Biomedical subjects

R M Domingues

Publications and source records attributed to R M Domingues.

12 recordsLinked to original sources

PubMed2001

Antimicrobial resistance of strains of the Bacteroides fragilis group isolated from the intestinal tract of children and adults in Brazil.

The results of this study show that there is a high frequency of resistant species in the Bacteroides fragilis group in the intestinal tract of children and adults in Brazil. B. fragilis was not studied. Of the 73 strains examined, B. distasonis was the most resistant species to penicillin, cefoxitin, cefotaxime and clindamycin. High rates of multiresistance were found, most commonly to penicillin and clindamycin (18 of 36 strains). High levels of beta-lactamase production were detected in isolates showing high resistance to penicillin and multiresistance to the cephamycins, suggesting a widespread dissemination of such resistance.

Adult↗

PubMed2000

Resistance profile of Bacteroides fragilis isolated in Brazil. Do they shelter the cfiA gene?

The epidemiology of antimicrobial resistance of clinical isolates and human intestinal strains of Bacteroides fragilis has assumed great importance in the last few years since this microorganism, like other members of the B. fragilis group, can be responsible for the spread of resistance determinants. It is possible that the presence of B. fragilis in polluted aquatic environments might contribute to the spread of resistance. The antimicrobial resistance profile of 44 clinical B. fragilis strains isolated from 1981-1988 and 1991-1998 from the University hospital of Rio de Janeiro, and of 17 faecal and 17 polluted aquatic environmental B. fragilis strains isolated between 1991 and 1998 was determined. The susceptibility tests against penicillin, cefoxitin, imipenem, meropenem, clindamycin, chloramphenicol and metronidazole were performed by Etest in Wilkins-Chalgren agar enriched with 5% sheep blood. Motivated by some high MIC values for cefoxitin and meropenem, the cfiA gene, which codes for a metallo-beta-lactamase, was investigated among all strains, using PCR amplification. The resistance to penicillin was high in the samples from 1981 to 1988 (92.9%) and also in those from 1991 to 1998 (100%), although the MIC90 decreased from 256 mg/L to 24 mg/L. An increase in the resistance level to clindamycin and cefoxitin was seen from one decade to the other, the MIC90 values changing from 4 mg/L to 12 mg/L and from 8 mg/L to 32 mg/L, respectively. The susceptibility profile for metronidazole, chloramphenicol, imipenem and meropenem remained stable, although two clinical strains showed MICs of 6 mg/L and 8 mg/L against meropenem. Almost all human intestinal strains were resistant to penicillin and all of them were susceptible to imipenem, meropenem, chloramphenicol and metronidazole. The MICs of meropenem against two strains isolated from a polluted aquatic environment were 6 mg/L and 32 mg/L. The cfiA gene was detected in five strains, two of which were isolated from clinical specimens against which the MIC values of cefoxitin were high and three from an aquatic environment, whose susceptibility to both cefoxitin and meropenem ranged from sensitive to resistant.

Bacterial Proteins↗

PubMed1999

Bacteroides fragilis isolates compared by AP-PCR.

Bacteroides fragilis is a component of the normal intestinal flora and an important pathogen in nonintestinal endogenous infections. It has been associated with enteric infections and has already been detected in polluted water. In order to evaluate the genetic diversity of B. fragilis, a total of 31 isolates and two reference strains were examined. This collection included strains from nonintestinal infections [12], intestinal infections [5], intestinal microflora [10], aquatic environments [4], and the reference strains ATCC 25285 and ATCC 23745. DNA fingerprints were detected using two separate PCR reactions with different arbitrary primers. The computer-assisted system Taxotron (Institut Pasteur, Dr P. Grimont) was used to analyze the profiles obtained and dendrograms were generated. By using a distance of 0.65 as the threshold, two clusters (hereafter referred to as genotypes I and II) were defined. Strains of differents origins could be distributed into both genotypes. We were unable to detect any obvious correlation between a given genotype and the specific disease or the source of the corresponding strains.

Bacteroides fragilis↗

PubMed1999

Production of bacteriocin by Bacteriodes fragilis and partial characterization.

The ability of Bacteroides fragilis strains, isolated from various sources, to produce bacteriocin was evaluated. All strains isolated from intestinal infections were producers in high levels and less susceptible to the others. Strains from other origins were found to produce bacteriocin at a medium level and they were variably susceptible. Some properties of one bacteriocin produced by the Bact. fragilis 079298-3 strain were analysed, providing evidence of its protein nature, with stability over a wide range of pH and retained inhibitory activity after heating. This variability seems to suggest that bacteriocin typing is a good method for this species.

Animals↗

PubMed1998

Electrophoretic characterization of exposed outer membrane proteins in environmental and human Bacteroides fragilis strains.

Bacteriodes fragilis isolated from aquatic environment, from infectious process and from human feces were compared as to their outer membrane protein electrophoretic profiles after staining with Coomassie blue and reacting with antibodies prepared against whole-cell antigens of a reference strain from a clinical source. A marked homogeneity was found among the strains with these methodologies. The profiles of all strains obtained after radio-iodination of the intact cell showed qualitative similarity when compared with the profiles obtained by the other methods. Thus, these data allow us to suggest the designation of the peptides observed in the autoradiograms as surface-exposed proteins. Differences observed in the autoradiograms in the expression of bands mainly detected at a molecular weight of 28 in the commensal strain 118,310 defined previously as avirulent, in addition to a distinction in the titres of agglutination with the sera tested and lower reactivity in the immunoblotting assays, suggest a relationship of the B. fragilis surface architecture with the virulence potential as well as with the origin of the strain.

Agglutination Tests↗

PubMed1998

Influence of stress conditions on Bacteroides fragilis survival and protein profiles.

