Biomedical subjects

Virginia S Ocaña

Publications and source records attributed to Virginia S Ocaña.

5 recordsLinked to original sources

PubMed2004

Production of antimicrobial substances by lactic acid bacteria II: screening bacteriocin-producing strains with probiotic purposes and characterization of a Lactobacillus bacteriocin.

Bacteriocins have been defined as proteinaceous, bactericidal substances synthesized by bacteria, which usually have a narrow spectrum of activity, only inhibiting strains of the same or closely related species. The term bacteriocin-like substance is applied to antagonistic substances that are not completely defined or do not fit the typical criteria of bacteriocins. They have been reported to inhibit a wide range of both Gram-positive and Gram-negative bacteria as well as fungi. Lactobacillus species are the dominant microorganisms isolated from the vagina of healthy premenopausal women. In this environment, they exert a protective effect against pathogenic microorganisms by different mechanisms such as production of antimicrobial agents, which include organic acids, hydrogen peroxide, and probably bacteriocins. The production of bacteriocins by vaginal lactobacilli has been demonstrated in vitro; however, it is not yet well established whether they are produced in vivo as another antagonistic mechanism exerted by the normal microflora.Bacteriocin-producing bacteria as well as bacteriocins per se are of growing interest as biological controls in the manufacture of beverages and fermented products, mainly in the area of dairy products. These bacteria have also been proposed as probiotic candidates for human or animal use. The objectives of the present chapter are to describe the methods employed for: 1. Detection of production of bacteriocins among vaginal Lactobacillus strains. 2. Characterization of the bacteriocin or bacteriocin-like substances. 3. Study of the kinetics of production and mode of action of bacteriocins. 4. Determination of the inhibition of pathogenic microorganisms by bacteriocin-producing strains in mixed cultures.

Anti-Infective Agents↗

PubMed2004

Bacterial surface characteristics applied to selection of probiotic microorganisms.

For the study of probiotic microorganisms, the in vitro selection tests need to be based on a solid scientific foundation. Surface characteristics, one of the in vitro properties are used to evaluate the potentially probiotic strains of lactobacilli. Bacterial surface properties have been associated with attachment to a variety of substrata. Bacterial adhesion to tissues is considered the first step, and such adhesion can also determine the colonization capability of a microorganism. Through adhesion ability and colonization of tissues, probiotic microorganisms can prevent pathogen access by steric interactions or specific blockage on cell receptors. One of the main characteristics studied is the hydrophobic nature of the bacterial cell surface. To test this property, Rosenberg and Doyle divided microbial cell hydrophobicity assays into two categories. The first includes contact angle measurements (CAMs), partitioning of cells into one or another liquid phase (TTP), and adsorption of individual hydrophobic molecular probes at the cell surface. The second category includes microbial adhesion to hydrocarbons (MATH), hydrophobic interaction chromatography (HIC), and adhesion to polystyrene and other hydrophobic solid surfaces. The tests included in the first category measure hydrophobic properties of the outer cell surface as a whole; those in the second measure hydrophobicity in terms of adhesion. Finally, those bacterium classified as hydrophobic can be considered as able to mediate adhesion. The objective of this chapter is to describe three different methods applied in our laboratory for the study of bacterial surface properties. They can be used to screen characteristics of lactobacillus strains for probiotic purposes. They are: Microbial adhesion to hydrocarbons (MATH); Salt aggregation test (SAT); Hemagglutination (HA) reaction.

Animals↗

PubMed2004

Adhesion ability of Lactobacillus to vaginal epithelial cells: study by microbiological methods.

Adhesion of lactobacilli to the epithelium has been described as the first step in the formation of a barrier to prevent undesirable microbial colonization; consequently, it has been defined as a characteristic of interest for selecting probiotic strains. Several methods have been described to predict the adhesion ability of Lactobacillus. Early studies were phenomenological: it was useful to determine whether a particular bacterium could hemagglutinate, or bind to coated particles. Later, studies based on the adhesion of bacteria to epithelial cells in vitro were developed. These last assays were based on the numbers of bacteria attached to epithelial cells, which were determined by counting stained microorganisms under light microscopy or by measuring the radioactivity of previously radiolabeled bacteria. Because the microscope technique, had some disadvantages, a modification was developed in our laboratory. The technique described in this chapter is a modification of the Mardh and Weströn method. The method allows the study of the adhesion ability of bacteria, even if they are aggregating or if they are high-adherent bacteria covering a large area of the epithelial cell surface. Determination of the number of adherent bacteria by counting colonies grown in a selective media avoids the time-consuming, tedious, and hazardous counting under the light microscope and the use of radioactive methods.

Animals↗

PubMed2003

Growth and lactic acid production by vaginal Lactobacillus acidophilus CRL 1259, and inhibition of uropathogenic Escherichia coli.

Lactic acid-producing lactobacilli were selected from 134 human vaginal isolates by testing their capability to inhibit the growth of different pathogenic micro-organisms. Lactobacillus acidophilus CRL 1259 (from the CERELA Culture Collection) was selected to study the effects of temperature, pH and culture medium on growth and lactic acid production. Growth parameters were estimated by using the model of Gompertz. Kinetics of inhibition of uropathogenic Escherichia coli were evaluated in mixed cultures of the pathogen and L. acidophilus. Optimal conditions for growth and lactic acid production by L. acidophilus were pH 6.5 or 8.0 and 37 degrees C. Under these conditions, growth was higher in LAPTg (yeast extract/peptone/tryptone/Tween 80/glucose) broth than in MRS (De Man-Rogosa-Sharpe) broth. However, lactic acid production was more efficient in MRS broth. Under optimal conditions for lactic acid production, L. acidophilus inhibited the growth of E. coli. These results suggest that inclusion of L. acidophilus CRL 1259 in probiotic products for vaginal application would be beneficial.

Adult↗

PubMed2002

Vaginal lactobacilli: self- and co-aggregating ability.

Lactic acid bacteria are the dominant bacteria of the vaginal tract in healthy women. Lactobacillus species form a barrier population that protects from pathogen colonisation by mechanisms that include adhesion to epithelial surfaces, self-aggregation and co-aggregation. In this study, factors involved in the self-aggregating ability of vaginal lactobacilli and in the co-aggregation of these microorganisms with Candida spp. are studied. Both self-aggregation and co-aggregation are monitored quantitatively by the decrease in the absorbance of suspensions of the microorganisms and qualitatively by light microscopy. The self-aggregating ability of four vaginal lactobacilli was shown to be caused by a peptide or protein sensitive to trypsin. However, in self-aggregating Lactobacillus acidophilus CRL 1294 the factor was resistant to trypsin and sensitive to pepsin. Among self-aggregating lactobacilli, L. acidophilus CRL 1294 and L. salivarius CRL 1328 were able to co-aggregate with Candida spp. The co-aggregating factor for both strains proved to be peptide of the surface and a peptide on the bacterial surface, while the receptor on the yeast was a carbohydrate. Co-aggregation of both lactobacilli and Candida spp. was inhibited by the addition of mannose but was not affected by other carbohydrates. Self and co-aggregation factors were not able to induce aggregation in non-aggregating lactobacilli.

Bacterial Adhesion↗