Leonor Silveira

Dr. Leonor Silveira

orcid

Research Focus & Metrics

Academic Career Length

16Years (2011-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2018 in International Journal of Antimicrobial Agents
Verified
Journal Article
Closed access
Joana CamposJoana Campos
Joana Campos
Joana MourãoJoana Mourão
Joana Mourão
LSLeonor Silveira
Leonor Silveira
MSMargarida Saraiva
Margarida Saraiva
CCCristina Belo Correia
Cristina Belo Correia
PAPatrícia Antunes
Patrícia Antunes

19 March 2012 in BMC Medical Genetics
Verified
Journal Article
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SSSusana Santos
Susana Santos
VMVanda Marques
Vanda Marques
MPMarina Pires
Marina Pires
LSLeonor Silveira
Leonor Silveira
HOHelena Oliveira
Helena Oliveira
Alexandra FernandesAlexandra Fernandes
Alexandra Fernandes
Background: Hypertrophic Cardiomyopathy (HCM) is a complex myocardial disorder with a recognized genetic heterogeneity. The elevated number of genes and mutations involved in HCM limits a gene-based diagnosis that should be considered of most importance for basic research and clinical medicine.Methodology: In this report, we evaluated High Resolution Melting (HRM) robustness, regarding HCM genetic testing, by means of analyzing 28 HCM-associated genes, including the most frequent 4 HCM-associated sarcomere genes, as well as 24 genes with lower reported HCM-phenotype association. We analyzed 80 Portuguese individuals with clinical phenotype of HCM allowing simultaneously a better characterization of this disease in the Portuguese population.Results: HRM technology allowed us to identify 60 mutated alleles in 72 HCM patients: 49 missense mutations, 3 nonsense mutations, one 1-bp deletion, one 5-bp deletion, one in frame 3-bp deletion, one insertion/deletion, 3 splice mutations, one 5'UTR mutation inMYH7,MYBPC3,TNNT2,TNNI3,CSRP3,MYH6andMYL2genes. Significantly 22 are novel gene mutations.Conclusions: HRM was proven to be a technique with high sensitivity and a low false positive ratio allowing a rapid, innovative and low cost genotyping of HCM. In a short return, HRM as a gene scanning technique could be a cost-effective gene-based diagnosis for an accurate HCM genetic diagnosis and hopefully providing new insights into genotype/phenotype correlations.

10 March 2023 in Antibiotics
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Journal Article
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SPSara Perestrelo
Sara Perestrelo
AAAna Amaro
Ana Amaro
MBMichael S. M. Brouwer
Michael S. M. Brouwer
MCMaria de Lurdes Tavares Clemente
Maria de Lurdes Tavares Clemente
ADAna Sofia Ribeiro Duarte
Ana Sofia Ribeiro Duarte
JAJulio Alvarez
Julio Alvarez
Antimicrobial resistance (AMR) is one of the top public health threats nowadays. Among the most important AMR pathogens, Escherichia coli resistant to extended spectrum cephalosporins (ESC-EC) is a perfect example of the One Health problem due to its global distribution in animal, human, and environmental sources and its resistant phenotype, derived from the carriage of plasmid-borne extended-spectrum and AmpC β-lactamases, which limits the choice of effective antimicrobial therapies. The epidemiology of ESC-EC infection is complex as a result of the multiple possible sources involved in its transmission, and its study would require databases ideally comprising information from animal (livestock, companion, wildlife), human, and environmental sources. Here, we present the steps taken to assemble a database with phenotypic and genetic information on 10,763 ESC-EC isolates retrieved from multiple sources provided by 13 partners located in eight European countries, in the frame of the DiSCoVeR Joint Research project funded by the One Health European Joint Programme (OH-EJP), along with its strengths and limitations. This database represents a first step to help in the assessment of different geographical and temporal trends and transmission dynamics in animals and humans. The work performed highlights aspects that should be considered in future international efforts, such as the one presented here.

