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At least 127 records · Page 7Linked to original sources

Effects of high-pressure processing on Listeria monocytogenes, spoilage microflora and multiple compound quality indices in chilled cold-smoked salmon.

AIMS: To evaluate the effect of high-pressure processing (HPP) on Listeria monocytogenes, microbial and chemical changes and shelf-life in chilled cold-smoked salmon (CSS). METHODS AND RESULTS: First, challenge tests with L. monocytogenes were carried out using HPP of the product at 0.1 (control), 150, 200 and 250 MPa. Secondly, storage trials with the naturally contaminated product and HPP at 0.1 (control) and 200 MPa were realized. Shelf-life, microbial changes and chemical changes were determined and existing predictive models and multiple compound quality indices evaluated. HPP with 250 MPa did not inactivate L. monocytogenes but significant lag phases of 17 and 10 days were observed at ca 5 and 10 degrees C, respectively. HPP with 200 MPa had a marked effect on both colour and texture of CSS. CONCLUSIONS: High-pressure processing was unable to prevent growth of L. monocytogenes or spoilage of chilled CSS. Existing mathematical models allowed growth rates of L. monocytogenes and shelf-life of samples without high-pressure treatments to be predicted. SIGNIFICANCE AND IMPACT OF THE STUDY: High-pressure processing seems more appropriate for new types of salmon products than for a classical product like CSS where consumers expect specific quality attributes.

Animals↗

Effects of a microbial probiotic (Sporolactobacillus P 44) on postprandial porto-arterial concentration differences of glucose, galactose and amino-nitrogen in the growing pig.

Postprandial kinetics of porto-arterial concentration differences of glucose (G), galactose (Gal), L-lactic acid (LA), amino-nitrogen (AN) and urea (U) were studied in the pig after the ingestion of 10(7) colony-forming units (cfu) of Sporolactobacillus P 44 per g of feed. Eight fistulated pigs (portal vein and brachiocephalic trunk; mean body weight 70 +/- 4 kg) were used. The diet was based on skimmed milk (32%), barley (30%), maize (10%) and lactose (7%). The postprandial blood kinetics, 4 conducted per animal at 1-wk intervals, were studied during the 3 h following the ingestion of test meals of 1,000 g basal diet (BD) or the same diet supplemented by the bacteria (SD). The apparent absorption was estimated from the area between the portal and arterial concentrations. The areas of porto-arterial differences of G, Gal and AN of SD for the first 3 h after the meal were significantly higher after SD ingestion than those measured after BD intake. Plasma concentrations of U and porto-arterial differences of U and LA were not modified by the probiotic. These effects disappeared immediately after dietary supplement interruption, suggesting that added bacteria presence in the intestinal lumen was fundamental to the modifications observed in apparent absorption.

Animal Feed↗

Identification and characterization of Carnobacteria isolated from fish intestine.

Eleven bacterial strains were isolated from the gastrointestinal tract of four fish species, Atlantic salmon (Salmo salar L.), Arctic charr (Salvelinus alpinus L.), Atlantic cod (Gadus morhua L.) and wolffish (Anarhichas lupus L.). All the strains were Gram-positive rods, non-sporing, catalase and oxidase-negative, able to grow at pH 9.0 but not on acetate containing media (pH < or = 5.4), and were fermentative. They had a high content of oleic acid (18:1 n-9) in cellular lipid, and were found to belong to the genus Carnobacterium by phenotypic criteria. The eleven carnobacteria strains were further identified on the basis of 16S rDNA sequence analysis and AFLP(TM) fingerprinting.

Aeromonas↗

Whole-organism fingerprinting of the genus Carnobacterium using Fourier transform infrared spectroscopy (FT-IR).

