Refrigerated poultry breast fillets packed in modified atmosphere and irradiated: bacteriological evaluation, shelf life and sensory acceptance

In the present study the effects on shelf life and sensory acceptance of gamma-irradiated refrigerated poultry breast fillets subjected to modified atmosphere packaging (80% CO2/20% N2 or vacuum) were investigated. After irradiation with 2 kGy, sensory acceptance tests and monitoring of bacterial growth were performed in order to determine the sanitary quality of the samples. It has been found that irradiation, used in combination with modified atmosphere packaging, can double the shelf life of refrigerated poultry breast fillets by reducing the populations of aerobic mesophilic and psychrotrophic bacteria, enterobacteria, coliforms, Listeria spp. and Aeromonas spp., without significantly modifying its color or its overall appearance, the lactic acid bacteria being the most resistant to exposure to radiation and carbon dioxide.

Relación endoscópica entre duodenitis inespecífica y sobrecrecimiento bacteriano del intestino delgado / Endoscopic relationship between non specific duodenitis and snall intestine bacterial overgrowth

Cuando aparece una proliferación de la flora de tipo colónico en el intestino delgado se producen alteraciones en la digestión y absorción intestinal, que clínicamente conforman el síndrome del Sobrecrecimiento Bacteriano del Intestino Delgado (SBID). En el SBID la concentración bacteriana aumenta hasta 107-109 UFC/ml en intestino delgado. El principio del test de hidrógeno espirado es la administración de un carbohidrato (Lactulosa, dxilosa, glucosa), que al ser degradado por las bacterias produce un aumento de los niveles de hidrógeno espirado en pacientes con SBID. Hipótesis: Si la duodenitis inespecífica se manifiesta clínicamente de manera similar al (SBID) entonces puede haber una relación entre ambas patologías. Métodos: Se realizó un estudio clínico descriptivo prospectivo de una muestra seleccionada quienes tuvieron como hallazgo en la endoscopia digestiva superior duodenitis inespecífica. Se usó Video endoscopio Olympus GIF-140, en dicha endoscopia se tomó biopsia del tejido duodenal con pinza. Posteriormente el paciente fue sometido a prueba de hidrógeno en aliento aire espirado con 10 gr de Lactulosa. Resultados: La prueba de Hidrógeno en aliento resultó positiva en 18 pacientes (29,5%) y negativo en 43 (70,5%) (p=1,000). La sensibilidad fue de 29,6% y Especificidad 71% (IC 95%). Conclusiones: 1) La prueba de Hidrógeno en aire espirado con Lactulosa es una prueba con poca sensibilidad pero específica para el Diagnóstico de SBID. 2) La prevalencia de duodenitis giardiásica fue del 11,5% en la población estudiada. 3) Los hallazgos histológicos referentes a las alteraciones de las vellosidades intestinales no están correlacionados con el SBID.

When a proliferation of the flora of type colonic appears in the small intestine they are caused by alterations in the digestion and intestinal absorption, which they make up clinically the syndrome of the Small Intestine Bacterial Overgrowth (SIBO). In SIBO the bacterial concentration increased to 107-109 UFC/ml in the small intestine. The origin of the exhaled hydrogen test is the administration of a carbohydrate (Lactulose, d-xylose, glucose), which when broken down by the bacteria produce an increase in the levels of the exhaled hydrogen in patients with SIBO. Hypothesis: If the non-specific duodenitis appears clinically similar in a way to (SIBO) then there may be a connection between both pathologies. Methods: We carried out a prospective descriptive clinical trial of a selected sample who had the finding of nonspecific duodenitis in the upper endoscopy. We used Video endoscope Olympus GIF-140, in that endoscopic was taken biopsy of the duodenal tissue with forceps. Subsequently, the patient was undergone of Breath-hydrogen test with 10 gr of lactulose. Results: the hydrogen breath test was positive in 18 patients (29.5%) and negative in 43 (70.5%) (p = 1.000). The sensitivity was 29.6% and specificity 71% (95%). Conclusions: 1) Hydrogen breath test with lactulose is less sensitive but specific for the diagnosis of SIBO. 2) The prevalence of giardiasic duodenitis was 11.5% in our trial. 3.) Histological findings regarding alterations of the intestinal villi are uncorrelated with SIBO.

Biofilm formation by Listeria monocytogenes on stainless steel surface and biotransfer potential

An experimental model was proposed to study biofilm formation by Listeria monocytogenes ATCC 19117 on AISI 304 (#4) stainless steel surface and biotransfer potential during this process. In this model, biofilm formation was conducted on the surface of stainless steel coupons, set on a stainless steel base with 4 divisions, each one supporting 21 coupons. Trypic Soy Broth was used as bacterial growth substrate, with incubation at 37 ºC and stirring of 50 rpm. The number of adhered cells was determined after 3, 48, 96, 144, 192 and 240 hours of biofilm formation and biotransfer potential from 96 hours. Stainless steel coupons were submitted to Scanning Electron Microscopy (SEM) after 3, 144 and 240 hours. Based on the number of adhered cells and SEM, it was observed that L. monocytogenes adhered rapidly to the stainless steel surface, with mature biofilm being formed after 240 hours. The biotransfer potential of bacterium to substrate occurred at all the stages analyzed. The rapid capacity of adhesion to surface, combined with biotransfer potential throughout the biofilm formation stages, make L. monocytogenes a potential risk to the food industry. Both the experimental model developed and the methodology used were efficient in the study of biofilm formation by L. monocytogenes on stainless steel surface and biotransfer potential.

