Silice et auto-immunité

Autoimmune diseases are pathologic conditions defined by abnormal autoimmune response and characterized by T-cells and B-cells reactivity against self determinants. They affect approximately 5% of the population in the Western countries. Epidemiologic studies have demonstrated that susceptibility to the development of these disease is under the control of genetic determinants. However, even in genetically predisposed people, an environmental exposure or a change in the internal environment is necessary for frank auto reactivity. Microbial antigens, drugs, estrogens and occupational exposures are able for triggering autoimmune reaction. Silica and related substances such as silicates are the most abundant minerals in the earth's crust and inhalation of silica particles is a very common condition. The association of silica exposure and autoimmune diseases such as scleroderma, rheumatoid arthritis and primary vasculitides is well documented. The pathophysiology of these conditions is poorly understood.     

Infections à protozoaires et environnement

Protozoan parasites present a dispersal phase allowing spreading in the environment. Transmissive stages can be found in water, soil and food, where they can survive during long periods of time. Such parasites represent a continous threat for human and animal health. Main protozoans parasites are Cryptosporidium spp., Giardia spp., Cyclospora sp., Toxoplasma sp. as well as amœba Entamœba spp., Acanthamœba spp. and Naegleria sp. All these pathogens can be responsable for major waterborne disease outbreaks.The density of parasite contamination in aquatic environment particularly surface water and waste water begins to focus attention. Detection methods, however, have to be improved in order to be able to produce data such as viability, infectiosity and typing of the parasite stages. That are essentiel to determine the significance of the presence of these waterborne pathogens for public health.     

Pseudomonas et apparentés

Gram-negative nonfermenting rods have been for most of them initially accomodated in the genus Pseudomonas. Their taxonomic position has considerably changed as a result of successive genomic studies. They are now reclassified in new families and separate genera on the basis of phenotypic (growth parameters) and genotypic characteristics (% G+C content, DNA-DNA hybridization, 16S rRNA gene sequence analysis).For identification in clinical laboratories, the following genera, Pseudomonas, Burkholderia, Pandoraea, Ralstonia, Stenotrophomonas, Massilia, Alcaligenes, Achromobacter, Ochrobactrum, Comamonas, Acidovorax, Psychrobacter, Brevundimonas, Agrobacterium, Sphingomonas, Shewanella, Methylobacterium, Roseomonas, Chryseobacterium, Empedobacter, Myroides, Bergeyella, Weeksella, Sphingobacterium and Oligella, are classified according to a simplified approach (oxidase reaction, motility, indole production) and are described in tables giving phenotypic characteristics and growth parameters.Commercial and automatic systems are available for identification of Gram-negative nonfermenting rods, but suppose the determination of basic characters to avoid false identification.     

Diagnostic et traitement des légionelloses

Legionellosis are infections caused by Gram-negative bacilli Legionella sp. Legionella pneumophila serogroup 1 is the most pathogenic, accounting for 80% of infections. Legionella are responsible for nosocomial and community-acquired pneumonia. Disease occurs as sporadic cases or explosive epidemics. Extrapulmonary legionellosis is rare. Immunosuppressed patients are at particular risk for acquiring legionellosis. Legionnaires' disease can not be differentiated from other common causes of pneumonia, based on clinical, radiographic, or nonspecific laboratory findings. There are four currently used methods for the laboratory diagnosis of legionella infections: isolation of the organism on culture media, immunofluorecsent detection of antigen in tissues or body fluids, detection of L. pneumophila serogroup 1 anti-genuria, and seroconversion. Direct fluorecent-antibody staining and the detection of legionella urinary antigen are rapid diagnosis tests. Delay in instituting appropriate therapy significantly increases mortality. Fluoroquinolones and the newer macrolides (azithromycin, clarithromycin) seem to be now the drug of choice, because they have greater in vitro activity, better intracellular penetration, and lower toxicity than erythromycin. Treated nonimmunosuppressed patients have a case fatality rate of about 5% versus 25–30% in treated immunosuppressed patients.