Beatriz Martínez

Prevalence and antimicrobial resistance patterns of Salmonella from different raw foods in Mexico.

The presence of Salmonella was determined in 116 samples of poultry meat, 81 samples of pork, 73 samples of beef, 33 samples of cheese, 61 samples of fish, and 78 samples of vegetables collected from retail stores and supermarkets in Hidalgo State (Mexico). Ninety-three Salmonella strains isolated from raw foods were characterized, and MICs were determined for 10 antimicrobials. Salmonella was detected in 35.3% of poultry meat, 30.3% of cheese, 21.8% of vegetable, 17.3% of pork, and 15.1% of beef samples, but no Salmonella was detected in fish samples. Significantly higher counts were obtained in chicken meat (P = 0.0001), pork (P = 0.0116), cheese (P = 0.0228), and vegetables (P = 0.0072) obtained from retail stores compared with those samples obtained from supermarkets. Salmonella isolates had high levels of resistance to ampicillin (66.7% of isolates), tetracycline (61.3%), and chloramphenicol (64.5%) and low levels of resistance to cefotaxime (0%), gentamicin (3.2%), and kanamycin (4.3%). Higher levels of quinolone resistance were found in isolates from poultry meat and vegetables compared with that in other foods tested. High levels of multiresistant strains were found in all foods tested except fish, ranging from 100% of pork samples to 47.1% of vegetable samples. The present study revealed that Salmonella prevalence was higher in foods from retail stores than in foods from supermarkets. Resistance rates observed for Salmonella were largely comparable to those reported in other countries for most antimicrobials, although resistance to chloramphenicol tended to be higher.

Differentiation of farmed and wild turbot ("Psetta maxima"): proximate chemical composition, fatty acid profile, trace minerals and antimicrobial resistance of contaminant bacteria

The proximate, cholesterol, fatty acid and trace mineral compositions in the flesh of farmed and wild turbot (Psetta maxima) were evaluated. Additionally, the potential influence of the use of antimicrobial agents in the bacteria carried by farmed turbot was investigated. For this purpose, a total of 144 Pseudomonas spp. and 127 Aeromonas spp. were isolated and tested for their susceptibility to 12 antimicrobials by a disk diffusion method. Farmed turbot contained higher fat, cholesterol and calories as well as lower moisture content than its wild counterpart. The fatty acid profile of farmed turbot included higher levels of myristic, pentadecanoic, palmitoleic, gadoleic, cetoleic, linoleic, linolenic, stearidonic, eicosadienoic and eicosapentaenoic acids, and lower levels of stearic, arachidonic, docosapentaenoic and docosahexaenoic acids than its wild counterpart. The proportions of polyunsaturated fatty acids and n-3/n-6 ratios were higher in wild turbot than in farmed turbot. With respect to trace minerals, no toxic levels were found, and higher amounts of Cd, Co, Cu, Fe, Mn, Pb and Zn, as well as lower amounts of Cr, were found in farmed turbot relative to wild turbot. The antimicrobial resistance of Pseudomonas spp. and Aeromonas spp. were quite similar, with only the trimethoprim-sulfamethoxazole resistance of Aeromonas spp. isolated from farmed turbot being higher than those isolated from wild turbot. In the case of ampicillin, Pseudomonas spp. isolated from wild turbot showed higher resistance levels than those of their counterparts isolated from farmed turbot. In conclusion, the nutritional parameters of wild turbot are more adequate with respect to nutritional recommendations, while no differences were observed in food safety derived from trace mineral concentrations or the antimicrobial resistance of bacteria isolated from wild and farmed turbot.

Evaluation of different strategies to mask boar taint in cooked sausage

The use of smoking and/or spices was evaluated for their ability to mask boar taint in frankfurters manufactured from entire pigs with high levels of androstenone. Five frankfurter types were considered: control, smoked, flavouring+smoked, spicy and spicy+smoked. A trained panel in androstenone perception carried out a sensory profile on the different sausages. The highest scores for androstenone perception (odour, flavour and aftertaste) were found in frankfurters that included no masking strategy which indicated the effectiveness of the evaluated strategies. Regarding masking strategies, the contribution of spices and smoking to sensory perception of frankfurters was detected by the panellists. Smoking was the best strategy to mask androstenone odour, while the use of spices masked androstenone odour to a greater extent than androstenone flavour. Only the combined use of spices and smoking was able to eliminate the perception of androstenone. The application of this strategy in frankfurters could be an alternative in the commercialization of entire pigs.

