[In vivo and in vitro analysis of the ability of urinary catheter to microbial colonization]. / Analyse in vivo et in vitro de l'aptitude á la colonisation microbienne des sondes urinaires.

Bacterial adhesion to biomaterials is a complex phenomenon involving numerous factors. The ability to reduce urinary catheters infections simply by general hygiene and asepsis is low: an ascending colonization cannot be avoided. This will lead to a clinical infection only if several factors favour the bacterial adhesion or the bacterial coaggregation and the feeding of the bacterial biofilm. Among the many factors involved in bacterial adhesion, we focused in this paper on the physical parameters of surface hydrophobicity of the urinary catheters (Van der Waals and acido-basic forces) and the surface hydrophobicity of the bacteria (BATH and zeta potential). We also compared scanning electron microscopy (SEM) of in vivo and in vitro infected urinary catheters. We provided evidence that the more hydrophobic the bacteria, the more they are able to colonize hydrophobic materials, whereas hydrophilic cells are able to colonize hydrophilic materials more easily. Some biomaterials were found to display an irregular texture of hydrophobic and hydrophilic areas: they favour both types of adhesion. Moreover the divalent cations (MgII) drastically increased the bacterial coaggregation and favour bacterial growth within the biofilm. Finally, an increase in urinary pH and ionic strength increases the colonization risk. Consequently, choice of urinary catheter biomaterials is essential as patient hygiene and diet in order to avoid clinical infections.

[Prevention of cariogenic dental plaque. Study of the structures implicated in the adhesion and coaggregation in Streptococcus mutans and Streptococcus sobrinus]. / Prévention de la plaque dentaire cariogène étude des structures impliquées dans l'adhésion et la coagrégation chez Streptococcus mutans et Streptococcus sobrinus.

Cariogenic dental plaque may be assimilated to a biofilm resulting from the adhesion of S. mutans, then from the coaggregation of other streptococci, or other genus. We used a static monospecific biofilm model. Supports or bacteria were treated with inhibitors before adhesion in order to clarify the nature of adhesins responsible for the primary adhesion of S. mutans and S. sobrinus on Tygon. To determine the bindings of coaggregation, inhibitors were applied on one-day-old biofilms. Analysis of effects were performed by automatic inoculator Spiral (Interscience) for microbiological methods, and by SEM JEOL 5400 LV for microscopic methods. In the aim of preventing adhesion and coaggregation, different traps were assayed:sugars, chemical inhibitors such as F- and EDTA salts. Of these, only the latter showed efficiency. This confirmed the role of bivalent mineral ions and electrostatic attraction forces in the adhesion and coaggregation of streptococci.

[Synergism of the combination of enzymes or surfactants and a phenolic disinfectant on a bacterial biofilm]. / Synergie de l'association d'enzymes ou de surfactants et d'un désinfectant phénolique sur un biofilm bactérien.

Disrupting bacterial biofilms is necessary for a wide application domains such as reusable medical devices, or systems of pipes for water or fluids in cosmetics, food and chemicals industry. Bacterial cells embedded in a biofilm are less susceptible to disinfectants than suspended cells. This property is referable to the structure of the biofilm itself. The gangue of exopolymers and the thickness of a 5-day-old biofilm of Escherichia coli (more than 200 layers of bacteria), contribute to this decrease of susceptibility. The present work deals with the release of an Escherichia coli biofilm by the sequential action of enzymes and a phenolic disinfectant on the one hand, and by the sequential or simultaneous action of surfactants and the previous disinfectant on the other hand. The decrease of bacteria count per mm2 and the Scanning Electron Microscope observations exhibited a synergic action in every case. Nevertheless, Escherichia coli biofilms quickly reconstructed even after exposition to the previous treatment.

Antiseptic activity of some antidental plaque chemicals on Streptococcus mutans biofilms.

S. mutans is one of the bacterial species involved in the initiation of cariogenic dental plaque. In situ, antiseptic activity evaluation of dental plaque chemicals is fairly difficult. A dynamic biofilm model of S. mutans on Tygon support is suitable for the quantification of antiseptic activity and the comparison of commercial chemical formulations, submitted or not to the french standards and Pharmacopea. Some of these chemicals, especially quaternary ammonia solutions, do not reduce living bacteria counts by 10E5 as AFNOR specifies. In the case of dental plaque, antiseptic activity is probably not the only relevant parameter: biofilm dissociation is rather more relevant because the dead or living bacteria adhere to the teeth, favouring the establishment of a new active biofilm. Two proceedings can be followed: support surface can be modified, or bacteria exopolymers synthesis can be inhibited to prevent cell adherence; the disruption of the biofilm glycocalyx can be achieved with enzymes or surfactants.

[An epidemiologic survey of the prevalence of dental caries in 6-15-year-old children in Champagne-Ardennes]. / Enquête épidémiologique sur la prévalence de la carie dentaire chez les enfants de 6 à 15 ans en Champagne-Ardennes.

An epidemiological survey of dental caries in Champagne-Ardennes was conducted on a representative sample of 507 schoolchildren aged 6 to 15 years. The dft, DMFT and DMFS indices were analyzed in urban and rural zones. Although slightly lower, they were quite similar to the indices obtained at the national level. The DMFT and DMFS comparison between girls and boys showed the existence of various critical periods where a sudden and important increase in carious lesions was observed. The analysis of the indices assessing the periodontal conditions underlined the necessity of improving the oral education and hygiene.

Immunohistochemical localization of type IV collagen in mouse tooth germ: an ultrastructural study.

Localization of type IV collagen was analyzed at the ultrastructural level in mouse embryonic molars by using a preembedding technique. Cryostat sections were incubated with type IV collagen antibody and then treated with the peroxidase-antiperoxidase complex. This antibody was visualized at the epithelio-mesenchymal interface. Labeling was intense and uniformly distributed throughout the basement membrane. However, it was mainly restricted to the lamina densa. No immunostaining was detectable in the lamina lucida but it was crossed by fine filaments that appeared as projections from the lamina densa to the epithelial cell plasma membrane. At the mesenchymal aspect of the basement membrane, projections of labeled material extended from the lamina densa in the underlying dental mesenchyme. At the presecretory stage of odontoblasts, these projections were in close connection with mesenchymal cell processes.