Biomedical subjects

J Azeredo

Publications and source records attributed to J Azeredo.

5 recordsLinked to original sources

PubMed2006

Candida albicans and Candida dubliniensis: comparison of biofilm formation in terms of biomass and activity.

Candida albicans and C. dubliniensis are two species responsible for oral candidiasis, especially in immunocompromised patients. Microbial infection is preceded by adherence and biofilm formation. Biofilm formation represents the most common form of C. albicans in the oral cavity and is considered to be one of the most important virulence factors. In this study, the biofilm formation ability of C. dubliniensis was compared with that of C. albicans in terms of biomass (quantified using crystal violet) and activity (assessed by formazan salts formation). Both species formed heterogeneous biofilms; however, species and strain variations were seen in the quantification of biomass and activity. There was no correlation between pseudohyphae formation and biofilm formation capability.

Biofilms↗

PubMed2006

Staphylococcus epidermidis adhesion on modified urea/urethane elastomers.

Block urea/urethane co-polymer films present elastomeric properties with the possible tuning of their surface properties within a wide range and are therefore considered relevant surfaces for possible medical applications. In particular, thin free standing films of urea/urethane elastomers with two soft segments, polypropylene oxide and more hydrophobic polybutadiene, develop multistable states with surface topography features with remarkable regularity. Moreover, complex surface structures may be obtained by UV radiation treatment followed by suitable mechanical action and also by extraction of the elastomer with a suitable solvent. In the present work, different modified elastomer samples were assayed for Staphylococcus epidermidis adhesion during 2 h and the extent of bacterial adhesion was evaluated by automatic cell enumeration. Bacterial adhesion assays demonstrate that the typical trend relating the increase in the number of adhered bacteria with the increase of the surface roughness does not hold for all materials. Results may be interpreted taking into account both the surface topography and the different types of micro-phase segregation of hydrophobic and hydrophilic parts of the elastomer.

Bacterial Adhesion↗

PubMed2005

Influence of sub-inhibitory concentrations of antimicrobial agents on biofilm formation in indwelling medical devices.

Biofilms of Staphylococcus epidermidis and Candida spp. are two of the most frequent factors of infections associated with the use of indwelling medical devices. Several strategies have been proposed and/or developed to prevent infection. The aim of this study was to compare the effect of sub-inhibitory concentrations of anti-microbial agents on biofilm formation. Biofilms of three strains of S. epidermidis and two of both Candida albicans and Candida dubliniensis were formed in the presence of three antibiotics and two antifungal agents respectively. Based on the control samples, the percentage of biofilm formation inhibition by the different agents was determined and compared. The results showed that the influence of the antibacterial and antifungal agents tested is strain dependent, with the effect of the different agents also varying among strains, even though they have the same mechanism of action.

Amphotericin B↗

PubMed2004

Influence of batch or fed-batch growth on Staphylococcus epidermidis biofilm formation.

AIMS: To make a quantitative evaluation of the differences in biofilm formation by Staphylococcus epidermidis using batch and fed-batch growth systems and to correlate this with production of the major biofilm polysaccharide, poly-N-acetyl glucosamine (PNAG). METHODS AND RESULTS: Dry weight measurements of biofilms formed in batch and fed-batch conditions were compared with haemagglutination titres, which measure the amount of PNAG produced. Strains grown in batch systems developed less biofilm than when grown in fed-batch systems. A good correlation was found between the amount of biofilm formed in fed-batch systems and the haemagglutination titres. CONCLUSIONS: Differences in biofilm formation and PNAG production by S. epidermidis are dependent on the availability of nutrients, with higher availability correlating with more biofilm and PNAG production. SIGNIFICANCE OF AND IMPACT OF THE STUDY: Comparisons of the formation of biofilms by S. epidermidis are dependent on choosing an appropriate biofilm growth system. Comparability or disparity of conclusions among different investigations will be strongly influenced by which mode S. epidermidis biofilms are formed.

Acetylglucosamine↗

PubMed2003

Extraction of exopolymers from biofilms: the protective effect of glutaraldehyde.

The extraction of the exopolymeric matrix is a prerequisite to properly assessing the composition of the biofilm. Several extraction methods have already been developed, however, no universal method has yet been adopted because the compromise between high yields of extraction and minimum cell lysis is difficult to establish. In fact, most of the extraction methods promote leakage of intracellular material. The most common extraction methods, Dowex resin and sonication, were assayed in biofilms of Pseudomonas fluorescens and Alcaligenes denitrificans submitted to a pre-treatment with glutaraldehyde (GTA). The assessment of ATP released after extraction was used as a criterion of cell lysis. The results showed that GTA is a protective agent against cell lysis. The pre-treatment with GTA is particularly useful combined with sonication.

Alcaligenes↗