Partial characterization of nine bacteriocins produced by lactic acid bacteria isolated from cold-smoked salmon with activity against listeria monocytogenes

Nine LAB bacteriocin-producers, isolated from vacuum-packaged cold-smoked salmon (CSS), were phenotypically and genotypically identified as Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Enterococcus faecium, and Pediococcus acidilactici. Their bacteriocins were partially characterized. The antimicrobial spectrum was determined against Listeria monocytogenes, E. faecalis, E. faecium, and Staphylococcus aureus. The molecular size of bacteriocins ranged from 2.8 to 4.5 kDa. They were inactivated by treatment with proteolytic enzymes but not by lipolytic or glycolytic enzymes. Maximal activity against L. monocytogenes ranged between 800 and 10000 AU/mL at pH 6.5. Most of the bacteriocins maintained full activity in a pH range of 2.0 to 8.0 but were partially or completely inactivated at pH 10.0. After heating at 60°C and 100°C, only two bacteriocins from Lb. curvatus strains partially lost activity. All bacteriocins showed a narrow spectrum of activity and a high anti-listerial activity, which is characteristic of the class IIa bacteriocins. Isolated bacteriocinproducing LAB could be used successfully in the bio-preservation of CSS and development of new potential bio-preservatives for CSS active against L. monocytogenes

In vitro tests of suitability of bacteriocin-producing lactic acid bacteria, as potential biopreservation cultures in vacuum-packaged cold-smoked salmon

The objectives of this study were to ascertain the in vitro potential of nine bacteriocin-producing lactic acid bacteria (LAB) strains, isolated from vacuum-packaged cold-smoked salmon (CSS), for possible use as biopreservative cultures against Listeria monocytogenes. The antilisterial activity of cultures’ supernatants was assessed at 0.5%, 3.0% and 5.0% w/v of salt, at 5ºC, 10ºC and 25ºC both in aerobic and anaerobic atmospheres, simulating the conditions pertaining in vacuum-packaged CSS. The kinetics of growth, bacteriocin biosynthesis, the minimum inhibitory concentrations (MICs) of ten antibiotics, histamine and tyramine production of LAB strains, were determined jointly with the haemolytic activity for the enterococci. Only five strains were able to secrete active bacteriocins into the culture medium, at high salt concentrations and low temperatures, both in aerobic and anaerobic atmospheres. Enterococci showed neither haemolyt ic activity nor vancomycin resistance. The production of histamine was not observed for any of the bacteriocin-producing strains

Time to Switch to Second-line Antiretroviral Therapy in Children With Human Immunodeficiency Virus in Europe and Thailand.

Background: Data on durability of first-line antiretroviral therapy (ART) in children with human immunodeficiency virus (HIV) are limited. We assessed time to switch to second-line therapy in 16 European countries and Thailand. Methods: Children aged <18 years initiating combination ART (≥2 nucleoside reverse transcriptase inhibitors [NRTIs] plus nonnucleoside reverse transcriptase inhibitor [NNRTI] or boosted protease inhibitor [PI]) were included. Switch to second-line was defined as (i) change across drug class (PI to NNRTI or vice versa) or within PI class plus change of ≥1 NRTI; (ii) change from single to dual PI; or (iii) addition of a new drug class. Cumulative incidence of switch was calculated with death and loss to follow-up as competing risks. Results: Of 3668 children included, median age at ART initiation was 6.1 (interquartile range (IQR), 1.7-10.5) years. Initial regimens were 32% PI based, 34% nevirapine (NVP) based, and 33% efavirenz based. Median duration of follow-up was 5.4 (IQR, 2.9-8.3) years. Cumulative incidence of switch at 5 years was 21% (95% confidence interval, 20%-23%), with significant regional variations. Median time to switch was 30 (IQR, 16-58) months; two-thirds of switches were related to treatment failure. In multivariable analysis, older age, severe immunosuppression and higher viral load (VL) at ART start, and NVP-based initial regimens were associated with increased risk of switch. Conclusions: One in 5 children switched to a second-line regimen by 5 years of ART, with two-thirds failure related. Advanced HIV, older age, and NVP-based regimens were associated with increased risk of switch

Effect of storage temperature on the freshness index (K value) in cultured cachama (Colossoma sp.)