Bacteroides fragilis strains isolated from different sources, i.e. 1 strain (AA1) from an aquatic environment, 1 strain from normal flora (118310) and the type strain (ATCC 25285) originally isolated from clinical material, were analysed for both cell envelope proteins composition and surviving under oxidative stress starvation. All strains examined showed a similar survival response when cultured in drinking water with a ten-fold decrease in viable counts per day during the 7 days of analysis. The outer membrane protein (OMP) profiles of all strains were quite similar during the stress period as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). However, the periplasmic proteins of the strain 118310 showed two protein bands at 48 and 58 kDa, respectively, that were absent in the strains AA1 and ATCC 25285 during the incubation period in potable water. Whole cells and periplasmic 35S-labelled proteins from bacteria cultured in drinking water showed a significant increase in proteins at 16, 18, 24, 26, 35, 48, and 58 kDa and 18, 22, 24, 48, 58, and 70 kDa, respectively, in all strains when compared to cells grown in BHI-PRAS media as detected by autoradiography following SDS-PAGE. These data suggest that B. fragilis may have a synthesis mechanism that allows them to adapt to adverse environments.

Bacterial Outer Membrane Proteins↗

PubMed1997

Whole-cell and periplasmic protein banding patterns of environmental and human Bacteroides fragilis strains.

In order to investigate the relationship among virulent and avirulent Bacteroides fragilis strains, SDS-PAGE of whole-cell proteins (WP) and periplasmic proteins (PP) were used to establish a protein profile of strains isolated from human infections, fecal flora and environmental water. Despite different sources of the strains, no significant differences were observed as determined by the WP SDS-PAGE analysis. In contrast, the proteins obtained from the bacterial periplasm showed differences in the electrophoretic protein profile. Two distinct PP profile patterns were obtained. Pattern A included 6 out of the 8 virulent strains and pattern B, 6 out of 8 avirulent strains. Interestingly, an environmental strain that was capable of inducing abscesses in mice, had a PP profile highly similar to that of the virulent strains from human infections. These data indicate that PP from B. fragilis may be useful to characterize differences among virulent and avirulent strains. Moreover, strains isolated from environmental water may also be a source of exogenous infections by B. fragilis.

Animals↗

PubMed1997

Surface vesicles: a possible function in commensal relations of Bacteroides fragilis.

Surface vesicles (SV) defined by electron microscopy as outer membrane (OM) extrusions were detected in Bacteroides fragilis strains from distinct sources. A partial identity between SV and OM electrophoretic protein profiles, in addition to the microscopic analysis, may suggest the designation of OMSV. Sialidase activity, a virulence determinant, was associated with these sub-cellular structures in all the strains, but in an inverse relation to the vesicle quantity per cell. A commensal strain, previously defined as avirulent in an animal model, presented the lowest vesicle-associated sialidase activity and the greatest SV expression as opposed to what happened with clinical and environmental strains. These results seem to suggest that these surface components have a function in commensal stages of B. fragilis.

Bacterial Outer Membrane Proteins↗

PubMed1995

Bacteroides fragilis: an exogenous pathogen?

Thirteen strains of Bacteroides fragilis isolated from contaminated water or from cases of intestinal and non-intestinal infections were comparatively analyzed in order to detect a possible biological relationship among them. The observation of similar profiles among the two groups, regarding the capacity of inducing abscesses and some surface properties, may support the hypothesis that the species could also act as an exogenous pathogen.

Abscess↗

PubMed1992

Sialic acid as receptor of Bacteroides fragilis lectin-like adhesin.

It was observed that sialic acid and macromolecules rich in this sugar were able to inhibit the hemagglutination activity (HA) of Bacteroides fragilis strains in low concentrations. Reversion of the HA and also of the adsorption to beads of Sepharose coupled to bovine submaxillary mucin, by this sugar residue corroborated the recognition capacity of the bacterial lectin-like adhesin. However, when erythrocytes were treated with clostridial neuraminidase, an increase in the HA of some strains was observed. Protease treatment of erythrocytes abolished the HA, indicating that cell receptors of B. fragilis are probably a glycoprotein moiety.

Adhesins, Bacterial↗

PubMed1991

Effect of metronidazole on surface properties of Bacteroides fragilis.

The effects of subinhibitory concentrations of metronidazole on the general morphology, ultrastructure and charge and hydrophobicity of Bacteroides fragilis were investigated using transmission and scanning electron microscopy, and measurements of zeta-potentials and contact angles. Metronidazole treatment induced morphological alterations in B. fragilis. Cells became filamentous and showed a significant loss of cytoplasm. The surface anionogenicity and hydrophobicity of B. fragilis were enhanced by the drug treatment. Metronidazole, by modifying B. fragilis surface properties, could alter, indirectly, interactions with host cells.

Bacteroides fragilis↗

PubMed1989

Influence of metronidazole, chloramphenicol, clindamycin and penicillin G on growth and neuraminidase activity of Bacteroides fragilis.

The effects of subinhibitory concentrations of metronidazole, chloramphenicol, clindamycin and penicillin G on cell growth and neuraminidase activity of Bacteroides fragilis were tested in six strains from clinical specimens and two type collection strains. All showed significant inhibition of cell growth at one half the MIC after 24 h incubation. Metronidazole at one quarter the MIC was significantly inhibitory after 24 and 48 h incubation. The neuraminidase activity remained unaltered, in comparison with controls, when metronidazole and clindamycin were tested. Chloramphenicol reduced the enzyme activity at both one half and one quarter the MIC. On the other hand, penicillin G enhanced the neuraminidase activity, although the difference was not statistically significant. These in-vitro effects may simulate the behaviour of the bacteria in abscesses in vivo.

Bacteroides fragilis↗