Sixty seven strains of Carnobacterium, atypical Lactobacillus, Enterococcus durans, Lactobacillus maltaromicus and Vagacoccus salmoninarum were examined by Fourier transform infrared (FT-IR) spectroscopy. The effects of culture age and reproducibility over a six month period were also investigated. The results were analysed by multivariate statistics and compared with those from a previous numerical phenetic study, a pyrolysis mass spectrometry (PyMS) study and with investigations which used DNA-DNA and 16S rRNA sequencing homologies. Taxonomic correlations were observed between the FT-IR data and these studies. Culture age was observed to have little effect on the spectra obtained. The reproducibility study indicated that there was correlation between spectra produced on two occasions over the six month period. It was concluded that FTIR is a reliable method for investigating carnobacterial classification, and may have further potential as a rapid method for use in Carnobacterium identification.

Food Microbiology↗

ClaI. a new restriction endonuclease from Caryophanon latum L.

From Caryophanon latum L site specific restriction endonuclease (ClaI) has been purified, which recognises tha DNA hexanucleotide palindrome 5'-A-T-C-G-A-T-3'. Staggered cleavage generates DNA restriction fragments with 5'-terminal pCG extensions. A CLaI map of bacteriophage lambda has been determined, which indicates cleavage inhibition due to adenine methylation at over lapping ClaI-GATC recognition sequences. Plasmid pBR322 is cut only once, in the tetracycline promoter region, and can, therefore, be used as a vector system for cloning fragments derived from ClaI digestions, and in addition for fragments generated by TaqI, HpaII, and several other enzymes.

Bacteriophage lambda↗

High incidence of Alloiococcus otitis in otitis media with effusion.

BACKGROUND: The etiology of otitis media with effusion (OME) is unclear. Although the majority of effusions show inflammation, culture methods yield positive results for bacteria in only 20 to 30% of cases. METHODS: The polymerase chain reaction was used for detection of three upper respiratory tract pathogens, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae, and a fairly recently described bacterium, Alloiococcus otitis (A. otitidis), that is solely found in OME. The study included 67 middle ear effusions that were collected from 48 pediatric OME patients during ventilation tube placement. RESULTS: PCR tested positive for 57 (85.1%) of the middle ear effusions. Thirty-one (46.3%) A. otitis-, 12 (17.9%) H. influenzae-, 25 (37.3%) M. catarrhalis- and 14 (20.9%) S. pneumoniae-positive effusions were obtained. All four study organisms showed similar distribution in effusions of various duration (P = 0.72) and in different effusion types (P = 0.59). Only the proportion of M. catarrhalis-positive effusions was lowered by recent antimicrobial therapy (P < 0.05). Although the study organisms had equal distributions among singly and multiply positive specimens (P = 0.90), A. otitis was detected significantly more often with one of the three other species (15 of 19, 78.9%) than the other species with each other (4 of 19, 21.1%, P < 0.001). CONCLUSIONS: The findings suggest a bacterial etiology for OME. Association of A. otitis with the three other species implies that this organism might have the capability of augmenting bacterial colonization in the middle ear.

Child↗

Preventative effects of lactulose in the trinitrobenzenesulphonic acid model of rat colitis.

AIMS: Lactulose is a drug used as a laxative that has been shown to promote the growth of lactobacilli and bifidobacteria, acting as a prebiotic and with a potential beneficial effect in inflammatory bowel disease. The present study describes the preventive antiinflammatory activity of lactulose in the trinitrobenzenesulphonic acid (TNBS) model of rat colitis. METHODS: Rats were rendered colitic by a colonic instillation of 10 mg of TNBS dissolved in 0.25 mL of 50% ethanol. One group of colitic rats received lactulose, which was incorporated in the drinking water (2.5% wt/vol) for 2 weeks before TNBS instillation, and colonic damage was evaluated 1 week after colitis induction. Different biochemical markers of colonic inflammation were assayed: myeloperoxidase activity, glutathione content, tumor necrosis factor alpha, leukotriene B4 levels, and colonic inducible nitric oxide synthase expression. In addition, bacterial counts (for lactobacilli and bifidobacteria) were performed in colonic contents from colitic rats. RESULTS: The results show that lactulose exerted a preventive antiinflammatory effect in this model of rat colitis, as evidenced by a significant reduction of myeloperoxidase activity and by a decrease of both colonic tumor necrosis factor alpha and leukotriene B4 production. This effect was also characterized by an inhibition of colonic inducible nitric oxide synthase expression, which is unregulated as a consequence of the inflammatory status. This beneficial effect was associated with increased levels of lactobacilli and bifidobacteria species in colonic contents in comparison with untreated colitic rats. CONCLUSION: In conclusion, the intestinal antiinflammatory effect of lactulose could be related to its prebiotic properties, supporting its potential use in human inflammatory bowel disease.

