Biomedical subjects

María Elena Nader-Macías

Publications and source records attributed to María Elena Nader-Macías.

17 recordsLinked to original sources

PubMed2006

Aryloxoalcanoic compounds induce resistance to antibiotic therapy in urinary tract infection caused by Escherichia coli.

Clofibric acid (CL) is a compound used to control hypertriglyceridemia, and ethacrynic acid (ET) is administered to enhance diuresis. These compounds are structurally analogous to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), as they have a chlorinated phenoxy moiety. As these agents are mainly excreted by the renal route, they could potentially coexist with Escherichia coli in the urinary tract of infected patients. Induction of the in vitro resistance of E. coli to hydrophilic antibiotics was determined by increasing the values of the minimum inhibitory concentration (2-40-fold). These results correlated with drastically inhibited expression of the hydrophilic bacterial channel OmpF. In vivo assays were performed in ascending urinary tract infection in female BALB/c mice. Treatment with the hydrophilic antibiotic cephalexin 25 mg kg(-1) day(-1) by the oral route diminished renal infection. The CFU mean values in the kidneys were between 75% and 89% lower than those in animals without treatment. Simultaneous exposure to CL (at a therapeutic dose, 28.6 mg kg(-1) day(-1)) did not change the effect of the treatment. In contrast, ET at 2.9 mg kg(-1) day(-1) or 2,4-D at 70 mg kg(-1) day(-1) inhibited the antibiotic therapeutic effect. Moreover, 2,4-D dramatically increased bacterial infection after 9 days of exposure.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2004

Clofibric and ethacrynic acids prevent experimental pyelonephritis by Escherichia coli in mice.

Interfering Escherichia coli attachment to the urinary tract, using P-fimbriation inhibitors, can prevent pyelonephritis. Clofibric and ethacrynic acids are organic compounds structurally related, but with different pharmacological uses. These agents are potentially active in the urinary tract due to its elimination in an unaltered form by the renal route. This study described a pyelonephritogenic E. coli strain, grown in the presence of sub-inhibitory concentrations of clofibric or ethacrynic acids (0.1 and 1 mM, respectively), which exhibits inhibition of P1 erythrocytes agglutination and a drastic decrease in fimbriation, using electron microscopy and quantitative analyses of superficial proteins (decrease to a 17-25% in comparison with the control). In vivo assays were performed using ascending urinary tract infection in mice. The treatment with therapeutic doses of the drugs, administered 2 days before the bacterial challenge and daily until the end of the experiment (22 days), abolished renal infection after 7-10 days of drug exposure. Within this period clofibric acid did not produce adverse effects on the renal parenchyma. However, ethacrynic acid caused pyelitis and tubular cellular desquamation. These results suggested that clofibric acid might be useful in the short-term prophylaxis of urinary tract infection.

Animals↗

PubMed2004

Effect of Ampicillin on the kinetics of colonization of Streptococcus pneumoniae and Lactobacillus fermentum in the respiratory tract of mice.

Ampicillin was selected to further study the effect of this antibiotic on the colonization capability of S. pneumoniae and L. fermentum intranasally inoculated in a mice experimental model. The sensitivity of S. pneumoniae and L. fermentum to antibiotics was evaluated by different "in vitro" techniques. The results showed that both microorganisms have a typical pattern of sensitivity to antibiotics in these assays. The "in vivo" experiments showed that the treatment with Ampicillin increased the number of lactobacilli and neumococci in the groups of mice treated only with one of the microorganisms. In those mice treated with Lactobacillus, challenged later with neumococci and treated with Ampicillin, the pathogen in lung decreased on the 4th day, disappearing completely after on. The histological studies showed that the antibiotic treatment decreased the inflammatory response produced by the pathogen at the lung and trachea levels.

Journal Article↗

PubMed2004

Viability of vaginal probiotic lactobacilli during refrigerated and frozen storage.

The viability of six different strains of probiotic vaginal Lactobacillus was examined in two different cryoprotective media, during refrigerated versus frozen storage, and using two traditional types of stock cultures for starting the biomass production. Freezing at -20 degrees C and -70 degrees C had much less adverse effect on viability than did storage at 7 degrees C, and the reduction in viability was greater at -20 degrees C than at -70 degrees C. The strains showed variation in the extent of the viability losses during both types of storage. Milk-yeast extract (MYE) was shown to be the more suitable protective medium to maintain viability of the strains during the storage. The vaginal Lactobacillus strains are most stable in MYE at -70 degrees C with only a small decrease of the viability observed under these conditions. The viable cell counts of Lactobacillus paracasei CRL 1251 and CRL 1289, L. crispatus CRL 1266 and L. salivarius CRL 1328 remained around 1 x 10(8) CFU/mL after 24 months of storage at -70 degrees C, or up to 18 months for L. acidophilus CRL 1259.