RBRita Batista
Rita Batista
MSMargarida Saraiva
Margarida Saraiva
TLTeresa Teixeira Lopes
Teresa Teixeira Lopes
LSLeonor Silveira
Leonor Silveira
CCCoelho Coelho
Coelho Coelho
APAngela Pista
Angela Pista
Birds are potential carriers of pathogens affecting humans and agriculture. Aiming to evaluate the occurrence of the top three most important foodborne pathogens in free-living birds in Portugal, we investigated 108 individual fecal samples from free-living birds and one pooled sample of gull feces (n = 50) for the presence of Escherichia coli (pathogenic and non-pathogenic), Salmonella spp. and Campylobacter spp. Virulence- and antimicrobial resistance- (AMR) associated genes were detected by PCR and Whole-Genome Sequencing (WGS), and phenotypic (serotyping and AMR profiles) characterization was performed. Overall, 8.9% of samples tested positive for pathogenic E. coli, 2.8% for Salmonella spp., and 9.9% for Campylobacter spp. AMR was performed on all pathogenic isolates and in a fraction of non-pathogenic E. coli, being detected in 25.9% of them. Ten of the tested E. coli isolates were multidrug-resistant (MDR), and seven of them were Extended-spectrum β-lactamase (ESBL) producers. Among Salmonella (n = 3) and Campylobacter (n = 9), only one strain of C. jejuni was identified as MDR. Most of the identified serotypes/sequence types had already been found to be associated with human disease. These results show that free-living birds in Portugal may act as carriers of foodborne pathogens linked to human disease, some of them resistant to critically important antimicrobials.

11 October 2024 in Antibiotics
Verified
Journal Article
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CGCarlota Mateus Gonçalves
Carlota Mateus Gonçalves
LSLeonor Silveira
Leonor Silveira
JRJoão Carlos Antunes Rodrigues
João Carlos Antunes Rodrigues
RFRosália Furtado
Rosália Furtado
SRSónia Ramos
Sónia Ramos
APAngela Pista
Angela Pista
Background: Foodborne diseases are a serious public health concern, and food-producing animals are a major source of contamination. Methods: The present study analysed Escherichia coli and Salmonella spp. isolated from faecal samples of 100 fattening pigs and from 52 samples of pork meat. Results: The results showed that the majority of the analysed meat samples were considered satisfactory in terms of microbiological quality (92.3% for E. coli and 94.2% for Salmonella spp.). Salmonella spp. was identified in 5.8% of the meat samples, whereas E. coli was detected in 89.5% of all samples (69.2% in meat and 100% in faecal samples). Furthermore, 1.9% of the faecal samples contained Shiga-toxin-producing E. coli and 3.9% contained enterotoxigenic E. coli. All sequenced isolates presented virulence genes for extraintestinal pathogenic E. coli. Moreover, 75.0% of E. coli isolates from meat and 71.8% from faeces samples showed antibiotic resistance, with 40.7% and 51.4%, respectively, being multidrug-resistant (MDR). The most prevalent resistances were to tetracycline, ampicillin, and sulfamethoxazole, and one E. coli isolate showed resistance to extended-spectrum β-lactamase. Conclusions: This study highlights the role of pigs as a potential source of human contamination and the importance of a One Health approach to ensure food safety and to promote public health.

16 December 2019 in International Journal of Genomics
Verified
Journal Article
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LSLeonor Silveira
Leonor Silveira
MPMiguel Pinto
Miguel Pinto
JIJoana Isidro
Joana Isidro
APAngela Pista
Angela Pista
PTPatrícia Themudo
Patrícia Themudo
João Paulo GomesJoão Paulo Gomes
João Paulo Gomes
Gastrointestinal infections caused by nontyphoidal Salmonella (NTS) remain one of the main causes of foodborne illness worldwide. Within the multiple existing Salmonella enterica serovars, the serovar Rissen is rarely reported, particularly as a cause of human salmonellosis. Between 2015 and 2017, the Portuguese National Reference Laboratory of Gastrointestinal Infections observed an increase in the number of clinical cases caused by multidrug-resistant (MDR) S. enterica serovar Rissen, particularly from the Azores archipelago. In the present study, we analyzed by whole genome sequencing (WGS) all clinical, animal, food, and environmental isolates received up to 2017 in the Portuguese Reference Laboratories. As such, through a wgMLST-based gene-by-gene analysis, we aimed to identify potential epidemiological clusters linking clinical and samples from multiple sources, while gaining insight into the genetic diversity of S. enterica serovar Rissen. We also investigated the genetic basis driving the observed multidrug resistance. By integrating 60 novel genomes with all publicly available serovar Rissen genomes, we observed a low degree of genetic diversity within this serovar. Nevertheless, the majority of Portuguese isolates showed high degree of genetic relatedness and a potential link to pork production. An in-depth analysis of these isolates revealed the existence of two major clusters from the Azores archipelago composed of MDR isolates, most of which were resistant to at least five antimicrobials. Considering the well-known spread of MDR between gastrointestinal bacteria, the identification of MDR circulating clones should constitute an alert to public health authorities. Finally, this study constitutes the starting point for the implementation of the “One Health” approach for Salmonella surveillance in Portugal.