Effects of certain disinfectants and antibiotics on biofilm formation by Staphylococcus aureus isolated from medical devices at the University Hospital Center of Sidi Bel Abbes, Algeria

Background: Staphylococcus aureus is one of the species of bacteria most frequently isolated from medical devices. The ability to produce biofilm is an important step in the pathogenesis of these staphylococci infection, and biofilm formation is strongly dependent on environmental conditions as well as antibiotics and disinfectants used in the treatment and prevention of infections.Methodology: In this study, 28 S. aureus isolated from medical devices at the University Hospital Center of Sidi Bel Abbes in Northwestern Algeria were tested for biofilm formation by culture on Red Congo Agar (RCA). The tube method (TM) and tissue culture plate (TCP) techniques were also used to investigate the effect of penicillin, ethanol and betadine on pre-formed biofilm.Results: Nineteen S. aureus isolates produced biofilm on the RCA and 7 produced biofilms by the tube method, 2 of which were high producer. In addition, 9 S. aureus isolates produced biofilm on polystyrene micro-plates, and in the presence of penicillin and ethanol, this number increased to 19 and 11 biofilm producing S. aureus isolates respectively. On the other hand, no biofilm was formed in the presence of betadine.Conclusion: It is important to test for biofilm formation following an imposed external constraint such as disinfectants and antibiotics in order to develop new strategies to combat bacterial biofilms but also to better control their formation. Keywords : Staphylococcus aureus, biofilm, medical device, disinfectant, antibiotic French Title: Effets de certains désinfectants et antibiotiques sur la formation de biofilms par Staphylococcus aureus isolé à partir de dispositifs médicaux au Centre Hospitalier Universitaire de Sidi Bel Abbès, Algérie Contexte: Staphylococcus aureus est l'une des espèces de bactéries les plus fréquemment isolées des dispositifs médicaux. La capacité de produire du biofilm est une étape importante dans la pathogenèse de ces infections à staphylocoques, et la formation de biofilm dépend fortement des conditions environnementales ainsi que des antibiotiques et des désinfectants utilisés dans le traitement et la prévention des infections. Méthodologie: Dans cette étude, 28 S. aureus isolés à partir de dispositifs médicaux au Centre hospitalier universitaire de Sidi Bel Abbès dans le nord-ouest de l'Algérie ont été testés pour la formation de biofilm par culture sur gélose rouge du Congo (RCA). La méthode des tubes (TM) et les techniques de plaques de culture tissulaire (TCP) ont également été utilisées pour étudier l'effet de la pénicilline, de l'éthanol et de la bétadine sur le biofilm préformé. Résultats: Dix-neuf isolats de S. aureus ont produit un biofilm sur le RCA et 7 ont produit des biofilms par la méthode des tubes, dont 2 étaient très productifs. De plus, 9 isolats de S. aureus ont produit du biofilm sur des microplaques en polystyrène, et en présence de pénicilline et d'éthanol, ce nombre est passé à 19 et 11 isolats de S. aureus producteurs de biofilm respectivement. En revanche, aucun biofilm ne s'est formé en présence de bétadine. Conclusion: Il est important de tester la formation de biofilm suite à une contrainte externe imposée comme les désinfectants et les antibiotiques afin de développer de nouvelles stratégies pour lutter contre les biofilms bactériens mais aussi pour mieux contrôler leur formation. Mots-clés: Staphylococcus aureus, biofilm, dispositif médical, désinfectant, antibiotique &nbsp

Comparative Study of the Adsorption of Methyl Orange by Bentonite and Activated Carbon

The adsorption of methyl orange dye on activated carbon and bentonite type Algerian clay from aqueous solutions was investigated. The bentonite has been acid-activated, whereas the activated carbon was used without pretreatment. The influence of several parameters (kinetics, contact time, sorbent amount, adsorbate concentration and pH) on the adsorption capacity was evaluated and discussed. The methyl orange dye adsorption equilibrium of active carbon is lower than that of bentonite (3 h/1 h), whereas adsorption yield with active carbon is better than that of bentonite. The adsorption capacity of bentonite is lower than that of active carbon. The methyl orange dye adsorption increases with its concentration in the aqueous solutions. The Frendlich and Langmuir models provided the best fit to the experimental data with high correlation coefficient only for active carbon. The kinetic study demonstrated that methyl orange dye adsorption on bentonite was in a good accordance with the pseudo-second- order kinetic model. The results showed that bentonite-type clay gave acceptable results compared with activated carbon and is potential to be used as an economical adsorbent for the removal of methyl orange dye

