Anti-listerial inhibitory lactic acid bacteria isolated from commercial cold smoked salmon

The natural microflora of cold-smoked fish at the end of shelf-life are lactic acid bacteria (LAB). Some of these display a capacity to inhibit spoilage as well as several strains of pathogenic micro-organisms, e.g. Listeria monocytogenes which is isolated frequently from cold-smoked salmon (CSS). Eight batches of sliced vacuum-packed CSS from Norway, Scotland and Spain were collected at retail. Packs were stored at 5 1C and examined for chemical and microbiological characteristics, at purchase date and at expiration date. pH, water activity and salt content were similar to available data on lightly preserved fish products. There was a consistent pattern in the development of the microflora on CSS; the initial level of LAB was low on freshly produced CSS (102 cfu g 1); however, storage in vacuum packaging at refrigeration temperature was elective for LAB. At the end of the stated shelf-life these micro-organisms, represented mainly by Lactobacillus spp., attained ca.107 cfu g 1 while Enterobacteriaceae counts were consistently lower (105 cfu g 1), which indicates the ability of LAB to grow and compete with few carbohydrates available and in the presence of moderate salt concentrations. L. monocytogenes was not found in any sample. Forty-one percent of LAB strains isolated exhibited inhibitory capacity against Listeria innocua, in a plate assay. A majority of the inhibitory effects were non-bacteriocinogenic, but nevertheless were very competitive cultures which may provide an additional hurdle for improved preservation by natural means. r 2005 Elsevier Ltd. All rights reserved

Modified Pseudomonas agar: new differential medium for the detection/enumeration of Pseudomonas aeruginosa in mineral water

Pseudomonas aeruginosa has been implicated as a foodborne and waterborne pathogen and is now considered a primary infectious agent. In the present study, the survival of P. aeruginosa inoculated in mineral water was evaluated by drop counts on Pseudomonas Agar Base (PAB), PAB with CN supplement X107, PAB with cetrimide, PAB with nalidixic acid, and these media with added FeSO4. Initial counts, before starvation, were the same in all media tested. Following this period, P. aeruginosa became sensitive to PAB with added cetrimide. The addition of FeSO4 did not improve the recovery of stressed P. aeruginosa but gave colonies a typical dark brown colour being easily differentiated from other species that can grow at 42 C. The modified Pseudomonas agar medium was also tested with several P. aeruginosa strains, other species of Pseudomonas, and other genera. Only P. aeruginosa strains (pyocyanin positive) produced the typical colonies. Our results demonstrate that Pseudomonas agar with ferrous sulphate, used for the differentiation of P. aeruginosa colonies, and nalidixic acid, used as an inhibitor of Gram-positive bacteria, might be a useful medium for the detection of injured P. aeruginosa in mineral water

Improved methods for the enumeration of heterotrophic bacteria in bottled mineral waters

At this time the European Union regulations require that the heterotrophic plate counts (HPC) of mineral waters be assessed at two recovery temperatures: 22°C for 72 h and 37°C for 24 h. This procedure is time consuming and expensive. Development of new rapid methods for microbiological assessment of the microbial flora in the bottled water is an industry-driven need. The objectives of this work were to develop a method for the HPC that utilises only one recovery temperature and one incubation period and evaluate the use of, the LIVE/DEAD® BacLight™ Bacterial Viability Kit, 5-cyano-2,3-ditotyl tetrazolium chloride (CTC) and impedance methods to enumerate viable bacteria in bottled mineral water. Results showed that incubation at 30°C could be used instead of incubation at 22°C and 37°C. Good correlation exists between counts at 30°C and counts at 22°C (r>0.90) and all the pathogens important in mineral water analyses grow similarly at 30°C and 37°C during 24 h. It was demonstrated that impedance methods might be useful to the mineral water industry as a rapid indicator of microbiological quality of the water. Results obtained with BacLight and CTC were similar to those obtained with plate counts

Bacteriófagos no tratamento de feridas

As infecções bacterianas, particularmente as causadas por bactérias resistentes aos antibióticos, permanecem a principal causa de morte entre pacientes hospitalizados com queimaduras e feridas. Para além da terapêutica sistémica, um elemento-chave na gestão de feridas infectadas é a aplicação local de antimicrobianos eficazes. Os bacteriófagos (ou fagos) têm demonstrado um elevado potencial de cura no tratamento de feridas infectadas com estirpes bacterianas resistentes aos antibióticos.Bacterial infections, particularly the ones caused by antibiotic resistant bacteria, remain as the main cause of death among hospitalized patients with burns and ulcers. Besides systemic therapy, a key element on wound management is the local application of effective antimicrobial agents. Bacteriophages (or phages) have been shown as promising candidates (used alone or as complementary to antibiotic therapy) to target antibiotic-resistant bacteria on wound treatment

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

Induction of stress tolerance in Lactobacillus delbrueckii ssp. bulgaricus by the addition of sucrose to the growth medium

