < 0.05) between the two types of digestion were observed; in slow digestion, the log reduction was higher for all the tested isolates (iii) all isolates were inhibited in the presence of bile salts for both types of digestion (iv) differences between quick and slow digestion were not observed (p > 0.05) after exposure to either osmotic or acidic stress (v) a higher cellular inactivation (p < 0.001) was observed during the passage through the GI tract simulation after exposure to osmotic than to acidic stresses and (vi) neither osmotic nor acidic sub-lethal stresses conferred resistance to simulated GI tract conditions.
- Persistence of L. monocytogenes in artisanal cheese producing plantsPublication . Almeida, G.; Santos, I.; Magalhães, R.; Joana, B.; Hogg, T.; Teixeira, P.
- Listeriosis: is it a problem?Publication . Silva, J.; Teixeira, P.; Barbosa, J.; Almeida, G.; Santos, I.; Magalhães, R.
- Enterobacter sakazakii and other pathogens in powdered infant formula (PIF)Publication . Magalhães, R.; Almeida, G.; Teixeira, P.
- Characterization of Listeria monocytogenes isolated from human cases of listeriosis occurred in Portugal in 2008Publication . Magalhães, R.; Almeida, G.; Teixeira, P.
- Listeria: is it a problem?Publication . Barbosa, J.; Ferreira, V.; Albano, H.; Magalhães, R.; Santos, I.; Castro, A.; Silva, J.; Almeida, G.; Teixeira, P.