Biomedical subjects

J Liébana

Publications and source records attributed to J Liébana.

At least 19 recordsLinked to original sources

PubMed2001

Comparative study of the influence of melatonin and vitamin E on the surface characteristics of Escherichia coli.

AIMS: Melatonin is a hormone produced by the pineal gland and that affects the response of various cell membranes to an oxidative stimulus. METHODS AND RESULTS: The present study evaluates the hydrophobic characteristics of Escherichia coli in response to melatonin (100 nmol l(-1), 200 micromol l(-1)) and to vitamin E (5 mg dl(-1)). A reduction was found in the surface hydrophobicity of E. coli at concentrations of 200 micromol l(-1) melatonin in a Müeller-Hinton (MH) broth. These effects were modified when a protein synthesis inhibitor (chloramphenicol) was added at sub-lethal concentrations to the broth. Vitamin E produced a greater diminution in surface hydrophobicity than melatonin. The adherence of E. coli to nitrocellulose filters increased in the presence of melatonin + chloramphenicol, and vitamin E. The effects observed were independent of the concentration of iron in the broth. CONCLUSION: Oxidative stress plays an important role in modifying the surface characteristics of E. coli, which could affect the micro-organism's capacity to adhere to epithelia. SIGNIFICANCE AND IMPACT OF THE STUDY: We think that the oxide reduction potential of the host may be a determinant factor in the bacterial colonization of animal tissue.

Animals↗

PubMed2001

In vitro antibacterial activity of glass-ionomer cements.

The in vitro antibacterial activity of the glass-ionomer restorative cements Ketac-Cem, Ketac-Bond, Ketac-Silver and Vitrebond was studied in conjunction with 32 strains of five bacteria involved in the development of caries: Streptococcus spp., Lactobacillus spp., Actinomyces spp., Porphyromonas spp. and Clostridium spp. The agar plate diffusion method was used for the cultures, which included a chlorhexidine positive control. All the glass-ionomer cements tested inhibited bacterial growth, but with considerable differences in the scope of their action. Of the four cements, Vitrebond, a resin-modified glass-ionomer cement, was determined to be the most effective bacterial inhibitor.

Anti-Bacterial Agents↗

PubMed2000

[Analysis using ELISA test of antibody response to Fusobacterium nucleatum and Eikenella corrodens in subjects with periodontal disease].

BACKGROUND: To know the synthesis of IgG, IgA, and IgM to Fusobacterium nucleatum and Eikenella corrodens in serum, crevicular liquid and saliva in subjects with periodontal disease, using ELISA test. PATIENTS AND METHODS: We studied 26 patients with high bias to the disease aged less than 35 years and 30 individuals with comparable age and with scarce bias to the disease. RESULTS: No differences were found for IgG and IgM titers between the groups, except for IgM to E. corrodens. For IgA, differences were found when the saliva and crevicular liquid were studied for both bacteria, as occurred in serum IgA compared to E. corrodens. In all the cases antibody levels were lower in the patients. CONCLUSIONS: The lower synthesis of IgM and IgA, fundamentally the latter, to F. nucleatum and E. corrodens in patients with periodontal disease would contribute to the pathogenesis of this illness.

Adult↗

PubMed2000

Post-pH effect in oral streptococci.

OBJECTIVES: To study the post-pH effect (PpHE) in 11 strains of oral streptococci belonging to Streptococcus sanguis, S. mitis, S. gordonii, S. mutans and S. sobrinus by using the BacT/Alert microbial detection system. METHODS: The bacterial cultures were exposed to a different pH (3.6, 4.0, 4.6, 5.0, 5.6, 7.0, 7.5, 8.0 and 8.6) for 1 h, and then returned to a neutral medium. The automated BacT/Alert system determined resumed microbial growth by measuring CO2 generation. The PpHE expresses the time difference between resumed growth (after pH shock) and optimal growth (pH 7.0 used as the control). RESULTS: PpHE was found to be minimal for alkaline pH values, and to be strain and species dependent. CONCLUSIONS: The PpHE may be useful as an ecological determinant or as an indicator of the cariogenicity of oral streptococci.