Journal Article↗

PubMed2004

Production of antimicrobial substances by lactic acid bacteria I: determination of hydrogen peroxide.

Restoration of the balance of different ecological niches has been proposed as a way to control the income of pathogenic microorganisms. The genus Lactobacillus has been used in different human and animal tracts as probiotic microorganisms with this objective in mind. The characteristics of the strains proposed as probiotics have been published or patented under the process of elaboration of different types of products. One of the mechanisms suggested to control the vaginal ecosystem is the production of antagonistic substances (lactic acid, bacteriocins, or H2O2). The H2O2-producing microorganisms present in the vagina of healthy women have been suggested as some of the bacteria responsible for maintenance of ecological balance, mainly in pregnant women. The absence of these microorganisms is related to a higher risk of: bacterial vaginosis, recurrent urinary tract infections by Escherichia coli, and acquisition of human immunodeficiency virus type 1 (HIV-1). Bauer has proposed that H2O2-producing lactobacilli also might exert control over vaginal cancer through specific interactions of reactive oxygen species, such as superoxide anion, hydroxyl radicals, and hypochlorous acid. The conversion of H2O2 into more toxic compounds during the oxidative process is potentiated by peroxidase and halures. This enzyme and some halures, such as chloride and bromide, are present in vaginal washes in sufficient amounts to allow an optimal environment for successful inhibition of pathogens. In vitro tests provide an approach for determining the ability of lactobacilli to produce H2O2. The H2O2 amounts produced in such systems are probably not a direct reflection of what happens in the vaginal tract of women or animals, which is not yet know. However, there is a registered patent with an H2O2-generating L. crispatus strain, also supporting the use of H2O2-producing lactobacilli to restore the vaginal ecosystem.

Anti-Infective Agents↗

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

Statistical models to optimize production of probiotic characteristics.

The use of probiotic microorganisms has been widely promoted in the last 20 years. Probiotics have applied to the gastrointestinal tract as capsules or as fermented milks. The characteristics of the strains proposed as probiotics have been published or patented after elaboration of the product. The first step in designing a probiotic product is to isolate and characterize strains with beneficial properties. Our group has reported the isolation and characterization of 134 strains of lactobacilli from the vagina of women from our city. Surface properties and the production of antagonistic substances has also been published. From these studies, certain strains were selected because they shared probiotic characteristics. The second step in the design of a pharmaceutical product is to determine the optimal conditions for obtaining the highest amount of viable microorganisms, as well as the best conditions to produce antagonistic substances. To perform these types of experiments, laboratory assays can be carried out to determine the optimum conditions in which the microorganisms can be cultured. Growth parameters and optimal growth conditions can be studied by the classical methodology or by the application of alternative methodologies. Alternative methods have been widely used in the food industry, including experimental designs to test multiple conditions at the same time, complemented by the use of statistical models to evaluate and compare all the conditions tested. The object of this chapter is to describe the experimental designs used to study the technological characteristics of vaginal probiotic lactobacilli as well as the application of statistical models for evaluation of the different conditions tested for the production of biomass and antagonistic substances in these bacteria. With this objective in mind, in the present chapter, the following areas are explored: 1. Growth experiments performed to study the effect of temperature, pH, agitation, and culture media on the growth and production of antagonistic substances by vaginal lactobacilli. 2. Fractional and complete factorial experimental designs used to perform the growth experiments. 3. Statistical models applied to evaluate the growth parameters and their modifications under the conditions assayed.

Bacteriological Techniques↗

PubMed2004

Colonization capability of lactobacilli and pathogens in the respiratory tract of mice: microbiological, cytological, structural, and ultrastructural studies.

Respiratory tract infections are among the bacterial infections that affect humans with higher frequency. Those produced by Streptococcus pneumoniae are reported to have the highest incidence in the world, affecting both children and old people. As a 2001 report from the World Health Organization expressed it, the basic fight of children under 5 yr old is to survive. Five different conditions (acute respiratory infections, diarrhea, measles, palludism, and undernutrition) directly produce more than 50% of the deaths in this age group. Respiratory tract infections in the developing countries in the Americas are among the first three causes of death in children under 1 yr and between the first and second cause in children between 1 and 4 yr old. Pneumonia is responsible for 85 and 90% of deaths in children under 5 yr old (approx 150,000 annually), 95% of them occurring in the developing countries in the Americas. There is an increased worldwide tendency to use preventive measures and to consume products that help to maintain the health status of the individual. Thus the use of probiotics has increased systematically during the last decade, and the scientific literature trying to demonstrate the positive effect of such preparations has also increased. The term probiotic has been applied to products that (1) contain live microorganisms, freeze-dried or included in fermented products or (2) improve the health status of humans and animals, exerting effects in the mouth or gastrointestinal tract (included in foods or capsules), in the respiratory tract (as aerosols), or in the urogenital tract (by local application)Having in mind the high incidence of respiratory tract infections, and looking for preventive measures as well as the possible applications of probiotics, the aim of this chapter was to use mice as experimental models to determine whether members of the genus Lactobacillus were able to colonize and give protection from infections after inoculation by the intranasal route. To this end, the following procedures were carried out: 1. Screening of the predominant bacterial species in respiratory organs. 2. Study of the kinetics of colonization of the different groups of microorganisms from 15 d up to adult (2 mo). 3. Screening of the probiotic characteristics of all the isolated strains.