En el pescado, inmediatamente después de su muerte y durante su transporte a los puntos de comercialización, se suceden una serie de procesos autolíticos en el músculo, entre los que destacan la hidrólisis de los nucleótidos. Con el propósito de evaluar la influencia que ejerce la temperatura de almacenamiento sobre la concentración de nucleótidos para estimar la frescura del pescado, tres lotes de híbridos de cachama (Colossoma sp) se almacenaron en las siguientes condiciones: a) 0° C ± 3° C; b) 10° C ± 3° C y c) 27° C ± 3° C, por dos semanas. Las concentraciones de los nucleótidos individuales a lo largo del almacenamiento se determinaron por Cromatografía Líquida de Alta Resolución (HPLC) según el método de Iwamoto y col.[9], Los resultados indican que durante las primeras 24 horas las muestras almacenadas a 10° C presentaron la mayor tasa de hidrólisis del Adenosín Trifosfato (ATP), seguidas por las muestras almacenadas a 27° C y luego aquéllas almacenadas a 0° C. Las concentraciones de Inosina Monofosfato (IMP), Inosina (HxR) e Hipoxantina (HX) fueron independientes de la temperatura de almacenamiento. El incremento lineal en la concentración de HX observado en las tres temperaturas durante el período de almacenamiento, indica que éste puede ser usado como un buen índice de la pérdida de la frescura en estos híbridos.373 - 378BimestralAs soon as the fish dies and during its transportation to the retail centers, there are a series of autolytic processes in their tissues being the hydrolysis of the nucleotides the most important of them. These postmortem changes modify some of the original characteristics of the fish and determine its acceptance or rejection by the consumer. With the purpose of evaluating the influence that storage temperature exerts on the nucleotides concentration for estimating the freshness of fish, three lots of cachama’s hybrids (Colossoma sp) were kept under the following conditions: a) 0 °C ± 3° C; b) 10° C ± 3° C and c) 27° C ± 3° C, for two weeks at different temperatures. The concentrations of individual nucleotides through out the storage were performed using High Performance Liquid Chromatography (HPLC) by Iwamoto et al. [9] method. Results indicate that during the first 24 hours the samples stored at 10° C had the highest rate of Adenosin Monophosphate (ATP) hydrolysis followed by samples stored at 27°C and this in turn was higher than the one observed at 0° C. Inosine monophosphate (IMP), lnosine (HxR) and hipoxanthine (HX) concentrations were independent of storage temperature. The lineal increment of the HX concentration observed at all temperatures during the storage period indicates that it can be used as a good index of the loss of the freshness in these hybrids

Helicobacter pylori: Rol del agua y los alimentos en su transmisión

Helicobacter pylori&nbsp;es una bacteria Gram negativa, microaerof&iacute;lica, que coloniza eficientemente la mucosa g&aacute;strica humana. Fue aislada por primera vez en el a&ntilde;o 1982 y actualmente se considera como un importante pat&oacute;geno humano que causa diversas enfermedades gastrointestinales y adem&aacute;s se reconoce como agente carcin&oacute;geno. Se habla de una alta prevalencia en el mundo, con un mayor porcentaje en los pa&iacute;ses en v&iacute;as de desarrollo, esto probablemente relacionado con las condiciones de vida. De esta manera, el estatus socio-econ&oacute;mico es el determinante m&aacute;s importante para el desarrollo de la infecci&oacute;n por H. pylori, siendo las clases sociales m&aacute;s bajas las que exhiben mayor prevalencia. A la fecha, las rutas de transmisi&oacute;n de este microorganismo no se encuentran totalmente esclarecidas. Sobre la base de diversas evidencias epidemiol&oacute;gicas y microbiol&oacute;gicas se han propuesto varias v&iacute;as. Dentro de estas se incluye al agua y a los alimentos como posibles vectores, a pesar de la compleja detecci&oacute;n de esta bacteria en muestras distintas al tejido g&aacute;strico. H. pylori puede pasar a un estado viable no cultivable (VNC) bajo condiciones de estr&eacute;s. No obstante, se han llevado a cabo diversos estudios para evaluar la prevalencia y supervivencia de esta bacteria en diversas fuentes de agua y muestras de alimentos, cuyos resultados indican la posibilidad de que los mismos act&uacute;en como un reservorio en su transmisi&oacute;n. Por esta raz&oacute;n, el presente art&iacute;culo de revisi&oacute;n se enfoca en las evidencias que apoyan la transmisi&oacute;n de H. pylori a trav&eacute;s del agua y los alimentos.Helicobacter pylori&nbsp;is a Gram-negative, microaerophilic, which efficiently colonizes the human gastric mucosa. It was first isolated in 1982 and is now considered an important human pathogen that causes various gastrointestinal diseases and is also recognized as a carcinogen. There is a high prevalence worldwide, with a higher percentage in developing countries, probably related to living conditions. Thus, the socio-economic status is the most important determinant for the development of the infection by H. pylori, being lower social classes exhibiting the highest prevalence. To date, the routes of transmission of this organism are not fully elucidated. Based on numerous epidemiological and microbiological evidences, several transmission paths have been suggested. Among them water and food are included as potential vectors, although the detection of these bacteria is complex in distinct samples to gastric tissue. H. pylori can happen to a viable but non-culturable state (VBNC) under conditions of stress. However, there have been several studies to assess the prevalence and survival of the bacteria in various water sources and food samples. Results indicate the possibility that they act as a reservoir for transmission. For this reason, this review article focuses on the evidence supporting the transmission of H. pylori through water and food.&nbsp