Carbon Dioxide↗

PubMed2000

The influence of different concentrations of melatonin on the cell surface hydrophobic characteristics of Neisseria meningitidis.

The cell surface hydrophobicity of micro-organisms is a characteristic that has been associated with the colonization of mammalian epithelia and with their capacity to induce diseases. Melatonin is a hormone produced by the pineal gland that affects the immune response mechanism. This study investigated, as an expression of the virulence of Neisseria meningitidis, how its hydrophobic characteristics were affected by exposure to increasing concentrations of melatonin. An increase in the cell surface hydrophobicity of N. meningitidis was found at concentrations of 1 mmol l(-1), while lower concentrations of melatonin did not significantly affect this particular cell surface characteristic of the micro-organism. It may be concluded that melatonin clearly influences the cell surface hydrophobicity of N. meningitidis, a circumstance that should be taken into account in future studies to determine whether this hormone plays a role in the variable pathogenicity of the bacteria in different hosts.

Bacterial Adhesion↗

PubMed1997

In-vitro susceptibility, tolerance and glycocalyx production in Streptococcus mutans.

We studied the presence of high-level resistance to aminoglycosides, penicillin tolerance and glycocalyx production in 160 isolates of Streptococcus mutans. Susceptibility to amoxycillin, cefazolin, imipenem, erythromycin, clindamycin, vancomycin and teicoplanin was also investigated. Of the isolates analysed, 58.8% produced glycocalyx in vitro and 2.5% were penicillin-tolerant. High-level resistance to streptomycin was found in 16.3% of the isolates, but all were sensitive to all other antibiotics tested. We found no significant relationship between glycocalyx production and high-level streptomycin resistance, penicillin tolerance or antibiotic susceptibility, except for a greater susceptibility to clindamycin and vancomycin in isolates that produced glycocalyx. Although our findings reflect the clinically favourable pattern of susceptibility currently found in this species, the appearance in some isolates of resistance, tolerance and glycocalyx production should be investigated because of the risks involved in endocarditis caused by S. mutans.

Aminoglycosides↗

PubMed1996

Initial pH as a determining factor of glucose consumption and lactic and acetic acid production in oral streptococci.

Lactic and acetic acid production was evaluated from six strains of oral streptococci, viz Streptococcus gordonii, Streptococcus mutans, Streptococcus oralis, Streptococcus salivarius, Streptococcus sanguis and Streptococcus sobrinus cultured in the presence of 1, 5, 10 mM glucose and without glucose, at initial pH values of 5, 5.5, 6 and 7. S. sobrinus and S. salivarius caused the greatest decreases in pH. At pH values of 5 and 5.5, lactic acid and acetic acid production in the species tested was discordant with residual glucose levels. Acid production from protein was especially great in S. mutans and S. salivarius.

Acetic Acid↗

PubMed1995

Evaluation of the automicrobic system for the identification of Streptococcus mutans.

The performance of the Automicrobic System with the Vitek gram-positive identification card (bioMérieux, France) in identifying strains of Streptococcus mutans was studied. Of 160 strains assayed, 72.5% were confirmed to be Streptococcus mutans; the remainder were identified as other species of streptocci (Streptococcus bovis, Streptococcus uberis, Streptococcus anginosus, Streptococcus sanguis I and II, Streptococcus intermedius, and Streptococcus constellatus).

Bacterial Typing Techniques↗

PubMed1995

Environmental microbial contamination. Pilot study in a dental surgery.

Environmental contamination by bacterial aerosols occurs every day in the dental surgery. The aim of this study was to determine bacterial levels in five different areas of a dental surgery during ultrasonic scaling procedures using bacterial cultures. Two areas with markedly different amounts of infective aerosols were identified. The role of the air conditioning system was also assessed. There was evidence that the air conditioning system could act as a vehicle for the transmission of microorganisms.

Aerosols↗

PubMed1994

Action of sodium fluoride on phagocytosis by systemic polymorphonuclear leucocytes.