Animals↗

Comparison of partial malolactic enzyme gene sequences for phylogenetic analysis of some lactic acid bacteria species and relationships with the malic enzyme.

DNA sequences covering 36% of the mle gene that encodes the malolactic enzyme were determined for 13 strains of lactic acid bacteria, representing Pediococcus, Leuconostoc, Lactobacillus and Oenococcus genera. The sequences were aligned with the corresponding region of mleS in Lactococcus lactis. The phylogenetic distance matrix tree of all mle sequences was compared with the 16S rRNA phylogenetic tree. The analysis showed that the mle fragment evolved more rapidly than the 16S gene and differently. Pediococcus and Lactobacillus species were intermixed in the 16S rRNA tree whereas they were separated in the mle tree. Leuconostoc mesenteroides and Oenococcus oeni were distinct from other species in the 16S rRNA tree, whereas they were intermixed with Lactobacillus species and Lactococcus lactis in the mle tree. The amino acid sequences deduced from partial mle genes were aligned with 22 malic enzyme sequences and the corresponding phylogenetic tree was constructed. Malic and malolactic enzymes were distinct at the phylogenetic level, except for malic enzymes of yeast and Escherichia coli which were nearer the malolactic enzymes than the other malic enzymes. The analysis of conserved sites showed several interesting amino acids specific to either malic enzyme or malolactic enzyme.

Amino Acid Sequence↗

Carnobacterium inhibens sp. nov., isolated from the intestine of Atlantic salmon (Salmo salar).

Strain K1T, isolated from the gastrointestinal tract of Atlantic salmon (Salmo salar), has the capacity to inhibit the growth of the fish pathogens Vibrio anguillarum and Aeromonas salmonicida. Strain K1T is a motile Gram-positive psychrophilic rod that lacks both catalase and oxidase, which does not grow on acetate containing media, but grows at pH 9 and in TSB with up to 6% sodium chloride content. Strain K1T is facultatively anaerobic and tryptone as a sole source of nutrient promotes growth. The most abundant cellular fatty acid of strain K1T is oleic acid (18:1cis9). Based on 16S rDNA sequence comparisons, it is suggested that strain K1T is phylogenetically closely related to C. alterfunditum. However, the unique phenotypic attributes of strain K1T suggest that it represents a new species. The name Carnobacterium inhibens is proposed, for which the type strain is K1T (= CCUG 31728T).

Aeromonas↗

Description of Paralactobacillus selangorensis gen. nov., sp. nov., a new lactic acid bacterium isolated from chili bo, a Malaysian food ingredient.

Paralactobacillus selangorensis gen. nov., sp. nov. is described. This organism, isolated from a Malaysian food ingredient called chili bo, is an obligatory homofermentative, rod-shaped lactic acid bacterium. The G+C content is 46.1-46.2+/-0.3 mol%. Earlier 16S rRNA studies showed that this organism constitutes a new taxon distantly related to the Lactobacillus casei-Pediococcus group. A phenotypic description that distinguishes Paralactobacillus selangorensis from other genera of lactic acid bacteria is presented. The type strain of Paralactobacillus selangorensis is LMG 17710T.

Acetic Acid↗

Alkalibacterium olivoapovliticus gen. nov., sp. nov., a new obligately alkaliphilic bacterium isolated from edible-olive wash-waters.

