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Carbon dioxide stimulates the production of amylovorin L by Lactobacillus amylovorus DCE 471, while enhanced aeration causes biphasic kinetics of growth and bacteriocin production.

The effects of both oxygen and carbon dioxide on growth of and product formation by Lactobacillus amylovorus DCE 471, a promising new sourdough starter culture, were assessed through controlled, in vitro fermentation experiments, using a temperature of 37 degrees C and a constant pH of 5.4. It was seen that aeration affected both cell growth and amylovorin L production. At aeration rates of 1 l min(-1) and more, the bacterial population was subjected to oxidative stress as reflected by biphasic growth patterns. During the first growth phase, the maximum specific growth rate increased with increasing aeration rates stabilizing at the highest oxygen concentrations. The maximum obtainable cell yields decreased. During the second growth phase, the amylovorin L production was stimulated at the highest aeration. However, amylovorin titers were never higher in the presence of oxygen compared with the anaerobic fermentations. Carbon dioxide did not influence cell growth of L. amylovorus DCE 471. The maximum specific growth rate and the biomass concentrations were merely affected. On the other hand, the maximum soluble bacteriocin titers coincided with the highest carbon dioxide flow rates. These results indicate that mild aeration of type II sourdoughs might enhance both cell yield and amylovorin L production by L. amylovorus DCE 471, thereby contributing to the competitiveness of the strain. Growth in an ecosystem together with yeasts producing carbon dioxide might exert a positive effect on the production of amylovorin L as well.

Bacteriocins↗

Sugars relevant for sourdough fermentation stimulate growth of and bacteriocin production by Lactobacillus amylovorus DCE 471.

The effects of sugars relevant for sourdough fermentation (i.e. glucose, fructose, maltose, and sucrose) on the kinetics of the bacteriocin-producing Lactobacillus amylovorus DCE 471 strain were assessed. The sugars were applied solely or in combination in a sourdough simulation medium during batch fermentations at temperature and pH conditions encountered during the production of type II sourdoughs. When growing on a single energy source, glucose was preferentially consumed by L. amylovorus DCE 471, followed by maltose and fructose. The strain was unable to grow on sucrose. In glucose-containing mixtures, glucose was always consumed most rapidly by L. amylovorus DCE 471 and seemed to steer its growth during the early growth phase, mainly because of the delaying effect on maltose consumption. Maltose consumption started only when low glucose levels were reached. In all cases, fructose was used as an energy source and not as a terminal electron acceptor, since no acetic acid or mannitol were produced. Increased bacteriocin titres were observed with binary or ternary sugar combinations compared to single energy sources. Thus, the diversity of the energy source seemed to stimulate the production of amylovorin L. Cell growth of and production of amylovorin L by L. amylovorus DCE 471 paralleled for all sugar combinations tested.

Bacteriocins↗

Lactobacillus endocarditis: case report and review of cases reported since 1992.

Lactobacillus is a rare cause of endocarditis with only 78 reported cases in the literature. We report a case of Lactobacillus endocarditis and review reported adult cases since the introduction of the Duke's criteria for endocarditis. An analysis is presented with a focus on outcomes. Mortality from reported cases of Lactobacillus endocarditis was found to have substantially improved since 1992. Surgical rates for persistent disease remain the same. Possible reasons for this improvement include better antibiotics, earlier recognition of cases, and more aggressive treatment regimens.

Bacteremia↗

Enumeration of specific bacterial populations in complex intestinal communities using quantitative PCR based on the chaperonin-60 target.

We used qPCR and the target gene chaperonin-60 (cpn60) to enumerate Clostridium perfringens genomes in DNA extracts from contents of the chicken gastrointestinal tract with the aim of optimizing this methodology to enumerate any bacterium of interest. To determine the most accurate protocols for determining target species abundance, we compared various DNA extraction methods in combination with four methods for producing standard curves. Factors affecting accuracy included the co-purification of PCR inhibitors and/or fluorescence quenchers and the yield of target DNA in the extract. Anion exchange chromatography of the spiked test samples enabled accurate enumeration of C. perfringens using a standard curve comprised of a plasmid containing a fragment of C. perfringens cpn60. We used qPCR to enumerate C. perfringens and other intestinal bacteria in ileum and cecum samples from chickens that had been challenged with C. perfringens and compared the results with viable counts on corresponding selective agars. We conclude that qPCR-based molecular enumeration of target species in the gastrointestinal tract is feasible, but care must be taken in order to mitigate the effects of confounding factors that can affect the apparent cell count.

Animals↗

Inhibition of allergen-induced airway inflammation and hyperreactivity by recombinant lactic-acid bacteria.

