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Research Project
Clostridium difficile: prevalence in foods and study of alternative treatments to conventional therapeutics applied on C. difficile infection
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Spray drying conditions for orange juice incorporated with lactic acid bacteria
Publication . Barbosa, Joana; Brandão, Teresa R. S.; Teixeira, Paula
This work aimed to develop an orange juice powder by spray drying with lactic acid bacteria (Lactobacillus plantarum 299v and Pediococcus acidilactici HA‐6111‐2), testing their survival both during drying and storage (room temperature and 4 °C). Initially, the best conditions for spray drying were chosen to allow the best survival of each LAB: (i) inlet air temperature of 120 °C and (ii) 0.5:2 ratio of the orange juice soluble solids and drying agent added (prebiotics: 10 DE maltodextrin or gum Arabic). Survival of LAB was not affected by drying process, and it was higher when cultures were stored at 4 °C. A slightly higher protection was conferred by 10 DE maltodextrin, in the case of L. plantarum and at 4 °C. Pediococcus acidilactici was more resistant during storage at 4 °C, with logarithmic reductions lower than 1 log‐unit. It was demonstrated that it is possible to produce a functional nondairy product, orange juice powder supplemented with prebiotic compounds, containing viable LAB for at least 7 months, when stored at 4 °C.
Methods currently applied to study the prevalence of Clostridioides difficile in foods
Publication . Barbosa, Joana; Campos, Ana; Teixeira, Paula
Clostridioides difficile is responsible for most cases of antibiotic- and hospital-associated diarrhoea. Several studies have demonstrated the presence of C. difficile in different foods such as meat, raw milk, vegetables and seafood, which supports the hypothesis that foods contaminated with spores may be contributing to the exposure to and transmission of C. difficile. Generally, the prevalence of C. difficile in foods is low and there is no standard methodology for its isolation. Available methods have been optimized for stool samples rather than foods. In the majority of the studies, a similar base culture medium has been used and different selective and enrichment compounds are further added, which is, sometimes, controversial. Despite the extensive use of cycloserine and cefoxitin, as well as moxalactam and norfloxacin, many authors believe that the use of these selective supplements had an adverse effect on the recovery of C. difficile and only enabled recovery of resistant isolates from food samples. Another example is the use of sodium taurocholate to potentiate the germination of C. difficile spores; there are studies reporting that the addition of this component in the enrichment medium did not exert a beneficial effect on C. difficile recovery. Variations in sample amounts, dilution factors, incubation times, among others, may also affect the recovery of C. difficile from foods. Numerous studies have recently emerged, since there is increasing interest in C. difficile as a potentially foodborne pathogen. Thus, the purpose of this review is to summarize the methodologies currently used on the isolation/detection of C. difficile in foods and its subsequent characterization and typing.
Evaluation of a bacteriocinogenic Lactobacillus plantarum strain on the microbiological characteristics of “Alheira de Vitela”
Publication . Macieira, Ariana; Albano, Helena; Pinto, Miguel; Linheiro, Raquel; Barbosa, Joana; Teixeira, Paula
Lactic Acid Bacteria (LAB) and their bacteriocins can be successfully used as natural preservatives in meat products. This work aimed to investigate the effect of fresh and lyophilized starter cultures of an autochthonous bacteriocinogenic LAB strain (Lactobacillus plantarum ST153Ch: bac + culture) on the microbiological characteristics of “Alheira”, a traditional Portuguese smoked product. “Alheira” with the addition of fresh or lyophilized culture (ca. 108 cfu/g) and “Alheira” control (no bacteriocinogenic culture added) were produced by an industrial meat company. The antilisterial activity of this culture in this food matrix was investigated, with some samples being inoculated with Listeria monocytogenes (ca. 105 cfu/g). Detection of L. monocytogenes, Salmonella spp., sulphite reducing clostridia, Yersinia enterocolitica and enumeration of L. monocytogenes, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Enterobacteriaceae, lactic acid bacteria, yeasts and moulds were performed immediately after production and at 3, 7, 15, 21, 28, 60 and 90 days of storage at 4 ℃, according to ISO methodologies. Also, a 16S rRNA Gene Analysis was performed of the microbial communities of “Alheira” with and without the lyophilized bacteriocinogenic culture. Pathogenic and indicator organisms were not detected or were below acceptable levels in all samples. LAB counts increased during storage and reached similar values after 15 days (ca. 1010 cfu/g) in all samples. There was a clear trend for a higher reduction of L. monocytogenes in the presence of the bioprotective culture, more pronounced during the initial 15 days of storage. From the analysis of the microbial communities of samples of “Alheiras” at different stages of fermentation, Leuconostocaceae and Lactobacillaceae predominated in all the samples and Lactobacillus was the genus more prevalent in “Alheiras” after 60 days of storage with the addition of bacteriocinogenic culture.
Microbial contamination of main contact surfaces of automated teller machines from metropolitan Area of Porto
Publication . Barbosa, Joana Inês Bastos; Albano, Helena da Conceição Pereira; Silva, Fabiana Ferreira; Teixeira, Paula Cristina Maia
Automated Teller Machines (ATM) are likely to be contaminated with various microorganisms because of their contact with the hands of many users daily. The main objective of this study was to investigate ATMs as a potential source of bacterial contamination. This study was conducted in the Metropolitan Area of Porto, in which 50 swab samples were cultured on selective media. Some isolates were identified based on colonial, morphological and biochemical characteristics. Susceptibility to several antibiotics was also evaluated for each isolated organism. Most contaminated ATMs had high numbers of Enterobacteriaceae and Enterococci. Staphylococci and Enterobacteriaceae were the most prevalent bacteria found. The recovered bacterial isolates varied in their antibiotic resistance pattern; Staphylococcus spp. demonstrated the most resistant profiles. With this pioneering study in Portugal, it was demonstrated that although ATMs in metropolitan area of Porto were not highly contaminated, some potentially pathogenic bacteria were present and resistant to some commonly used antibiotics.
Microbiological characterization of different formulations of alheiras (fermented sausages)
Publication . Silva, Julieta; Barbosa, Joana; Albano, Helena; Sequeira, Maria; Pinto, Ana; Bonito, Conceição Costa; Saraiva, Margarida; Teixeira, Paula
Different ingredients in old recipes are becoming popular and the traditional alheira did not escape to this new trend. The objective of this preliminary study was to characterize microbiologically nine different formulations of alheira from five producers. In this sense, isolates obtained were characterized through different phenotypic and biochemical tests. Their susceptibility to different antimicrobials and the presence of virulence factors was also investigated. Lactic acid bacteria were the predominant microbiota, but pathogenic bacteria as coagulase-positive staphylococci, Listeria monocytogenes and Salmonella spp. as well as indicator organisms were also found. Several virulence factors were produced among the different groups of isolates, with a high incidence of isolates producing β-haemolysis. Along with their potential pathogenic activity, also several antimicrobial resistances were found being the majority of isolates classified as multi-resistant. At our knowledge, this is the first study with these new formulations of alheira. A higher number of products must be analyzed, but we believe that results obtained in this study should help to alert consumers for the need of safe cooking time/temperatures of these products.
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Fundação para a Ciência e a Tecnologia
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Funding Award Number
SFRH/BPD/113303/2015