Alterations in phagocytosis appear to be important in the onset and development of periodontitis. We investigated new substances that may be of use in the treatment of periodontitis. In a preliminary study, we tested the effect of sodium fluoride on phagocytosis by circulating polymorphonuclear leucocytes (PMNs) in 10 replicate assays using blood from six healthy subjects. Sodium fluoride was tested at concentrations of 1.0 micron to 4.0 microns against Streptococcus oralis, Streptococcus mutans, Streptococcus sobrinus and Streptococcus sanguis. The phagocytic index against all microorganisms increased significantly at all concentrations of sodium fluoride assayed; this effect was dose dependent. Sodium fluoride appeared to stimulate phagocytosis via two mechanisms: an apparent increase in bacterial susceptibility to phagocytosis, and direct stimulation of phagocytosis by PMNs.

Adult↗

PubMed1994

Physiopathology of primary periodontitis associated with plaque. Microbial and host factors. A review. Part 1.

Microbial factors involved in the genesis of periodontitis include colonization, bacterial penetration of the epithelium, multiplication and invasive-destructive capacity. Colonization of the gingival sulcus is related, to a certain extent, to supragingival plaque. Bacterial multiplication is induced by nutrients in the gingival fluid, and nutrients produced by degradative and excretory microbial activity. Invasion and destruction are mediated by exotoxins, structural elements of the bacteria, enzymes, metabolites, polyclonal lymphocyte activity, fibroblastic cytotoxicity, and leukocyte chemotactic inhibition.

Bacteria↗

PubMed1994

Physiopathology of primary periodontitis associated with plaque. Microbial and host factors. A review. Part 2.

To a considerable extent, host factors condition the initiation and progression of periodontitis. The integrity of the periodontal structures and the immune elements in the gingival fluid may act as a defensive barrier against microorganisms. However, immune over-response may lead to tissue damage and bone resorption from anaphylactic reactions, immunocomplex reactions, type IV hypersensitivity, complement hyperactivation via the alternative pathway, or direct action of leukocytes and macrophages. Moreover, insufficient host response allows bacteria to escape control, allowing more rapid progression of the disease.

Bacteria↗

PubMed1993

Evaluation of the capacity of oral streptococci to produce hydrogen peroxide.

The capacity of 11 strains of oral streptococcal species (Streptococcus sanguis, S. oralis, S. mitis and S. sobrinus) to produce hydrogen peroxide (H2O2) was studied in vitro. Detection of this property in solid media, particularly with trypticase soy agar-benzidine-peroxidase, was more sensitive than in liquid media. The addition of carbohydrates (arabinose, xylose, mannose, sorbose and lactose), sorbitol and saccharine to buffered trypticase soy broth increased H2O2 production in S. oralis NCTC 11427, although the concentrations obtained with some substrates (glucose, galactose, mannitol and xylitol) were lower than those obtained in controls. In S. sanguis NCTC 7863, H2O2 production was detected only with galactose, sorbitol, lactose and saccharin.

Carbohydrate Metabolism↗

PubMed1993

Immunological methods for the detection of structural components and metabolites of bacteria and fungi in blood.

This review compares the clinical usefulness of immunological methods for the detection of structural components and metabolites of bacteria and fungi. Bacterial antigens (especially those of Mycobacterium, Neisseria, Staphylococcus aureus, Yersinia enterocolitica, Escherichia coli, Salmonella, Chlamydia, and Brucella) are best detected by enzyme-linked immunosorbent assay. Methods involving antibodies are more expensive and are effective only when performed in series. The detection of antibodies that recognize S aureus teichoic acid merely confirms the presence of a metastatic complication. Tissue invasion by Candida albicans is not yet reliably detectable by the presence of a specific antigen. Simple, but not completely reliable methods are available such as the latex test for mannans detection and/or agglutination with liposomes for detecting 48-kDa cytoplasmic protein antigen and an assay for detecting enolase antigen. A latex agglutination test has also been developed for the mannans antigen of Aspergillus and for Cryptococcus neoformans capsular polysaccharide; the latter test is more cost effective. The sensitivity of both tests is improved by serial assays. A negative finding with hemagglutination-based antibody tests rules out C albicans infection, and titers of 1/640 or higher have been associated with disseminated infection by Aspergillus. Concentrations of C albicans blastopore antigen antibodies higher than 400 IU/ml can be seen in disseminated candidiasis. High concentrations of endotoxin are indicative of imminent septic shock. Some biological indicators (C reactive protein, angiotensin converting enzyme, fibronectin, elastase-alpha 1-antitrypsin complex, tumor necrosis factor and interleukin-6) have been used to rule out a bacterial cause of fever.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Bacterial↗