The Role of CeO₂-Doping of γ-Al₂O₃ on its Structural and Superficial Area

A series of samples, noted Al_xCe_{1-x} has been prepared by hydrolysis, from γ-Al₂O₃ and CeO₂. These samples were calcined under air at 450, 900 and 1200°C, and then characterized by specific surface area, X-ray diffraction and thermoreduction programmed under H₂. Obtained results show that after calcination at 450 and 900°C, the cerium decreases the surface of alumina. Results of X-ray diffraction and thermoreduction programmed under H₂ experiments showed that the samples are constituted of: γ-Al₂O₃ and CeO₂. The global consumption of hydrogen increase with rate of CeO₂ added. At 1200°C, the sintering of the samples is very important and γ-Al₂O₃ is transformed into the α-phase. The decrease in specific surface area is more accentuated for Al₁Ce₀ sample, since sintering occurs due to the growth in crystallite size. Thermoreduction programmed under H₂ experiments show that reduction of CeO₂ much more accentuated for ceria samples or its decrease can reflect some alterations of the nature of interactions between Al₂O₃ and CeO₂

Study of effect of chromium on titanium dioxide phase transformation

International audienceMTiX samples with different atomic chromium percentages were synthesized by sol gel method and calcined at 400 degrees C under air. The effects of Cr and temperature on titanium dioxide phase transition were studied. In situ measurement showed the presence of anatase phase for all samples at temperature <500 degrees C. Without Cr content, the anatase rutile transition takes place at 600 degrees C and the rutile fraction increases with increase of temperature. In the presence of Cr content, rutile phase appeared at 700 degrees C. Cr2O3 phase was shown only in the case of CrTi20 content at 800 degrees C which indicates that the segregation remains modest. We have also studied the anatase rutile transition kinetics by using in situ X-ray measurements. It was found that the anatase phase stability increases as the chromium content increases. Results confirm that the transformation of anatase rutile is of first order

Preparation and characterization of MTiX for the catalytic oxidation of cyclohexane

International audienceMTiX (M = Cr and V) samples, with 0, 5, 10 and 20 atomic percent, were synthesised by a sol-gel method and calcined at 400 degrees C in air. The XRD analysis results indicated that the materials presented a crystalline structure with the presence of TiO2 anatase forms. BET analysis showed that the surface area varied with the variation of metal content. EDX analysis showed a heterogeneous distribution of samples. The results of pyridine adsorption followed by FT-IR indicated that Bronsted and Lewis acid sites are present on the surface of catalysts. Liquid phase oxidation of cyclohexane was carried out under milder reaction conditions over MTiX catalysts using tert-butyl hydroperoxide (TBHP) as oxidant, acetic acid and acetonitrile as solvents. The results indicated that conversion depends on metal content and solvent polarity. Chromium is selective for cyclohexanol. The best result was obtained with VTi20 with 35% of conversion and 92% of olone selectivity

Structural and textural modifications of ZrO2 induced by La2O3 addition, thermal treatment and reducing process

International audienceLanthana-doped zirconium oxide may strongly influence the solid state reaction. A series of samples denoted ZrxLa1–x (where x = atomic percentage of the element) are prepared by hydrolysis in the neutral medium from ZrO2 and La2O3. These samples are calcined under air at 450, 900, and 1200 °C, then characterized by specific surface area (BET), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermoreductions programmed under H2 (TPR—H2). The results show that after calcination at 450 °C, the lanthanum addition increases slightly the zirconia surface area and the XRD analysis does not reveal any interaction between two oxides. After calcination at 900 °C, sintering appears and oxides lose half of their surface area. Lanthanum is not inserted into the structure of ZrO2, while some interaction occurs between lanthanum and zirconium oxide. At 1200 °C, the sintering of the samples is very important; the specific surface is about 1 m2/g; XRD results show that ZrxLa1–x are formed basically by three mixed oxides: La2Zr2O7, La0.5Zr0.5O1.75, La0.46Zr0.54O1.77, which is confirmed by the SEM method. H2-TPR experiments confirm that changes in the reducibility can reflect some alterations of the nature of interactions between ZrO2 and La2O3. Preliminary experiments on zirconia do not reveal the occurrence of significant reduction processes. On the other hand, extensive reduction of La2O3 is much more accentuated for lanthana samples. At high temperatures, a significant lessening in the H2 consumption suggests that ZrO2 would likely interact with La2O3, which is confirmed in the results indicating the presence of the pyrochlore type of oxides mentioned above