Animals↗

PubMed2004

Effects of estrogen administration on the colonization capability of lactobacilli and Escherichia coli in the urinary tracts of mice.

The use of probiotic microorganisms has been widely promoted in the last 20 yr. They have been used in the gastrointestinal tract as capsules or as fermented milks. The characteristics of the strains proposed as probiotics have been published or patented under an elaboration process. The first step in designing a probiotic product is to isolate and characterize strains with some beneficial properties. The second step is to determine the optimal conditions to obtain the highest amount of viable microorganisms, together with the study of the best conditions to produce antagonistic substances. Urinary tract infections (UTIs) constitute a common cause of illness in pre- and postmenopausal women. It was estimated that 40-50% of adult women suffer a cystitis during their life. Ninety percent of acquired ambulatory UTIs and 30% of nosocomial infections are produced by Escherichia coli. The healthy human urinary tract is free of microorganisms, except for the anterior urethra, which is colonized by indigenous microbiota. The vaginal environment is a dynamic and complex ecological system with a highly heterogeneous microflora; thus favorable conditions exist for the colonization process, which is also affected by factors external to the tissues. The distal urethra and periurethral areas are separated ecological niches, both covered by the vaginal secretions that contain approx 109 microorganisms/mL. In these secretions, members of the genus Lactobacillus are predominant. Bacterial colonization does not increase because of the urinary flux, which clears the bacterial cells from the outer surfaces, as well as other factors such as pH, osmolarity, and urea concentration.

Animals↗

PubMed2004

Effect of lactobacilli administration in the vaginal tract of mice: evaluation of side effects and local immune response by local administration of selected strains.

Lactobacilli are the predominant microorganisms in the vaginal tract of human and some homeothermic animals. They can maintain the ecological equilibrium of the tract by protecting against pathogenic microorganisms. In the last few years, there has been an increased tendency to use probiotic microorganisms to restore the ecological equilibrium and to protect against infections. This principle has been widely applied to the gastrointestinal tract. More recently, some other studies have reported the application of probiotics in different tracts, for example, the urogenital or respiratory tract. One of the objectives of our group is to design probiotic products for the urogenital tract. With this purpose, lactobacilli were isolated from the human vagina, and later some of them were selected for their probiotic characteristics (production of antagonistic substances or adhesion capability). The application of probiotic products in the vaginal tract has been approached empirically; some pharmaceuticals containing these microorganisms are available in the United States or Europe or are protected under the patent process or intellectual property rights. There are not enough studies in humans or animals to determine whether their administration can produce some type of collateral or adverse effect. Using Balb/c mice as the experimental model, the object of the present work was to study (1) whether intravaginal administration of human lactobacilli can produce colonization of the tract; (2) whether such administration produces some type of adverse or collateral effect; and (3) whether probiotics are able to stimulate the local immune system. Keeping in mind that hormones can affect the colonization or persistence ability of microorganisms, and with the purpose of having all animals at the same point in the sexual cycle, animals were cycled with estradiol 48 h before inoculation with lactobacilli. They were then inoculated im with hormones 48 h before beginning microorganism inoculations. Later they were intravaginally inoculated with the appropriate dose of each Lactobacillus strains. The animals were sacrificed on different days after inoculation to perform the following studies: 1. Microbiological assays: To determine the number of lactobacilli in the tract (in vaginal washes or in organ homogenates), by plating the samples in selective media containing antibiotic (to differentiate the resident flora from those administered experimentally).

Animals↗

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↗

PubMed2004

Hydroxylapatite beads as an experimental model to study the adhesion of lactic acid bacteria from the oral cavity to hard tissues.

