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- Study of Biological Hazards Present on the Surfaces of Selected Fruits and VegetablesPublication . Noronha, Lúcia; Castro, Ana; Ferreira, Vânia; Magalhães, Rui; Almeida, Gonçalo; Mena, Cristina; Silva, Joana; Teixeira, PaulaThis study evaluated the microbial load on the surface of fruits with rough and very pronounced textured peels, namely pineapples and melons (cantaloupe), and investigated the presence of foodborne pathogens in these products since they are usually eaten raw. Similarly, lettuce is one of the most common salad vegetables consumed raw in Portugal, it therefore being important to study the microbial status of lettuce leaves. Enumerations of aerobic mesophilic counts, Enterobacteriaceae, Escherichia coli and coagulase-positive staphylococci, as well as detection of Listeria monocytogenes and Salmonella spp., were performed for all samples. Only in melon samples were E. coli and coagulase-positive staphylococci not detected. Contamination with L. monocytogenes varied from 2.5% and 15% in pineapple/melon and lettuce samples, respectively. Salmonella spp. were not detected. All coagulase-positive staphylococci had similar characteristics and none exhibited multidrug resistance. L. monocytogenes isolates belonged to serogroups II (1/2c or 3c), or to serogroup IV (4b, 4d and 4e). None were found to be resistant to antibiotics commonly used in therapy of listeriosis.
- Campylobacter spp. as a foodborne pathogen: a reviewPublication . Silva, Joana; Leite, Daniela; Fernandes, Mariana; Mena, Cristina; Gibbs, Paul Anthony; Teixeira, PaulaCampylobacter is well recognized as the leading cause of bacterial foodborne diarrheal disease worldwide. Symptoms can range from mild to serious infections of the children and the elderly and permanent neurological symptoms. The organism is a cytochrome oxidase positive, microaerophilic, curved Gram-negative rod exhibiting corkscrew motility and is carried in the intestine of many wild and domestic animals, particularly avian species including poultry. Intestinal colonization results in healthy animals as carriers. In contrast with the most recent published reviews that cover specific aspects of Campylobacter/campylobacteriosis, this broad review aims at elucidating and discussing the (i) genus Campylobacter, growth and survival characteristics; (ii) detection, isolation and confirmation of Campylobacter; (iii) campylobacteriosis and presence of virulence factors; and (iv) colonization of poultry and control strategies.
- Study of cytolethal distending toxin (cdt ) in campylobacter coli using a multiplex polymerase chain reaction assay and its distribution among clinical and food strainsPublication . Fernandes, Mariana; Mena, Cristina; Silva, Joana; Teixeira, PaulaFrom a collection of 242 food isolates of Campylobacter spp. 72 were identified as Campylobacter jejuni and 170 as Campylobacter coli and of 112 isolates from clinical sources, 92 were identified as C. jejuni and 20 as C. coli. The results for food isolates were in contrast to other reported identifications. Twenty C. coli strains from clinical cases of Campylobacter that occurred in Portugal and 170 isolated from poultry products were examined for the presence of cytolethal distending toxin (cdt) by multiplex polymerase chain reaction assay. CdtA, cdtB, and cdtC were present in 100% of the clinical strains. With respect to the food isolates, the cdtA and cdtC genes were detected in 99.4% of the strains and cdtB in 98.8%. Small point mutations or major deletions within the primer binding sites are possible explanations for these observations but need to be further investigated.
- Occurence of Listeria monocytogenes in food products collected in Portugal from retail establishments and food plantsPublication . Mena, C.; Carneiro, L.; Silva, I.; Magalhães, R.; Almeida, G.; Teixeira, P.
- Segurança microbiológica e química de compostos orgânicosPublication . Mena, Cristina; Vasconcelos, Marta; Silva, Fátima; Teixeira, Paula
- Traditional methods for isolation of Listeria monocytogenesPublication . Magalhães, Rui; Mena, Cristina; Ferreira, Vânia; Almeida, Gonçalo; Silva, Joana; Teixeira, PaulaConventional methods for the detection of Listeria monocytogenes in foods and environmental samples relies on selective pre-enrichment, enrichment, and plating. This is followed by confirmation of suspected colonies by testing a limited number of biochemical markers.
- Bacteria: Listeria monocytogenesPublication . Magalhães, R.; Mena, Cristina; Ferreira, Vânia; Silva, Joana; Almeida, Gonçalo; Gibbs, Paul; Teixeira, Paula
- Segurança microbiológica e química de compostos orgânicosPublication . Mena, Cristina; Vasconcelos, Marta; Silva, Fátima; Teixeira, Paula
- Occurence of Listeria monocytogenes in food products collected in Portugal from retail establishments and food plantsPublication . Mena, C.; Carneiro, L.; Santos, I.; Magalhães, R.; Almeida, G.; Teixeira, P.