A phage display combined with DNA affinity magnetic system can be applied to a screening of DNA binding proteins, such as transcription factors / Un fago pantalla combinado con un sistema de afinidad magnético al ADN se puede aplicar al exámen de las proteínas de unión al ADN, tales como los factores de transcripción

Here we introduce a new approach for the screening of DNA binding proteins, using a phage library based on a phage display technique. In principal, a complementary DNA (cDNA) library based on the recombinant bacteriophage T7 expressing target proteins on its capsid (phage display) is constructed. These phage particles are hybridized with a biotinylated target DNA fragment which is immobilized on the surface of streptavidin paramagnetic particle (SA-PMP). The phage particles are released from the target DNA fragment by a nuclease treatment and the recovered phages are used to the next round of hybridization. These processes are repeated three times to amplify the target phages in the population. This simple method is faster, and more systemic than other current methods (e.g. yeast one hybrid system). As a proof of this principle, we tried to isolate transcription factors which specifically bind to the promoter region of the Arabidopsis thaliana AtGST11 gene. Two obtained candidates, RING zinc finger protein and AtHB6, showed DNA binding activity to the AtGST11 promoter region. We could validate that our new application of phage display is a superior method for isolation of DNA binding proteins with a broad range of potential applications.

Predicción del crecimiento de la Lactococcus lactis subsp. lactis en leche descramada estéril en función a la temperatura / Growth prediction of Lactococcus lactis subsp. lactis in sterile skimed milk as a function of temperature

Diversos modelos matemáticos han sido desarrollados con el objeto de predecir el comportamiento de las poblaciones bacterianas en fase de crecimiento en condiciones controladas a nivel de laboratorio, muchos de estos han sido validados en condiciones de producción, transporte y almacenamiento de alimentos. El objetivo del presente trabajo fué adaptar un modelo matemático utilizando ecuaciones obtenidas como resultado del análisis con modelos secundarios de los coeficientes de regresión de la ecuación de Gompertz, a efectos de lograr predecir las poblaciones en crecimiento de Lactococcus lactis subsp. lactis en leche en polvo reconstituida y esterilizada, controlando la temperatura en el rango desde 9 a 39°C. Con este fin, los coeficientes “A” y “B” se analizaron con el modelo de la raíz cuadrada, obteniéndose valores de R2 = 0,819 y 0,991, respectivamente, mientras que el modelo hiperbólico se utilizó para modelar los coeficientes “D” (R2= 0,812) y “M” (R2= 0,995). Finalmente se obtuvo una expresión reparametrizada del modelo original de Gompertz, sustituyendo cada coeficiente de regresión por la ecuación que lo describe, en función a las diferentes temperaturas estudiadas, siendo este modelo utilizado para predecir directamente las poblaciones del microorganismo en estudio a cualquier temperatura dentro del rango estudiado. Se obtuvieron diferencias muy pequeñas entre la población observada experimentalmente y la ajustada según la aplicación del modelo desarrollado, observándose una distribución bastante equilibrada de los valores residuales. Se recomienda utilizar este tipo de modelo para describir el crecimiento de poblaciones combinadas en productos como leche pasteurizada comercial.

Several mathematic models have been developed to predict the behavior of bacteria populations in growing phase and controlled conditions at the laboratory. Many of these models have been validated under food production, transportation and storage conditions. The objective of this study was to adapt a mathematical model using equations obtained as a result of the analysis with secondary models of regression coefficients from the Gompertz equation, to predict population of Lactococcus lactis subsp. lactis in the growing phase in reconstituted and sterilized powder milk, controlling temperature in a range of 9 to 39°C. Prediction was done by the analysis of “A” and “B” coefficients, using the square root model, obtaining R2 values = 0.819 and 0.991, respectively. Furthermore, a hyperbolic model was used for modeling “D” (R2= 0.812) and “M” (R2= 0.995) coefficients. Finally, a reparametrized expression of the original Gompertz model was obtained replacing each regression coefficient by the described equation, in relation to the different studied temperatures. Thus, this model was used to directly predict the population of microorganism under study at any temperature in the studied range. Small differences were obtained between both, the experimental and the adjusted populations, according to the application of the developed model. A well balanced distribution of the residual values was observed. The use of this type of models is recommended to describe growth of combined microorganism populations in products such as commercial pasteurized milk.