Salmonella enterica Optimizes Metabolism After Addition of Acyl-Homoserine Lactone Under Anaerobic Conditions.

Acyl-homoserine lactones (AHLs) are quorum sensing (QS) signaling molecules that mediate cell-to-cell communication in Gram-negative bacteria. Salmonella does not produce AHL, however, it can recognize AHLs produced by other species through SdiA protein modulating important cellular functions. In this work, the influence of the N-dodecanoyl-DL-homoserine lactone (C12-HSL) on glucose consumption, metabolic profile, and gene expression of Salmonella throughout the cultivation time in Tryptic Soy Broth (TSB) under anaerobic conditions was evaluated. Analysis of the supernatant culture in high-performance liquid chromatography (HPLC) revealed lower glucose uptake after 4 and 6 h of the addition of C12-HSL. Gas chromatography-mass spectrometry (GC-MS) based analysis of the intracellular metabolites revealed C12-HSL perturbation in the abundance levels of metabolites related to the metabolic pathways of glycerolipids, purines, amino acids, and aminoacyl-tRNA biosynthesis. The real-time quantitative PCR (RT-qPCR) indicated that Salmonella increase expression of genes associated with nucleoside degradation and quantification of metabolites supported the induction of pentose phosphate pathway to ensure growth under lower glucose consumption. The obtained data suggest an important role of C12-HSL in the optimization of metabolism at a situation of high population densities.

Pseudomonas spp. and Serratia liquefaciens as Predominant Spoilers in Cold Raw Milk.

The storage of fresh raw milk at low temperature does not prevent proliferation of psychrotrophic bacteria that can produce heat-resistant proteolytic enzymes contributing to the reduced shelf life of dairy products. This study aimed to identify the dominant psychrotrophic proteolytic enzyme-producing population of raw milk from Brazil. Raw milk samples collected in 3 different cooling tanks in Brazil were stored at optimal (45 h at 4 °C followed by 3 h at 7 °C) and suboptimal (45 h at 7 °C followed by 3 h at 10 °C) conditions to simulate farm storage and transportation allowed by Brazilian laws. The highly proteolytic enzyme-producing strains isolated from stored cold raw milk were characterized by repetitive sequence-based Polymerase Chain Reaction (PCR) analysis. This clustering resulted in 8 different clusters and 4 solitary fingerprints. The most proteolytic isolates from each rep-cluster were selected for identification using miniaturized kit, 16S rDNA and rpoB gene sequencing. Serratia liquefaciens (73.9%) and Pseudomonas spp. (26.1%) were identified as the dominant psychrotrophic microorganisms with high spoilage potential. The knowledge of milk spoilage microbiota will contribute to improved quality of milk and dairy products.

Selenium bioaccumulation in shiitake mushrooms: a nutritional alternative source of this element.

UNLABELLED: Mushrooms have effective mechanisms to absorb and accumulate trace elements from substrates and, therefore could be used as a strategy to produce mineral-enriched food and nutritional supplements. This study aimed to enrich shiitake mushrooms with selenium (Se), an important dietary element in human health. Strains of Lentinula edodes (Berk.) were grown on artificial logs composed of eucalyptus sawdust, and were subjected to cold shock in water containing sodium selenite (Na(2)SeO(3) ) at concentrations of up to 1.28 mM. The content of Se in the mushrooms increased linearly with increasing amounts of Na(2)SeO(3) added to the cold water although above 0.96 mM, mushroom formation was inhibited. Concentrations greater than 17 mg Se 100/g of dried mushrooms were observed after treatment with 0.64 mM Na(2)SeO(3). Shiitake mushroom had a demonstrate potential to offer an effective and economical way to produce Se-enriched products and, the strategy of adding selenite in cold water, used in this study, showed promising once it does not interfere with mycelial growth. PRACTICAL APPLICATION: Selenium is an essential trace element for both human and animals and is required for the 21st amino acid, selenocysteine, which is used for the synthesis of about a dozen selenoenzymes. In this study, it is demonstrated that shiitake mushroom is a good Se accumulator and only one step during fructification was necessary to obtained enriched mushroom. Se enriched shiitake mushroom can be considered to be an excellent source of this element and used to consumption in different ways.

Occurrence of Listeria monocytogenes in salami

Eighty-one samples of four different types of salami (Friolan, Hamburguese, Italian and Milanese), belonging to five brands, and purchased at Rio de Janeiro market, were evaluated for the occurrence of "Listeria monocytogenes, The pathogen was detected in 13.3(per cent) of Italian type samples of salami, while "L. innocua" occurred in 6.5(per cent) of the Italian type and 16.6(per cent) of the Milanese type. The remaining samples were negative for "Listeria" spp

Isolamento de Salmonella sp e Staphylococcus aureus no processo do abate suíno como subsídio ao sistema de Análise de Perigos e Pontos Críticos de Controle - APPCC / Isolation of Salmonella sp and Staphylococcus aureus at swine slaughtering as subsidy for HACCP, the Hazard Analysis and Critical Control Point system

O presente estudo foi realizado para avaliar a presença de Salmonella sp e o número de Staphylococcus aureus na superfície de carcaças suínas e caracterizar os perigos microbiológicos em diferentes etapas do abate e pontos críticos de controle (PCCs), através da quantificação de riscos (odds ratio). Um total de 120 esfregaços superficiais de carcaça suína foi coletado em um matadouro-frigorífico, após o escaldamento/depilação (ponto A), antes da evisceração (B), após evisceração e serragem da carcaça (C) e após 24 horas de refrigeração (D). Salmonella sp foi encontrada com uma freqüência média de 11,7 por cento (14) nas carcaças, enquanto o número de S. aureus variou entre 1,2 e 1,5 log UFC/cm² em 11,7 por cento das carcaças amostradas, sem evidenciar diferença estatística entre os pontos A, B, C e D. Pode-se concluir que os riscos de contaminação por Salmonella sp e S. aureus foram os mesmos nas etapas do abate de suínos consideradas neste estudo.

Enumeração de bactérias em leite cru, utilizando a técnica de contagem direta por microscopia de epifluorescent (Direct Epifluorescent Filter Technique - DEFT) / Enumeration of bacteria in raw milk, utilizing the straight technique of tally by microscopy of epifluorescência (Direct Epifluorescent Filter Technique - DEFT)

Avaliou-se o método rápido de análise quantitativa de bactérias por microscopia de epifluorescência (DEFT) no leite cru tipo C recebido pelo Laticínios Escola da Universidade Federal de Viçosa, Viçosa-MG. Um total de 190 amostras foram quantificadas pelo método DEFT e pelo método oficial de contagem padrão de mesófilos aeróbios em placa (CPP). Pôde-se observar a distinguir células coradas de alaranjado (consideradas viáveis) e células coradas de verde ( consideradas mortas), sendo que apenas as alaranjadas foram enumeradas. O resultado da análise de regressão línea apresentou um coeficiente de correção r = 0,83, sendo que a equação de regressão ficou Y = 0,68X + 1,96; onde Y = log10 UFC/mL (CPP). O limite de detecção apresentado pelo método DEFT ficou em 5,3 x 10³ CME/mL. O método DEFT apresentou um CV de 1,6 por cento. Baseando-se nas análises comparativas, pode-se inferir que o método DEFT tem um grande potencial para ser usado no Brasil para avaliar o nível de contaminação do leite cru tipo C. Além da possibilidade da sua aplicação em outros estudos na área de alimentos.