A novel Gram-positive, obligately alkaliphilic, non-sporulating, rod-shaped, flagellated bacterium is described. Three different strains of the bacterium were isolated from the wash-waters of edible-olive production. The strains are motile, psychrotolerant, halotolerant, facultatively anaerobic bacteria with a pH optimum of 9.0-9.4 for two strains and 9.8-10.2 for the third. They are catalase- and oxidase-negative. A range of hexoses and some disaccharides composed of hexoses, but not pentoses are metabolized by the bacterial strains: D(+)-glucose, D(+)-glucose 6-phosphate, D(+)-cellobiose, starch or sucrose are the carbohydrates best utilized. No common amino acids are utilized by the three alkaliphilic strains, but yeast extract can serve as sole carbon and energy source. The major membrane phospholipids are diphosphatidylglycerol, phosphatidylglycerol and an unknown phospholipid, all containing saturated and unsaturated, even-carbon-numbered fatty acyl chains with hexadecanoic and hexadecen(7)oic as the predominant components. The G+C content of the DNA in all three strains is 39.7+/-1.0 mol% and the DNA relatedness by hybridization is >88% for all pairings of the three strains. The results of 16S rRNA sequence comparisons revealed that the strains represent a new alkaliphilic linkage in the order Bacillales, belonging to the Carnobacterium/Aerococcus-like spectrum. It is proposed that the strains should be assigned to a new genus and species, Alkalibacterium olivoapovliticus. The three strains, designated WW2-SN4aT, WW2-SN4c and WW2-SN5, have been deposited with Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ) as DSM 13175T, DSM 12937 and DSM 12938 respectively, and in the National Collection of Industrial and Marine Bacteria as NCIMB 13710T, NCIMB 13711 and NCIMB 13712, respectively. The type species of this genus is Alkalibacterium olivoapovliticus and the type strain is WW2-SN4aT.

Anaerobiosis↗

Translocation of indigenous microflora in an experimental model of sepsis.

Translocation of viable bacteria from gut to bloodstream and other sterile body sites during shock has been demonstrated in several experimental and clinical studies. The factors causing translocation and its incidence at different stages of shock are not known. The aim of the study was to evaluate the importance of several factors causing translocation of indigenous microflora in an experimental model of septic shock based on intraperitoneal Escherichia coli sepsis in rats. Counts of inoculated E. coli and translocated bacteria in different locations, gut morphology and haematological values were evaluated at different stages of sepsis. Sepsis developed in all animals and E. coli achieved the highest counts in blood 6 h after inoculation. Translocation was commonest at 6 and 12 h after inoculation. Frequently translocating bacteria were lactobacilli, bifidobacteria, bacteroides and peptostreptococci. In early sepsis, translocation was associated with high E. coli counts in blood, yet in late sepsis the opposite correlation was present. Low infiltration by neutrophils in the ileum and decreased mitotic activity in the colon were associated with a high translocation rate. In early sepsis, translocation was associated with low lymphocyte counts, but in late sepsis, with low neutrophil counts. Translocation of bacteria (including anaerobes) that colonise the gut in high counts takes place during sepsis. Putative influencing factors such as activity of the primary disease (bacterial counts in blood), gut morphology or haematological values seem to have different impacts on translocation, depending on the stage of the disease.

Animals↗

Modulation of genotoxic enzyme activities by non-digestible oligosaccharide metabolism in in-vitro human gut bacterial ecosystems.