Could modifications of processing parameters enhance the growth and selection of lactic acid bacteria in cold-smoked salmon to improve preservation by natural means

Several smoking conditions were examined with the objective of enhancing the numbers of lactic acid bacteria (LAB) by natural means in vacuum-packaged cold-smoked salmon during 21 days of storage at 5C. Three combinations of salting, drying, and smoking were used: (i) dry salting time of salting (2 or 6 h); (ii) wet salting (6 h) dry salting (6 h) with mor without sugar; and (iii) wet salting (6 h) dry salting (6 h) different times of smoking (2 or 6 h of drying and 2 or 6 h of smoking). Two batches were processed for each set of conditions. Determinations of pH and salt content in the water phase were carried out for products in each treatment. Microbiological analyses (total viable count, total LAB, Lactobacillus spp., and Enterobacteriaceae) also were conducted at the beginning of storage (t0) and after 21 days of refrigerated storage (t1). There were differential increases in total LAB and lactobacilli during the storage period according to the treatment performed. The most effective treatment to enhance LAB growth was 6 h of dry salting with sugar, 6 h of drying, and 2 h of smoking. These salting-drying-smoking conditions also selected the LAB as the dominant flora at the end of the storage period. The LAB promoted by these processing parameters seem to be potentially useful protective cultures because of their anti-Listeria activity. From the results of this research, we conclude that it is possible to enhance the growth of LAB in general and that of inhibitory strains in particular by suitable choices of processing parameters

Growth control of listeria innocua 2030c on vacuum-packaged cold-smoked salmon by lactic acid bacteria

Five bacteriocin-producing lactic acid bacteria (LAB): Enterococcus faecium ET05, Lactobacillus curvatus ET06, L. curvatus ET30, L. deldrueckii ET32 and Pediococcus acidilactici ET34, selected by their capacity for growth and producing inhibition in vitro at high salt-on-water content, low temperature and anaerobic atmosphere, conditions simulating cold-smoked fish,were inoculated onto salmon fillets, in co-culturewith Listeria innocua 2030c, and cold-smoked processed (dry salted for 6h; drying for 6h; smoke for 2h).The finished product was then packed under vacuum and stored at 5 °C. Enumeration of LAB and L. innocua was performed during storage. Results showed that strain E. faecium ET05 was the best biopreservative candidate for controlling L. innocua growth in vacuum-packaged cold-smoked salmon (CSS) processed under the salting/drying/smoking parameters referred above. L. curvatus ET30 and L. delbrueckii ET32 also showed a good biopreservation potential for CSS although they were less effective than the former. L. curvatus ET06 and P. acidilactici ET34 showed a bacteriostatic mode of action against the target bacteria in vitro as well as when inoculated into the salmon fillets. This study describes a potential application of five different LAB in the biopreservation of Listeria in CSS

Effects of storage temperature on the onset of rigor mortis and stability of cultured tilapia (Oreochromis spp.)