Sistema de aglutinación con látex para el diagnóstico rápido de la leptospirosis en Cuba

OBJETIVOS: Evaluar la sensibilidad, la especificidad, la reproducibilidad y la estabilidad de cinco sistemas de aglutinacion con latex disenados para detectar anticuerpos contra leptospira en sueros de humanos y de animales, basados en los serogrupos de Leptospirade mayor circulacion en Cuba. METODOS: Se realizo un estudio analitico descriptivo con 706 sueros humanos (65 sueros positivos a anticuerpos contra leptospira mediante microaglutinacion (MAT) y hemaglutinacion (HA); 156 sueros negativos, segun MAT y HA; 485 sueros de 424 pacientes con signos clinicos o epidemiologicos de leptospirosis); y 29 sueros de animales (16 equinos, 6 bovinos, 5 porcinos, 1 canino y 1 ovino). Todas las muestras se evaluaron con cinco conjugados de latex con celulas enteras de Leptospira interrogans de los cuatro serogrupos de mayor circulacion en Cuba en el periodo entre 2002 y 2004. Con las celulas obtenidas de los cultivos celulares de cepas tipo se obtuvieron cuatro conjugados especificos (latex-Canicola, latex-Icterohaemorrhagiae, latex-Pomona y latex-Sejroe) y un conjugado de latex con la mezcla de las celulas de esos cuatro serogrupos a partes iguales (latex-Pool). Adicionalmente, las muestras se evaluaron con el sistema comercial de aglutinacion con latex Lepto Tek Dri Dot (bioMerieux, Francia). La estabilidad y la reproducibilidad de los conjugados de latex se evaluaron mediante controles mensuales durante 6 meses con sueros positivos y negativos. RESULTADOS: De los sistemas evaluados, la mejor combinacion de sensibilidad y especificidad se observo con el conjugado latex-Pool (93,8% y 90,4%, respectivamente). La mejor combinacion de valores predictivos positivos y negativos se observo con el conjugado latex-Sejroe (90,9% y 95,8%, respectivamente), seguido del conjugado latex-Pool (94,2% y 96,6%, respectivamente). Los valores predictivos positivo y negativo del sistema comercial Lepto Tek Dri Dot fueron 78,5% y 88,4%, respectivamente. De las 137 muestras de pacientes positivas a alguno de los serogrupos estudiados segun MAT, los conjugados de latex lograron identificar correctamente 107 (78,1%), mientras que el conjugado latex-Pool detecto como positivos 116 sueros (84,7%). Al evaluar los sueros de animales, el conjugado latex-Pool detecto como positivos el mayor numero de sueros y tuvo la mayor coincidencia con MAT (93,1%). Se observo una adecuada estabilidad y reproducibilidad de los conjugados estudiados. CONCLUSIONES: Los conjugados de latex con celulas enteras de leptospira de los serogrupos de mayor circulacion en Cuba demostraron un grado de coincidencia con MAT similar o superior al observado con el sistema comercial Lepto Tek Dri Dot, tanto en sueros de humanos como de animales. Se recomienda extender el uso del conjugado latex-Pool en Cuba para el tamizaje inicial de anticuerpos contra leptospira.

Development of a simple method for the quantitative determination of fatty acids in milk with special emphasis on long-chain fatty acids

A new and simple method was developed for the extraction and derivatization of fatty acid (FA) in milk. Lipid extraction of milk was carried out in H2SO4/methanol. Methylation was performed for 2 h at 60°C, and FA methyl esters were recovered for chromatographic analysis by the addition of hexane. The method parameters were optimized and the simple method was compared to the official reference procedure for the extraction and methylation of FAs in milk samples. For most of the 24 FAs determined, similar or significantly higher recoveries were obtained by the simple method than by the conventional method. The simple method allows processing a high number of samples, at the same time, minimizing the sample manipulation and, consequently, the sample loss and contamination. In conclusion, the proposed method is simple, rapid, low cost, and achieves good results.

A procedure for sensory detection of androstenone in meat and meat products from entire male pigs: Development of a panel training

This study represents a proposal for training sensory panels in androstenone (AND) perception in meat and meat products. The procedure consists of four main parts: (1) selection and training of a sensory panel (11 panelists) using standards with Vaseline oil media as carriers of AND and skatole (SKA); (2) developing a training method AND detection in meat; (3) dry cured meat product and (4) cooked meat product. All candidates were able to distinguish between AND, SKA and AND+SKA in Vaseline oil, order AND solutions with different concentrations and classify them in the three categories: low, medium and high. The panel was able to differentiate the meat in the three categories, but only the high level in meat products. Due to the individual features in AND perception, specific training for each type of product is required.

Sensory characteristics of meat and meat products from entire male pigs

The surgical castration of male piglets has traditionally been practised to prevent the development of boar taint in pork meat, but European rules aim to end this practice on a voluntary basis. This study represents a sensory characterization of the meat and meat products from entire male pigs. Three levels of androstenone concentration in fat were compared: low, 0-0.3mgkg-1; medium, 0.4-0.9μgkg-1 and high, 1-2.75μgkg-1. The use of meat from entire males in meat products lowered the perception of boar taint compared with fresh meat but was insufficient to totally mask it. Androstenone levels seem to influence the intramuscular fat content and hence, on texture. The perception of boar taint in meat products depends on androstenone concentration as well as on the characteristics of the product. It is necessary to develop additional strategies to totally mask androstenone perception in meat and meat products.