Recombinant lactic-acid bacteria (LAB) are able to inhibit allergen-specific T-cell responses. In this study, we examined whether oral feeding of recombinant LAB was able to suppress allergen-induced airway inflammation and hyperreactivity (AHR) in a murine model. Animals were intraperitoneally sensitized with Dermatophagoides pteronyssinus group-5 allergen (Der p 5) and orally treated with recombinant LAB containing a plasmid-encoded Der p 5 gene or placebo on day 7 and day 14 for three days consecutively. Twenty-one days after sensitization, mice underwent inhalational challenging. Der p 5-specific immunological responses including changes to specific immunoglobulin G and E (IgE) levels, the presence of cells in the bronchoalveolar lavage fluid (BALF), and AHR were assessed following this inhalational challenge. We demonstrated that oral feeding of recombinant LAB could significantly decrease the synthesis of Der p 5-specific IgE, and AHR. Furthermore, following such treatment, we also noted that both neutrophils and eosinophils had infiltrated the BALF to a significantly lower extent, when compared to the vehicle-treated group. Neither recombinant allergen nor LAB alone was able to suppress allergen-induced immune responses. Our findings suggest that treatment with recombinant LAB at a low dose can suppress allergen-induced airway allergic inflammation, this providing a basis for developing a novel therapeutic method for allergic airway diseases.

Administration, Oral↗

In vitro inhibition of Eimeria tenella invasion by indigenous chicken Lactobacillus species.

The aim of this study was to determine the effects of indigenous chicken Lactobacillus species isolates from different parts of the gastrointestinal tract on Eimeria tenella invasion in vitro and to characterise the nature of inhibition, if any. The effects of competitive exclusion, steric interference and bacterial extracellular factors on E. tenella invasion were examined in an MDBK cell model. Several Lactobacillus species were initially isolated from chickens and identified by biochemical characteristics and 16S-rRNA. All Lactobacillus species isolates tested, significantly inhibited E. tenella invasion. Steric interference did not affect parasite invasion. Extracellular metabolic factors secreted by Lactobacillus species isolates into the surrounding media were shown to inhibit parasite invasion and these factors appeared to be heat stable. These results show that the natural microflora of poultry can provide a source of E. tenella-inhibiting Lactobacillus species in vitro, and thus may contribute to the control of Eimeria infection.

Animals↗

[Submental abscess by Lactobacillus acidophilus/jensenii].

The different species of Lactobacillus genus are bacteria of a low pathogenicity. They are found in the gastrointestinal tract, the female genitourinary tract, and also as part of the anaerobic flora in the mouth. Due to this low pathogenicity, they are generally related with infections together with other with more virulent microorganisms, or in immunocompromised patients. In our case, Lactobacillus appears alone as an etiological agent in an immunocompetent patient with a submental abscess.

Abscess↗

Effect of sodium chloride on growth and bacteriocin production by Lactobacillus amylovorus DCE 471.

A kinetic investigation of the effect of sodium chloride on cell growth of Lactobacillus amylovorus DCE 471 and amylovorin L471 production was carried out through in vitro experiments using a temperature and pH prevailing during sourdough fermentations. Sodium chloride interfered both with cell growth and bacteriocin production. Biomass formation and amylovorin L471 production decreased in the presence of increasing salt concentrations. Maximum bacteriocin activities were observed after the addition of 10 g l(-1) of NaCl, while the maximum specific growth rate reached an optimum at 5 g l(-1) of NaCl. High salt concentrations (20-40 g l(-1)) resulted in biphasic fermentation profiles. Based on these results, incorporation of 5-10 g l(-1) of sodium chloride in the water phase of type II sourdough preparations might be beneficial to enhance bacterial growth and amylovorin L471 production, and so contribute to the competitiveness of the strain in a sourdough environment.

Bacteriocins↗

Probiotic bacteria: safety, functional and technological properties.

During the past two decades probiotic (health promoting) micro-organisms have been increasingly included in various types of food products, especially in fermented milks. Several aspects, including safety, functional and technological characteristics, have to be taken into consideration in the selection process of probiotic micro-organisms. Safety aspects include specifications such as origin (healthy human GI-tract), non-pathogenicity and antibiotic resistance characteristics. Functional aspects include viability and persistence in the GI-tract, immunomodulation, antagonistic and antimutagenic properties. Before probiotic strains, chosen on the basis of their good safety and functional characteristics, can benefit the consumer, they must first be able to be manufactured under industrial conditions. Furthermore, they have to survive and retain their functionality during storage, and also in the foods into which they are incorporated without producing off-flavours. Factors related to the technological and sensory aspects of probiotic food production are of utmost importance since only by satisfying the demands of the consumer can the food industry succeed in promoting the consumption of functional probiotic products in the future.

Administration, Oral↗

In vivo distribution of particulate antigens and liposomes in murine spleen. A possible role in the humoral immune response.

Several particulate antigens and liposomes were intravenously injected in mice in order to study their localization patterns in spleen and liver. Liposomes have been proposed as promising carriers for haptens and antigens. It was studied whether the phospholipid composition, cholesterol content and charge of the liposomes played a role in their distribution within the spleen. Different thymus-independent type 1 and type 2 and thymus-dependent particulate antigens as well as liposomes were labeled with the lipophilic fluorochrome Di-I. After labeling they were intravenously injected and spleens and livers were removed at different time intervals and prepared for light- and fluorescence-microscopy. We have observed that all particulate antigens and liposomes administered to the mice localized according to the same distribution pattern in the spleen. After 2 and 4 h particles were located in macrophages of the marginal zone and after 24 h white pulp macrophages had also ingested particulate antigens and liposomes. So we conclude that the distribution of the particulate antigens and liposomes in the spleen is independent of the immunological nature of the particles. Results are discussed with respect to the question whether or not the distribution of particulate antigens and liposome associated antigens or haptens, may be a crucial factor in determining the type of immune response to be elicited.

Animals↗