Los requerimientos de un músculo de alta calidad para la comercialización de los productos pesqueros, han estimulado la investigación sobre el efecto de la temperatura de almacenamiento en los cambios postmortem. El presente trabajo tuvo como objetivo evaluar el impacto de tres temperaturas de almacenamiento en el rigor mortis y en la estabilidad de la tilapia (O. mossambicus x O. urolepis hormorum x O. niloticus x O. aureus) durante su almacenamiento. Para la determinación del índice del rigor (IR) de las tilapias sometidas a tres temperaturas de almacenamiento se utilizó el método de desplazamiento horizontal. Las concentraciones individuales de los nucleótidos se determinaron usando cromatografía líquida de alta resolución (HPLC). Los cambios sensoriales fueron evaluados durante 21 días de almacenamiento refrigerado, mediante una escala descriptiva. También se hicieron mediciones del pH muscular y del Nitrógeno Básico Volátil Total (NVC-T). El rigor mortis ocurrió más tempranamente en el pescado almacenado a 0° C (24 h) en comparación con el pescado almacenado a 10° C (48 h) y a 27° C (no se alcanzó 100% de IR). El pH cayó más rápidamente (P<0.05) en el pescado almacenado a 10° C. Al final del almacenamiento, el NBV-T no superó los 30 mgN/100g permitidos en productos pesqueros. Para cada condición de temperatura, la tilapia parece acumular hipoxantina (Hx) junto con pequeñas cantidades de inosina (INO) paralelamente con la degradación de inosina monofosfato (IMP). La evaluación sensorial indicó una vida útil de 21 días para las tilapias almacenadas a 0° C en comparación con 9 días para las tilapias almacenadas a 10° C.339 - 345BimestralThe requirements for high flesh quality in raw fish products for commercial markets have stimulated research on the effect of storage temperature on post mortem changes in muscle tissues in fish. The objective of this study was to evaluate the impact of three storage temperatures on the onset of rigor mortis and stability of tilapia (O. mossambicus x O. urolepis hormorum x O. niloticus x O. aureus) during storage. Rigor index (RI) of tilapia subjected to three different storage temperatures was assessed using the method of horizontal displacement. The concentrations of individual nucleotides were performed using high performance liquid chromatography (HPLC). Sensory changes were evaluated through a descriptive scale over 21 days of refrigerated storage. Muscle pH and total volatile basic nitrogen (TVBN) were also measured. Onset of rigor occurred much earlier (P<0.05) pH drop occurred in fish stored at 10° C. The TVBN at the end of the storage period did not exceed the value of 30 mg N/100g allowed in fish products. The tilapia seems to accumulate hypoxanthine (Hx) together with small quantities of inosine (INO) parallelly to the degradation of the inosine monophosphate (IMP), for each condition of temperature. Descriptive sensory evaluation indicated a shelf life of 21 days for the tilapias stored at 0° C compared to 9 days for the tilapias stored at 10° C

Biogenic amines, microbiological and sensory evaluation of sardine (sardinella aurita) during ice storage

En el presente trabajo se evaluaron los cambios de los parámetros sensoriales, microbiológicos (aerobios mesófilos, psicrófilos y bacterias productoras de histamina), así como la formación de aminas biógenas, en tres lotes: I (junio), II (julio) y II (noviembre) de sardinas (Sardinella aurita) sometidas a refrigeración en hielo (4° C) en cavas isotérmicas, bajo dos condiciones: sardinas enteras (EN) y evisceradas-descabezadas (EV) por un período de almacenamiento en hielo de 20 días. Los resultados microbiológicos indicaron un bajo recuento inicial de aerobios mesófilos (103 UFC/g) en los tres lotes evaluados, los cuales aumentaron hasta alcanzar valores finales de 105 UFC/g. Los microorganismos psicrófilos comenzaron a aumentar al sexto día de almacenamiento (103 UFC/g), incrementándose notablemente hasta 107 UFC/g al final del estudio, para ambas condiciones. Los niveles de bacterias productoras de histamina, se mantuvieron bajos durante toda la experiencia (≤ 10-103 UFC/g). Los resultados de la evaluación sensorial indicaron un grado de frescura óptima desde el inicio hasta el segundo día del almacenamiento; entre los 3-13 días las sardinas conservaron buena calidad y desde los 14 días hasta el final del almacenamiento (20 d) se consideraron de baja calidad. Estas etapas fueron observadas en ambas condiciones, sin embargo para EV se observó mejor calidad. La evaluación sensorial resultó ser la más idónea para medir estabilidad y frescura de las sardinas en sus dos condiciones.494 - 502BimestralThe present study evaluated the changes of sensorial parameters, microbiological examinations (aerobic mesophiles, psychrotrophs and histamines-producers bacteria) and formation of biogenic amines in three lots: I (June), II (July) and III (November) of sardine (Sardinella aurita). Each lot was subjected to refrigeration in isothermic box with ice (4°C), under two conditions: whole (WS) and eviscerated-behaed (ES) for 20 days. The microbiological result show a low mesophilic initial count (103 UFC/g) in these lots, which increased until reaching final values of 105 UFC/g. While psychrophilic microorganisms began lo increase from sixth day of storage (103 UFC/g) and reached up lo 107 UFC/g at the end of study, for both conditions. The histamine-forming bacteria count were low, during all the experiences (≤ 10-103 UFC/g). The results of sensorial evaluation indicated a good freshness grade from the beginning until the second day of storage; between 3-13 days sardines conserved a good quality and later from 14 days until storage ended (20 d) they were considered with low quality. These stages were observed in both storage conditions, however better quality was determinate in eviscerated-behead. The sensorial evaluation was most suitable lo measure sardine freshness and stability