Supplementation of the human diet with prebiotic substances such as inulin and non-digestible oligosaccharides (NDO), e.g., galacto-oligosaccharides (GOS), has been associated with various health benefits. However, little information is available regarding the spatial location of their metabolism in human gut bacterial ecosystems. Therefore, the present study investigated the metabolism of inulin and GOS with respect to bacterial growth, bifidobacterial stimulatory properties and anti-mutagenicity potential, in a three-stage continuous culture model of the colon which reproduces the physicochemical characteristics of the proximal (V1) and distal (V2, V3) colons. Fermentation of both carbohydrates was rapid, and occurred primarily in V1, as evidenced by acid formation. Inulin metabolism was associated with 10-fold stimulation of lactobacillus populations, together with smaller increases in bifidobacterial cell counts in V1. However, peptostreptococci, enterococci and Clostridium perfringens also increased in this fermentation vessel. In contrast, GOS was only weakly bifidogenic in V1, although these bacteria did proliferate in V2. GOS also increased lactobacilli by an order of magnitude in V1. However, overall changes in microbial populations resulting from inulin or GOS addition were minimal in V2 and V3. Potential beneficial effects of inulin metabolism included minor reductions in beta-glucosidase and beta-glucuronidase, whereas GOS strongly suppressed these enzymes, together with arylsulphatase (AS). Growth of putatively health promoting micro-organisms was not only associated with reductions in enzymes linked to genotoxicity. For example, both carbohydrates stimulated synthesis of nitroreductase and azoreductase, throughout the fermentation system, while inulin increased AS. Colonic transit time is an important factor in bacterial metabolism in the large bowel, and these data suggest that, in some circumstances, NDO fermentation will occurprincipally in the proximal colon.

Adult↗

Nucleic acid relatedness studies on the genus Carnobacterium and related taxa.

None of the species Carnobacterium piscicola, C. divergens, C. mobile or C. gallinarum showed significant DNA-DNA homology between themselves and other lactic acid bacteria [corrected]. Nevertheless, the Carnobacterium species were found to belong to the same ribosomal RNA homology cluster. The species in this cluster were distant from the other bacteria tested.

Bacteria↗

Divercin V41, a new bacteriocin with two disulphide bonds produced by Carnobacterium divergens V41: primary structure and genomic organization.

Divercin V41 is a new bacteriocin produced by Carnobacterium divergens V41, a lactic acid bacterium isolated from fish viscera. The amino acid sequence of divercin V41 showed high homologies with pediocin PA-1 and enterocin A. Two disulphide bonds were present in the hydrophilic N-terminal domain and in the highly variable hydrophobic C-terminal domain, respectively. A DNA probe designed from the N-terminal sequence of the purified peptide was used to locate the structural gene of divercin V41. A 6 kb chromosomal fragment containing the divercin V41 structural gene (dvnA) was cloned and sequenced. The results indicate that divercin V41 is synthesized as a pre-bacteriocin of 66 amino acids. The 23-residue N-terminal extension is cleaved off to yield the mature 43-amino-acid divercin V41. In addition, the fragment encodes putative proteins commonly found within bacteriocin operons, including an ATP-dependent transporter, two immunity-like proteins and the two components of a lantibiotic-type signal-transducing system. The genetic organization of the fragment suggested important gene rearrangements.

Amino Acid Sequence↗

Characterization of the genetic locus responsible for production and immunity of carnobacteriocin A: the immunity gene confers cross-protection to enterocin B.

Carnobacteriocin A (CbnA) is a regulated bacteriocin produced by Carnobacterium piscicola LV17A that is encoded on a 72 kb plasmid. A 10.0 kb fragment from this plasmid that contained information necessary for bacteriocin production and immunity was cloned and sequenced. Genetic analysis showed the presence of the previously sequenced structural gene for CbnA, as well as genes encoding proteins homologous to dedicated bacteriocin transport proteins and proteins of three-component signal transduction systems. The induction factor (CbnX) was chemically synthesized and induced CbnA production at 10(-11) M or higher in a C. piscicola LV17A culture that had lost the ability to produce bacteriocin as a result of dilution. The gene cbiA for the immunity protein is not located in typical close proximity to the structural gene for CbnA and is encoded in the opposite orientation. CbiA has homology with EniB, the immunity protein for enterocin B that is also encoded in the opposite orientation to the bacteriocin gene. CbiA and EniB cross-protected against the corresponding bacteriocins.

Amino Acid Sequence↗