Abstract Escherichia coli is one of the most important bacteria associated with the consumption of meat products causing human disease, with bovines as the main reservoir for this organism. Escherichia coli serogroups producing the Shiga toxin (referred as STEC) include both O157:H7 and non-O157 strains can cause Hemolytic Uremic Syndrome (HUS). STEC have been previously founded in raw meat sampled at slaughterhouses. The goals of this study were 1) to detect STEC O157 and non-O157 strains in meat cuts and products (beef and pork) in TIF and non-TIF slaughterhouses, as well as butcheries, in southern Sonora, Mexico, and 2) to verify the antibiotic resistance/susceptibility pattern of E. coli strains, which contain any toxin- producing gene. To achieve the first aim, two selective media (TS-SMAC agar and Rainbow® agar O157) were employed to obtain putative O157:H7 colonies, followed by multiplex PCR for the stx1, stx2, eaeA, and rfB genes, using the O157:H7 serotype as a control. No STEC O157 was found in the beef products, but some non-O157 isolates were found. These isolates contained the stx2 pathogenicity gene (1.40 %, 3/224) and/or the fliCH4 flagellar antigen (1.78 %, 4/224). This work also confirmed the susceptibility/resistance of strains with the stx2 and/or fliCH4 genes to several antibiotics and multi- resistance of all or some of these strains to trimethoprim/sulfamethoxazole, tetracycline, clarithromycin, penicillin G, oxacillin, ampicillin, and cefazolin.

Aminas biogênicas em alta concentração podem afetar a qualidade dos alimentos e causar várias doenças, pois estão presentes em produtos como frutos do mar, vinhos e outros produtos fermentados. Subprodutos do camarão são uma fonte rica de proteína hidrolisada que podem ser usadas como suplemento alimentar. Amostras (de subprodutos de camarão) de proteína seca em pó, proteínas hidrolisadas líquidas e farinha da cabeça de camarão foram analisadas para avaliar o conteúdo de histamina e tiramina. As aminas foram extraídas com ácido tricloroacético 5% e posteriormente derivatizadas com o-ftaldialdeído. A separação cromatográfica foi realizada em uma coluna analítica, Chrom SEP C18 SS 5 mm (4,6 mm × 150 mm) com eluição por gradiente, os comprimentos de onda foram λex = 335 nm e λem = 440 nm. A fase móvel utilizada foi uma mistura de tetrahidrofurano, metanol e tampão fosfato a uma vazão de 0,6 mL min-1. Sob essas condições, a repetibilidade (desvio padrão relativo < 6,55%), reprodutibilidade (< 5,60%) e exatidão foram satisfatórias. Os valores de recuperação foram 84,51, 90,75, 95,37, 98,68 e 84,29% para L-tirosina, L-triptofano, L-lisina, tiramina e histamina, respectivamente. Este método tem sido aplicado com sucesso para a quantificação de aminoácidos precursores e aminas biogênicas em matrizes diversas.

Biogenic amines in high concentration can affect the quality of foods and cause several diseases since they are present in products like seafood, wines, and other fermented products. Shrimp by-products are a rich source of protein hydrolysate that can be used as dietary supplements. Samples (from shrimp by-products) of dry protein powder, liquid protein hydrolysate and flour of shrimp head were analyzed to evaluate the histamine and tyramine contents. Amines were extracted with trichloroacetic acid 5% and derivatized with o-phthaldialdehyde. The chromatographic separation was performed in an analytical column, Chrom SEP SS C18 5 µm (4.6 mm × 150 mm) and a fluorescence detector was used with wavelengths at λex = 335 nm and λem = 440 nm. The mobile phase was a mixture of tetrahydrofuran, methanol and phosphate buffer at a flow rate of 0.6 mL min-1 using elution gradient. Under these conditions, the repeatability (relative standard deviation, RSD < 6.55%), reproducibility (< 5.60%) and accuracy were of satisfying quality. The recovery values were 84.51, 90.75, 95.37, 98.68 and 84.29% for L-tyrosine, L-tryptophan, L-lysine, tyramine and histamine, respectively. This method has been successfully applied for the quantification of precursor amino acids and biogenic amines in different matrices.

El sulforafano es un isotiocianato con propiedades antimicrobianas y anticarcinogénicas, se encuentra en una amplia variedad de vegetales del género Brassica oleracea, considerándose las más importantes el brócoli y repollo. El objetivo de esta investigación fue cuantificar sulforafano en las partes comestibles de brócoli y en hojas de repollo por cromatografía líquida de alta resolución (HPLC). La preparación de la muestra para la cuantificación del sulforafano incluye la conversión de glucorafanina a sulforafano (45 ± 2°C durante 2,5 h), extracción con diclorometano, purificación del extracto en columnas de extracción de fase sólida, y detección por HPLC-UV. En brócoli la concentración de sulforafano está en el rango de 214 µg/g bs (tallos) a 499 µg/g bs (inflorescencias). El repollo morado (101,99 µg/g bs) presentó valores mayores de sulforafano que el repollo verde (7,58 µg/g bs). Las inflorescencias de brócoli y las hojas de repollo morado son ricos en sulforafano.

Sulforaphane is an isothiocyanate which has antimicrobial and anticarcinogenic properties, this compound is found in a wide variety of plants from genus Brassica oleracea, being the most important broccoli and cabbage. The objective of this research was to quantify sulforaphane in the edible parts of broccoli and cabbage leaves by high-performance liquid chromatography (HPLC). Sample preparation for the quantification of sulforaphane include the conversion of glucoraphanin to sulforaphane (45 ± 2 °C for 2.5 h), extracted with dichloromethane, purification of the extract in columns of solid phase extraction and detection by HPLC- UV. Sulforaphane concentration in broccoli is in the range of 214 µg/g DW (stems) to 499 µg/g DW (inflorescences). The purple cabbage (101.99 µg/g DW) has values greater than the green cabbage (7.58 µg/g DW). The inflorescences of broccoli and red cabbage leaves are rich in sulforaphane.