The blue pus bacillus is the basic pathogen of human infectious disorders caused by pseudomonads. The microorganism can be isolated from the intestines of 5% healthy people and up to 30% hospitalized patients. The bacillus can be found actually everywhere, it can be isolated from soil, water, plants and animals. It is able to survive in water for about a year (at 37 °C). Sometimes it is a part of normal human microflora. It can be found on the grain skin, armpit skin and ear skin with healthy individuals (up to 2% people), on the nasal mucous membrane (about 3%), in the pharynx (about 7%) and in the digestive tract (3-24%). Patients with disturbed barrier systems and resistance factors are at a much higher risk for the infection caused by the blue pus bacillus. Pseudomonas aeruginosa contamination gives rise to 15-2-% nosocomial infections. The bacillus is believed to be one of the basic pathogens of nosocomial pneumonia (about 20%), is responsible for one-third of all urogenital disorders with urogenital patients and is thought to cause 20-25% purulent surgical infections and primary gram-negative bacteriemia. The blue pus infection can often be observed with patients who have burns or bladder disorders, especially with patients who have been taking antibiotics long enough which is accounted for by the resistance of the pathogen. It is a distinct chemoorganotroph and a strict aerobe. Like other aerobes, it synthesizes cytochrome oxidase (indophenol oxidase). Pigment formation is a specific sign of great diagnostic importance (with 70-80% clinical isolators). The phenazine pigment pyocyanine colours the nutrient medium wound discharge and bandaging material blue-green. Toxin formation. The pathogenic effect is accounted for by the formation of substances, which have exotoxin properties, and by the release of endotoxins with the destruction and disintegration of the bacterial cells. Clinical manifestations. High invasiveness is not typical, however, the ubiquitous prevalence of the bacillus (especially in hospitals) makes it the basic pathogen of wound infections and complications. The infections, especially those that occur in the hospitals run a grave course, and septicemia turn out to be fatal for 35.075% patients.