Browsing by Author "Santos, I."
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- 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.
- Characterization of Listeria monocytogenes isolates recovered from human clinical cases occurring in Portugal between 2008 and 2012Publication . Magalhães, Rosa; Ferreira, Vânia; Santos, I.; Almeida, Gonçalo; Teixeira, Paula
- Cheese-related listeriosis outbreak, Portugal, March 2009 to February 2012Publication . Magalhães, R.; Almeida, G.; Ferreira, V.; Santos, I.; Silva, J.; Mendes, M. M.; Pita, J.; Mariano, G.; Mâncio, I.; Sousa, M. M.; Farber, J.; Pagotto, F:; Teixeira, P.In Portugal, listeriosis has been notifiable since April 2014, but there is no active surveillance programme for the disease. A retrospective study involving 25 national hospitals led to the detection of an outbreak that occurred between March 2009 and February 2012. The amount of time between the start of the outbreak and its detection was 16 months. Of the 30 cases of listeriosis reported, 27 were in the Lisbon and Vale do Tejo region. Two cases were maternal/neonatal infections and one resulted in fetal loss. The mean age of the non-maternal/neonatal cases was 59 years (standard deviation: 17); 13 cases were more than 65 years-old. The case fatality rate was 36.7%. All cases were caused by molecular serogroup IVb isolates indistinguishable by pulsed-field gel electrophoresis and ribotype profiles. Collaborative investigations with the national health and food safety authorities identified cheese as the probable source of infection, traced to a processing plant. The magnitude of this outbreak, the first reported food-borne listeriosis outbreak in Portugal, highlights the importance of having an effective listeriosis surveillance system in place for early detection and resolution of outbreaks, as well as the need for a process for the prompt submission of Listeria monocytogenes isolates for routine laboratory typing.
- Distribution and characterization of Listeria monocytogenes clinical isolates in Portugal, 1994–2007Publication . Almeida, G.; Morvan, A.; Magalhães, R.; Santos, I.; Hogg, T.; Leclercq, A.; Teixeira, P.In recent years, the number of cases of listeriosis has increased worldwide. Ninety-five isolates of Listeria monocytogenes recovered from Portuguese human cases of listeriosis have been characterized by biotyping (cadmium and arsenic sensitivity), polymerase chain reaction (PCR) grouping, and by pulsed-field gel electrophoresis (PFGE) applying the enzymes AscI and ApaI. Isolates were classified into one of three PCR groups; IVb (71.6%), IIb (17.9%), and IIa (10.5%). Four biotypes were differentiated: sensitive to arsenic/cadmium (48.4%), arsenic-sensitive and cadmium-resistant (25.3%), resistant to arsenic and sensitive to cadmium (18.9%), and resistant to both heavy metals (7.4%). Combined analyses of AscI and ApaI patterns yielded a total of 58 PFGE types with five sets (G, Jb, KKa, Me, and U) of Portuguese strains, each of which were indistinguishable by PFGE typing. In the present study, it was demonstrated that there are recurrent pulsotypes and that some were the same pulsotypes linked to outbreaks in France. In addition, there are some pulsotypes spread throughout the country, while others only appear in a restricted region. This study allowed the assembly of a first large pulsotype database of Portuguese clinical strains.
- 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
- Foci of contamination of Listeria monocytogenes in different cheese processing plantsPublication . Almeida, G.; Magalhães, R.; Carneiro, L.; Santos, I.; Silva, J.; Ferreira, V.; Hogg, T.; Teixeira, P.Listeria monocytogenes is a ubiquitous bacterium widely distributed in the environment that can cause a severe disease in humans when contaminated foods are ingested. Cheese has been implicated in sporadic cases and in outbreaks of listeriosis worldwide. Environmental contamination, in several occasions by persistent strains, has been considered an important source of finished product contamination. The objectives of this research were to (i) evaluate the presence of L monocytogenes within the factory environments and cheeses of three processing plants, artisanal producer of raw ewe's milk cheeses (APC), small-scale industrial cheese producer (SSI) and industrial cheese producer (ICP) each producing a distinct style of cheese, all with history of contamination by L monocytogenes (ii) and identify possible sources of contamination using different typing methods (arsenic and cadmium susceptibility, geno-serotyping, PFGE). The presence of markers specific for 3 epidemic clones (ECI-ECIII) of L monocytogenes was also investigated: Samples were collected from raw milk (n = 179), whey (n = 3), cheese brining solution (n = 7), cheese brine sludge (n = 505), finished product (n = 3016), and environment (n = 2560) during, at least, a four-year period. Listeria monocytogenes was detected in environmental, raw milk and cheese samples, respectively, at 15.4%, 1.1% and 13.6% in APC; at 8.9%, 2.9% and 3.4% in SSI; and at 0%, 21.1% and 0.2% in ICP. Typing of isolates revealed that raw ewe's milk and the dairy plant environment are important sources of contamination, and that some strains persisted for at least four years in the environment. Although cheeses produced in the three plants investigated were never associated with any case or outbreak of listeriosis, some L monocytogenes belonging to specific PFGE types that caused disease (including putative epidemic clone strains isolated from final products) were found in this study.
- Genetic diversity of L. monocytogenes isolated from Portuguese cheesesPublication . Almeida, G.; Magalhães, R.; Santos, I.; Joana, B.; Hogg, T.; 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.
- ListeriosePublication . Almeida, Gonçalo; Magalhães, Rosa; Santos, I.; Ferreira, V.; Silva, Joana; Mendes, M.M.; Nabais, P.; Fernandes, M.G. Mariana; Mâncio, M.I.; Sousa, M.M.; Teixeira, Paula
- Listeriosis: is it a problem?Publication . Silva, J.; Teixeira, P.; Barbosa, J.; Almeida, G.; Santos, I.; Magalhães, R.