Pseudomonas Aeruginosa

Pseudomonas aeruginosa , otherwise known under the name of bacillus pyocyanic , is a Gram-negative Bactérie of the Pseudomonas . The bacilli are fine, right and very mobiles thanks to a polar Flagelle: ciliature monotriche, deprived of spores and capsules. They appear most of the time isolated or in diplobacilles.

It is Pathogène and frequently met in the infections nosocomiales.

Germinate Ubiquitaire, alive in moist environment (taps, stoppers), very resistant to many disinfectants, frequent in hospital medium, involving the appearance (because of its resistance to antibiotics) of true stocks of hospital.

The forms of Pathologie which it generates are varied: Infection of the eye, the Wound S especially Burn S and operational wounds, of the Urine S (especially after surveys), of the Lung S (for example after Bronchoscopy), of the Meningitis S of inoculation, of the Septicaemia S like final stage of serious infections or complication at patients subjected to a treatment Immunodépresseur, Leukaemic S, etc…

Etymology

The word is composed of the Greek pseudo , “imitation” or “imitation”, and monas , “unit”. One employed it in the beginnings of microbiology to indicate the " germs ". Aeruginosa , which wants to say Vert-de-gris in Latin (the result of the corrosion of copper), refers to a pigment which this bacterium contains.

Identification

Like others Pseudomonas , P. aeruginosa secretes a certain number of pigments: inter alia pyocyanin (blue-green), fluorescein (fluorescent yellow-green) and the pyorubine (brown-red). In vivo it secretes also a Biofilm, principal agent of its resistance. It is a negative bacterium lactose, i.e. deprived of enzymes degrading the Lactose, equipped with a grape odor In vitro . A preliminary recognition in laboratory identifies its colonies on the Gélose S of the type MacConkey (géloses containing inter alia lactose) to their appearance of beige pearls, whereas the colonies of positive bacteria lactose are pink. For a assured identification one seeks the presence of the enzymes of the type Oxydase (élastase and Protéase among others) that this bacterium secretes. Production of the two pigments pyocyanin and fluorescein, and the temperature of optimal growth of 42°C confirms the identification. (! Sometimes the germ does not have pyocyanin nor even of fluorescein characteristic of the fluorescent group ---> not to base itself solely on the aspect of the culture; for the growth with 42°C, it is always necessary to make a pilot boullion with 37°C because the stock can be dead and, without witness, one could believe that the test of growth to 42°C is negative whereas makes the germ of it died). P. aeruginosa uses whip for mobility, of the systems introducing of the proteins effector into the host cells, and a lipopolysaccharide which removes the immunizing responses of the hosts in addition to intervening directly in the establishment of persistent infections. Among secretions of P. aeruginosa one thus finds proteins (élastase and Protéase) which destroy the integrity of fabrics of the host by degrading their proteins such as the elastin, the Collagène and them. One finds also toxins of weak molecular weight like pyocyanin, affecting various types of sites in the host cell.

P. aeruginosa also causes microbial corrosion in the diesel and the fuel of aviation (micro-organisms using carbohydrate). It creates dark gelatinous masses sometimes called wrongly " algues".

P. aeruginosa is a bacterium very robust, naturally very resistant to the Antibiotiques and adapting quickly to the medicamentous attacks. Thus, without selection nor reinforcement by former antibiothérapies, it will not be often sensitive to some antibiotics: Ticarcilline with Acid clavulanic, Gentamicin, Ciprofloxacine, Ceftazidime, and Pipéracilline only or with addition of Tazobactam. If the infection occurs at a patient who recently received several antibiotics, the bacterium will be probably even more resistant and all the more dangerous. The resistance of P. aeruginosa to antibiotics was partially allotted to pumps of flow in its biofilm, expelling the antimicrobic components actively.

At the plants, P. aeruginosa armature of the symptoms of soft rot (software belch) at Arabidopsis thaliana cress and the lettuce ( Letuca sativa ). It is a powerful disease-causing agent at Arabidopsis and certain animals: Caenorhabditis elegans , Drosophila and Galleria mellonella . Associations of factors of virulence are the same ones for the vegetable and animal infections.

Contagion

This bacterium seems to be able to be conveyed by water, the air and particles (dust) or surfaces contaminated (Fomite S).

Its medium of development: the Biofilm

P. aeruginosa , like some other gram-negative bacteria, secretes Agrégat S structured, sometimes called biofilms, or stamps made up of complex polysaccharides in which fit the bacteria. These biofilms forms a physical barrier against the entry of antimicrobic agents. The formation of and by the biofilm is controlled by signals of cell-with-cell, and mechanisms of Quorum sensing, based on the concept of perception of the quota (" quorum sensing") and of Critical mass : the nature and thus the function of the molecules announcing the exchanges of cell-with-cell change starting from a given concentration of the bacteria. The bacteria surrounded by biofilm are less active métaboliquement thus less receptive with the antimicrobic agents and environmental disruptions.

P. aeruginosa and salicylic acid

The Salicylic acid is a phenolic metabolite produced by the plants. He plays a part in particular in the induction of answer of defense of the plants against pathogenic attacks. Working with the plants Arabidopsis thaliana and Caenorhabiditis elegans , Cryz and Al (1984) of March 14th, 2007 relating to the conditioned criteria of water quality, on the treatments and mentions of labelling private individuals of natural mineral water and of source conditioned as of natural mineral water distributed in public refreshment bar for Pseudomonas aeruginosa a number of zero bacteria by 250 ml imposes on emergence and during marketing (analyzes to begin at least three days after the taking away with collecting, conditioning, with samples preserved at temperature) ambient.

Infection with Pseudomonas aeruginosa

It is possible to contract an human infection with Pseudomonas aeruginosa. It is in general about a hospital germ responsible for infection nosocomiales, but he also meets into ambulatory among sick patients of the Mucoviscidose.

References

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