Isolates of Klebsiella pneumoniae are responsible for opportunistic infections in humans, particularly of the urinary respiratory tracts. These bacteria express type 3 fimbriae that have been implicated in binding to eukaryotic cells and matrix proteins. Twenty four (24) K. pneumoniae strains isolated from medical devices were studied. Their capacity to form biofilm was assessed using two types of materials, polyvinylchloride (PVC) and glass of microfermenter in static or kinetic conditions. Strains with adherence to PVC also cling strongly to glass slides. We determined the in vitro effects of three antimicrobial agents against planktonic and biofilm forms of K. pneumoniae and we demonstrated that isolates of the biofilm form were at least 10-25 times more resistant than the planktonic form. Most strains of K. pneumoniae harbored the mrkD gene and exhibited a strong ability to adhere to inert surfaces.

Acinetobacter baumannii is an opportunistic pathogen responsible for nosocomial infections due to biofilm formation on the surface of implantable medical devices. Thirty (30) strains of A. baumannii were isolated from medical devices and tested for their ability to form a biofilm. The factors that may influence this process, such as the hydrophobicity of the bacterial wall, temperature, duration of implantation and the nature of the medical device, were also investigated. Strains were able to form a biofilm; however this process was more substantial at 30°C than at 37°C and was maximal after 96 h of incubation. Strains seem to adhere better to silicone and latex than to polyvinylchloride (PVC) and no apparent relationship was found between hydrophobicity and biofilm formation.

Staphylococcus spp. is a major cause of infections associated with urinary catheterization and other medical devices. Biofilm formation is an important step in the pathogenesis of these Staphylococci and depends on the expression of the icaADBC operon involved in the synthesis of a polysaccharide intercellular adhesion. In this study, forty-four (44) Staphylococcus spp. obtained from urinary catheters at the University Hospital of Tlemcen (North-West Algeria) were analyzed to investigate the presence or absence of the intercellular adhesion icaA and icaD genes, using the polymerase chain reaction (PCR). Phenotypic biofilm formation was examined by tissue culture plate (TCP) and Congo red agar (CRA) methods. Seventeen (17) of 44 isolates were shown to carry ica-specific DNA, 18 produced slime on CRA plates but only eight produced biofilm spontaneously on the polystyrene surfaces, under normal growth conditions. Upon induction by sugar, biofilm formation could be stimulated in seven (7) of nine (9)ica positive. Biofilm-negative isolates indicated that the icaADBC expression was down-regulated in these strains. Staphylococcus strains isolated from urinary catheters showed high levels of resistance to penicillin (98%) and gentamicine (75%). The data obtained shows the important role of ica-genes, the phenotypic variability of biofilm formation and the multi-resistance to antibiotics as virulence factors of staphylococcus spp. from urinary catheters.It confirms the complexity and diversity of regulation mechanisms implicated in biofilm formation.

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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