PubMed1993

Phenotypic characterization of oral streptococci by classical methods.

The phenotypic characteristics of 215 strains of oral streptococci were compared on the basis of the results of sorbitol, raffinose and trehalose fermentation, ammonium from arginine production, aesculin hydrolysis, H2O2 production, susceptibility to 2 U bacitracin, and growth in 4% NaCl solution. Eleven different species were identified. Among the most noteworthy findings were the low number of H2O2-producing strains of Streptococcus sobrinus, the effective discrimination between Streptococcus sanguis and Streptococcus mitis on the basis of raffinose fermentation, and the phenotypic similarity between Streptococcus oralis and the former mutans group. To avoid the creation of new species, the term biotype is proposed to designate phenotypically distinct organisms which do not qualify as different species.

Dental Plaque↗

PubMed1992

In vitro immune modulation of polymorphonuclear leukocyte adhesiveness by sodium fluoride.

We investigated the influence of sodium fluoride on polymorphonuclear leukocyte (PMN) adhesiveness in a healthy subject with low serum levels of fluoride. The PMN were separated from venous blood, and the percentages of adhered and unadhered cells were determined in vitro in plastic culture plates. The cells were cultured with five different fluoride concentrations ranging from 6.25 10(-2) microM to 4.0 microM in the presence and absence of autologous serum. PMN adhesiveness in both the presence and in the absence of autologous serum was 98.5%; the addition of fluoride had no effect on the results in the absence of serum. However, in the presence of autologous serum, PMN adhesiveness decreased significantly with the addition of fluoride (P < 0.05) from 0.5 microM. The decrease was smaller (1.1%) at a concentration of 0.125 microM, and larger at 12 times this concentration of fluoride (52.7%). We conclude that sodium fluoride reduces PMN adhesiveness in a dose-dependent manner. The effect is not direct, but should be modulated by a seric factor.

Adult↗

PubMed1991

Phagocytosis and adhesiveness of peripheral blood polymorphonuclear leukocytes in patients with rapidly progressive periodontitis.

Phagocytosis and adhesiveness of peripheral blood polymorphonuclear leukocytes were studied in patients diagnosed with generalized rapidly progressive (form A) periodontitis. All patients belonged to a single family and were first degree relatives. In the patients' leukocytes there was a statistically significant reduction in phagocytic index and adhesiveness, in comparison with leukocytes from controls. However, adhesiveness approached control values in the presence of autologous serum, thus implying that serologic factors may enhance this function in patients with this type of periodontitis.

Adult↗

PubMed1991

Oral ecology and its pathogenic relation with the origin of primary periodontitis associated with plaque.

Microbial factors involved in the genesis of periodontitis are related with supragingival (coronal) and subgingival plaque. The microorganisms in the supragingival plaque reach the gingival sulcus, and are influenced by ecological determinants in this zone which condition the establishment of adherent plaque. This plaque may subsequently form the substrate for particularly periodon to pathogenic bacteria, which may then form plaques adhered to the epithelium, or develop as floating (nonadhered) populations. After microbial colonization of the gingival sulcus, bacteria or substances they produce may reach the junctional epithelium and alveolar bone, leading to direct tissular destruction to an extent determined by the host's immune response. Damage may be local or generalized, depending on additional factors.

Dental Plaque↗