[Compared viability of planctonic bacteria and bacteria in biofilms by flow cytometry]. / Comparaison de la vitalité des bactéries libres et des bactéries en biofilm par cytométrie en flux.

Study of biofilms adhering to various surfaces shows the presence of several layers of cells. A small percentage can grow immediately. Are the others viable? These cells are in a resting phase and exhibit a metabolic gradient through the depth of the biofilm. In order to assess the health hazard of active recovery of these resting cells, we studied biofilms with two fluorochromes: a fluorescein diacetate derivative, CDF, which detects esterase activity and gives a green fluorescence to cells, and propidium iodide, IP, which enters cells with injured membranes and gives a red fluorescence to nucleic acids. Confocal microscopy can be used to localized red and green cells at various depths in biofilms but flow cytometry is necessary for a semi-quantitative analysis. We focused on parameters required to obtain valid flow cytometry results. After elimination of bacterial and glycocalyx autofluoresce and choosing non-toxic marker concentrations flow cytometry revealed a large proportion of double-marked cells, i.e. cells exhibiting esterase synthesis and membrane injuries. The question is whether these cells are a public health hazard. Can these cells repair their injuries and recover viability when they leave the biofilm? Do they recover metabolic activity, virulence, and sensitivity to antibacterials? Flow cytometry enabled the identification of four levels of viability in oral streptococci biofilms.

Evaluation of biohazards in dehydrated biofilms on foodstuff packaging.

Plastic materials used for food packaging are clean but not sterile when the food is just packaged. Accidental wet contamination may occur at every moment between packaging and opening by the consumer: on polyethylene (PET), bacteria may adhere strongly and constitute a biofilm in less than 24 h. By rolling on themselves, PET sheets may contaminate food. We tried to show that contact with salted foodstuffs favoured microbial recovery. Four strains were chosen to perform biofilms on PET: Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa and Escherichia coli. Biofilms were dried up 24 h. Biofilm bacteria were stressed by adhesion, by starvation and by dehydration. However, they were capable of recovery in salted solutions or media, probably because one (or more) stress protected them against another stress. Stress was demonstrated by stress protein production, by mean of electrophoresis, and membrane lesions by mean of flow cytometry. Stress recovery was performed in aqueous salted solutions or salted brain-heart infusion with NaCl 9, 15, 20 and 30 g/l. Staphylococci were more sensitive to these stresses and recovery was a function of salt concentration. Gram-negative bacteria were little affected by stresses; salt effects were less important. If all these biofilms were capable of recovery from stresses in salted media, flexible PET could possibly lead to a health hazard when it is used for wet salt meats, e.g.

[Infection on foreign material: bacterial colonization of ureteral endoprostheses]. / Infection sur matériel étranger: colonisation bactérienne des endoprothèses urétérales.

Infection on foreign body: bacterial colonization of ureteric stents. The most frequent cause of the early removal of ureteric endoprostheses (double J) is generally due to bacterial colonization. In order to prevent or to restrict the prosthesis colonization, it is necessary to understand the major steps and the factors influencing the colonization. This is the reason why we aimed to extract the most relevant parameters influencing the bacterial colonization from the observations made in vivo thanks to in vitro analyses. We have studied in vivo the relationship between the bacterial colonization of the endoprostheses, the urinary infections and the antibiotherapy. In vitro, we have defined the conditions promoting the primary adhesion of the most frequently isolated bacteria on endoprostheses. Surface properties of bacteria and materials have been compared to:--the bacterial count of infected double J samples with respect to bacterial species,--the bacterial count of the infected samples with respect to pH and Ca2+, Mg2+ concentration. The results show a great variability of the biomaterial surface properties which could be optimized, the fact that the urinary medium acidification could lower the bacterial adhesion and the ambiguous role of Ca2+ and Mg2+ ions which is discussed in this paper. In the case of in vivo analyses, the conflicting results between leukocyturia and bacteriuria lead to the detection of the bacterial colonization under antibiotic treatment. The characterized urinary infection must warn the risk of pyelonephritis.

[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.

[Comparison of the activity against Streptococcus mutans of a chlorhexidine-based antiseptic as a suspension or as a biofilm]. / Comparaison de l'activité d'un antiseptique à base de chlorhexidine sur Streptococcus mutans en suspension et en biofilm.

When bacteria colonize a surface they form a biofilm whose susceptibility to anti-microbials is different from that of the same bacterial species forming a homogeneous suspension in a liquid. This study investigated colonization of an inert solid phase (Tygon) with Streptococcus mutans ATCC 25,175--one of the strains involved in the initiation of cariogenic dental plaque--in a continuous flow of fresh medium sufficiently diluted so as to preclude growth of suspended bacteria. Only those bacteria which adhered to the solid phase grew, forming a biofilm. The antiseptic activity of Eludril (0.1% chlorhexidine) on this biofilm under dynamic (flowing medium) and static (stagnant medium) conditions was studied by comparison with the same strain in a suspension (in compliance with the AFNOR NF T 72-150 norm) and in a confluent culture on a filtering membrane. The biofilm was less susceptible under dynamic than under static conditions; under both conditions, the biofilm was less susceptible than the suspension. According to this model, the concentration of antiseptic recommended by the manufacturer according to studies using AFNOR norm NF T 72-150 (bacteria in a suspension) may be inadequate for bacteria adhering to tooth surfaces or gingival mucosa.

[From the mixed dentition to the permanent dentition: how to manage space while guiding eruption?]. / De la denture mixte à la denture permanente: comment gérer l'espace en guidant l'éruption?

In the mixed dentition, when there is a discrepancy between the bony structures and the teeth, in certain cases, serial extractions are performed in order to guide the eruption of permanent teeth and obtain a correct occlusal function. The treatment consists in the extraction of primary teeth and then of first bicuspids. The choice of the first tooth to be extracted is based upon the position of the crowns of the permanent teeth and their degree of root maturation. Then the first bicuspid is extracted as soon as or prior to its eruption. This interceptive treatment has limited indications which need to be respected in order to preserve the child's future dental health. This treatment is indicated for Class I malocclusions with severe crowding or moderate crowding associated with bi-maxillary protrusion.

[The deciduous tooth: therapeutic choices]. / La dent temporaire: les choix thérapeutiques.

Deciduous tooth diagnostic and treatment plan put a specific problem down. Therapeutical choice depends, not only of the child general health, but also of the deciduous tooth physiological period, its pathology, and the young child cooperation. Complexity of deciduous tooth biological cycle gives necessary, for the pedodontist, accuracy and a good clinical sense.

[Local anesthesia for children: a critical step]. / Anesthésie locale chez l'enfant: une étape décisive.

To realise a good child's dentistry, an excellent analgesia is primordial. Local anaesthesia is most useful for reliable and complete dental care on one tooth during one single appointment. But the young patient is afraid by the "ting", making an association with disagreeable or sore souvenirs as a vaccination. First contact with the dentist is the very important; from psychological point of view, situation has to be dedramatized; from technical point of view, anaesthesia has to be not painful and efficacious. In pedodontics, the best technical procedure is an infiltration anaesthesia.

[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.