The lactic acid bacteria (LAS) play an important role in the production of fermented foods. The development of concentrated cultures of LAS, for inoculating the production vat directly (bulk starters), has eliminated many problems traditionally involved in their preparation and maintenance by the food industry. For industrial use, LAS are often preserved in a frozen or dried form, the latter preparations having lower transport and storage costs (Kets et aI. 1996). Dried cultures, however, lose viability/activity during storage, especially when kept at room temperature (Champagne et aI. 1991; Teixeira et aI. 1995a, b; Castro et aI. 1996). Attempts to improve the survival of LAS during drying have already been tried (Linders et aI. 1997b; Gardiner et aI. 2000). Previous results indicated a direct relationship between the presence of compatible solutes in LAS and their ability to survive drying conditions. Such solutes include amino acids, amino acid derivatives, quaternary amines, sugars and tetrahydropyrimidines (Kets & De Sont, 1994; Kets et aI. 1994, 1996). It has been reported for severa I strains of lactobacilli that these organisms are probably unable to accumulate compatible solutes during the very short period of the drying process, and therefore they should be accumulated prior to the drying process (Kets & De Sont, 1994; Leslie et aI. 1995; Kets et aI. 1996; Linders et aI. 1997b). The aim of the present work was to investigate the effect of adding sucrose to the growth medium of Lactobacil/us delbrueckii ssp. bulgaricus on its survival during heating, spray drying and during the time of storage.info:eu-repo/semantics/publishedVersio

Insensitivity of alkenone carbon isotopes to atmospheric CO₂ at low to moderate CO₂ levels

Atmospheric pCO2 is a critical component of the global carbon system and is considered to be the major control of Earth’s past, present and future climate. Accurate and precise reconstructions of its concentration through geological time are, therefore, crucial to our understanding of the Earth system. Ice core records document pCO2 for the past 800 kyrs, but at no point during this interval were CO2 levels higher than today. Interpretation of older pCO2 has been hampered by discrepancies during some time intervals between two of the main ocean-based proxy methods used to reconstruct pCO2: the carbon isotope fractionation that occurs during photosynthesis as recorded by haptophyte biomarkers (alkenones) and the boron isotope composition (δ11B) of foraminifer shells. Here we present alkenone and δ11B-based pCO2 reconstructions generated from the same samples from the Plio-Pleistocene at ODP Site 999 across a glacial-interglacial cycle. We find a muted response to pCO2 in the alkenone record compared to contemporaneous ice core and δ11B records, suggesting caution in the interpretation of alkenone-based records at low pCO2 levels. This is possibly caused by the physiology of CO2 uptake in the haptophytes. Our new understanding resolves some of the inconsistencies between the proxies and highlights that caution may be required when interpreting alkenone-based reconstructions of pCO2

Characterization of bacPPK34 a bacteriocin produced by Pediococcus pentosaceus strain K34 isolated from “Alheira”

Different lactic acid bacteria were isolated during different stages in the production of “Alheiras”, a traditionally fermented sausage produced in the north of Portugal, between 2005 and 2007, in a total of 484 isolates. One of 484 isolates (K34) produced a bacteriocin, designated as bacPPK34, and was identified as a strain of Pediococcus pentosaceus by 16S rRNA sequencing. The highest bacteriocin production was noted at late log/early stationary phase after 15e18 h of growth in MRS broth at 37 ºC (3200 AU/ml) against Enterococcus faecalis ATCC 29212 and 12800 AU/ml against Listeria monocytogenes (L1, L2, L3). bacPPK34 was between 2.5 kDa and 6.2 kDa in size, as determined by tricine-SDS-PAGE. Complete inactivation or significant reduction in antimicrobial activity was observed after treatment of cell-free supernatants with proteinase K, pepsin and trypsin. No change in activity was recorded when treated with catalase. The bacteriocin was resistant to treatments with lipase and detergents Triton X-100, Tween 20, SDS, NaCl, urea and EDTA. Furthermore, the bacteriocin remained active after 2 h at pH 2e12 and temperature treatments at 60, 80, 100 ºC, 1 month of storage at º20 and 4 ºC and 20 min at 121 ºC. Addition of bacPPK34 to a mid-log culture of L. monocytogenes and E. faecalis ATCC 29212 inhibited growth. The bacteriocin did not adhere to the surface of the producer cells.info:eu-repo/semantics/acceptedVersio

Incidence of Listeria monocytogenes in different food products commercialized in Portugal

Several types of food products on sale in Portugal, were examined for the presence of Listeria monocytogenes. Secondary enrichments, in Fraser broth, were analysed by the mini-Vidas LMO, enzyme-linked fluorescent immunoassay technique. Positive samples were confirmed by isolation on Oxford and PALCAM selective agars followed by biochemical characterization. Of 1035 samples, 72 (7.0%) were positive for L. monocytogenes, the majority being from raw products (milk, meat, fish, flour) although some heat-processed or fermented foods (ready-to-eat) were also positive. In Portugal, a predilection for fresh cheese was indicated as a potential risk for consumers

Do echinoderm genomes measure up?

Echinoderm genome sequences are a corpus of useful information about a clade of animals that serve as research models in fields ranging from marine ecology to cell and developmental biology. Genomic information from echinoids has contributed to insights into the gene interactions that drive the developmental process at the molecular level. Such insights often rely heavily on genomic information and the kinds of questions that can be asked thus depend on the quality of the sequence information. Here we describe the history of echinoderm genomic sequence assembly and present details about the quality of the data obtained. All of the sequence information discussed here is posted on the echinoderm information web system, Echinobase.org