The oral environment contains many different types of microorganisms, including both Gram-negative and Gram-positive cocci, bacilli, and spirochetes. From the ecological point of view, the oral cavity is a perfect niche for certain bacteria such as lactobacilli because they interact, forming different types of communities. Lactobacilli have been associated with the generation of caries in some reports, secondary to the cariogenic Streptococcus. In previous papers, the isolation and identification of 145 strains from healthy subjects and from subjects with active caries were performed. Strains were characterized by their surface properties and also by the production of inhibitory substances. From all the strains, one isolated from the teeth of healthy patients and another from a patient with caries, sharing some surface properties, were selected for further study of their adhesion properties in an experimental model by using hydroxylapatite beads. Adhesion is the first step in the association of microorganisms with surfaces or mucous membranes. The first approach is a nonspecific interaction of both surfaces; later some other types of interactions can occur, involving more specific mediators of adhesions. Many different assays are available to study the adhesion phenomenon; some of them use predictive characteristics, and others use experimental models resembling the in vivo situation. Two model systems predominate. The most widely used has been saliva-coated hydroxylapatite or hydroxylapatite coated with buffers, proteins, and other substances. In an attempt to increase knowledge of the mechanisms of adhesion of oral lactobacilli with hard surfaces, this chapter describes an experimental model for studing the adhesion between lactobacilli and hard tissues represented by hydroxylapatite, the component most abundant in the teeth. The following steps were performed: 1. Obtaining the microorganisms. 2. Preparation of the hydroxylapatite beads. 3. Adhesion assay.

Dental Caries↗

PubMed2003

Comparison of the growth and hydrogen peroxide production by vaginal probiotic lactobacilli under different culture conditions.

OBJECTIVE: The purpose of this study was to determine the optimal conditions for the growth and hydrogen peroxide production by vaginal lactobacilli. STUDY DESIGN: Two vaginal lactobacillus strains were cultured under different growth conditions (temperature, pH, agitation, and growth media) with a fractional factorial experimental design. RESULTS: The optimal growth conditions of Lactobacillus paracasei CRL (Centro de Referencia para Lactobacilus Culture Collection) 1289 and Lactobacillus crispatus CRL 1266 were temperature 37 degrees C and initial pH 6.5, nonagitated cultures, in autolysat de levure; peptone, tryptone, Tween 80 et glucose (LAPTg) broth for L paracasei or in de Man-Rogosa-Sharpe (MRS) and LAPTg broths for L crispatus. The hydrogen peroxide production, detected only in agitated cultures, was higher at 37 degrees C and pH 6.5. The oxidative metabolite produced the self-inhibition of the lactobacilli growth. In mixed cultures of lactobacilli and Staphylococcus aureus under the optimal conditions of hydrogen peroxide production, the pathogen growth was inhibited. CONCLUSION: The results provided information about the factors that affect the hydrogen peroxide production and about the most favorable conditions with which to obtain the highest biomass in the shortest possible time.

Catalase↗

PubMed2002

Effect of the herbicide 2,4-dichlorophenoxyacetic acid on uropathogenic Escherichia coli virulence factors.

The effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D)-widely used in the world and mainly excreted by the renal route in exposed humans-were studied on the virulence and surface characteristics of an uropathogenic Escherichia coli strain. When the urine was supplemented with 2,4-D in vitro, the compound significantly reduced the bacterial fimbriation assayed by hemagglutination and surface protein quantification. Protein values decreased from 0.24 mg/g dw to 0.05 or 0.12 mg/g dw by 1 or 0.1 mM 2,4-D treatment, respectively. The effects in vivo were studied in groups of mice challenged intra-urethra with E. coli and exposed by the oral route with three different 2,4-D doses (2.6, 25 or 70 mg/kg bw) during 22 days. Depending on the dose used, the herbicide significantly decreased or removed bacterial cells in mice bladder and kidneys; except in the group treated with the highest dose from the 9th day of treatment. The histological studies showed mononuclear cell infiltration at low doses, and toxic damage in the renal parenchyma at prolonged exposure with higher doses, up to tisular necrosis in the 70 mg/kg bw group after 9 days of treatment. Our investigations performed in an experimental model suggest that short time 2,4-D exposure at low doses could act in prevention of UTI stimulating leukocytic migration and decreasing bacterial fimbriation. On the contrary, high doses and long-term exposure enhanced renal damage resulting in infection recurrence.

2,4-Dichlorophenoxyacetic Acid↗

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↗

PubMed2002

Estimation of vaginal probiotic lactobacilli growth parameters with the application of the Gompertz model.

Lactobacilli are widely described as probiotic microorganisms used to restore the ecological balance of different animal or human tracts. For their use as probiotics, bacteria must show certain characteristics or properties related to the ability of adherence to mucosae or epithelia or show inhibition against pathogenic microorganisms. It is of primary interest to obtain the highest biomass and viability of the selected microorganisms. In this report, the growth of seven vaginal lactobacilli strains in four different growth media and at several inoculum percentages was compared, and the values of growth parameters (lag phase time, maximum growth rate, maximum optical density) were obtained by applying the Gompertz model to the experimental data. The application and estimation of this model is discussed, and the evaluation of the growth parameters is analyzed to compare the growth conditions of lactobacilli. Thus, these results in lab experiments provide a basis for testing different culture conditions to determine the best conditions in which to grow the probiotic lactobacilli for technological applications.

Bacteriological Techniques↗