P. aeruginosa (Pseudomonas aeruginosa) is one of the main pathogens of purulent inflammatory processes, especially in a hospital. The first description of a wound infection caused by Pseudomonas aeruginosa belongs to Luke (1862), who noted a characteristic blue-green colouration. The first outbreak of hospital infection caused by P. aeruginosa was recorded in 1897.

P. aeruginosa is ubiquitous, water in which it can survive for up to a year (at 37 ° C), including in many solutions used in medicine (for example, liquid for storing lenses of contact). Sometimes it is part of the normal microflora (groin skin, axillary region, ears, nose, pharynx, gastrointestinal tract). P. aeruginosa causes up to 15-20% of all nosocomial infections.

The Gram-negative bacilli, mobile, have 1-2 polar flagella, in a smear are located individually, in pairs, in short chains, synthesize a substance similar to starch like extracellular mucus, more virulent strains synthesize one increased amount. It grows well on simple nutrient media, has a limited need for nutrients. It grows in a wide range of temperatures (4-42 ° C). Pronounced chemoorganotrophic, strict aerobic, highly expressed proteolytic activity, weak saccharolytic. It produces bacteriocins - pyocins (proteins that have a bactericidal effect on similar or genetically related microorganisms). Pigmentation is characteristic. The most common are: pyocyanin (colors the medium between the wounds in blue-green), fluorescein (fluorescence under UV irradiation). Certain strains can synthesize other pigments. Highly virulent strains synthesize pyocyanins with bacteriocin properties in large quantities. When isolating cultures, atypical non-pigmented strains can be observed.

The pathogenic effect is due to the formation of exotoxins and the release of endotoxins during cell death. It produces the following exotoxins: exotoxin A - disrupts the organization of the protein synthesis matrix, exoenzyme S - causes deep pathological processes in the lungs, cytotoxin - causes neutropenia and cytolysis of other cells , hemolysins, phospholipase. The enterotoxic factor (possibly responsible for the development of diarrheal syndrome), the permeability factor, neuraminidase (disrupts the metabolism of neuraminic acid), proteolytic enzymes (proteases, collagenase) are important among vital products.

It has flagellar O and H somatic antigens; capsular K antigen can be found in mucoid strains.

Despite the presence of a large number of virulence factors, infections are rarely observed in individuals with normal resistance and intact anatomical barriers. Most strains have surface villi ensuring adhesion to the epithelium. Interaction with cells is carried out through receptors, a certain role is played by the mucus produced. Attachment stimulates the fibronectin deficiency seen in cystic fibrosis and other chronic lung diseases. A typical extracellular parasite, reproduction is directly due to the ability to resist the action of resistance factors [1]. The main role in the pathogenesis of lesions is played by the toxins of the pathogen.

The highly invasive character is not characteristic, the course of infections is severe, sepsis is pronounced fatal. According to a multicenter study on the Gram-negative causative agents of nosocomial infections in ICU in USA, P.aeruginosa represented 18% of all the selected strains (second place after E. coli) [2]. It is one of the main agents responsible for nosocomial pneumonia, lesions of the genitourinary system in urological patients, causing 20 to 25% of purulent surgical infections and primary Gram-negative bacteremia. Often found in patients with burns, bladder disease. Factors of infection: violation of the rules of sterilization, storage and use of vascular and urinary catheters, lumbar puncture needles, as well as the various solutions used in medicine [1].

Pseudomonas infection is suspected by the characteristic staining of wounds, blue-green dressings. The culture method is used to highlight the identification of the pathogen. Material sampling should be done before the start of antibiotic therapy. It grows on simple nutrient media, in particular, Muller-Hinton agar is used. By developing on solid supports, it gives a characteristic phenomenon of rainbow lysis, which develops spontaneously; when the pigment forms, it stains certain supports in green. The pyocyaninotyping method is used, based on the fact that the strains are resistant to their pyocyanin and have a different sensitivity to pyocyanins from other strains. On liquid media, they give growth in the form of a surface film, over time a turbidity forms, propagating from top to bottom.

Infections caused by Pseudomonas aeruginosa are difficult to treat due to its multiple resistance transmitted by R plasmids. Mechanisms of resistance: blocking the transport of drugs to the intracellular target (anatomical characteristics of surface structures) and inactivation by enzymes (beta -lactamases inactivate penicillins and cephalosporins, acetyltransferase and nucleotidase inactivate aminoglycosides). In the multicenter NPRS-3 study, Pseudomonas aeruginosa was characterized by a very high level of resistance to gentamicin (61.3%), as well as to piperacillin, piperacillin / tazobactam, ciprofloxacin. The most active against P.aeruginosa were amikacin (resistance 6.7%) and ceftazidime (resistance 11.2%), meropenem (resistance 3%) [3].

The causative agent is resistant to antiseptics and disinfectants, can be stored in furatsilin solutions, is able to neutralize certain disinfectants, is sensitive to drying, to substances containing chlorine, to high temperatures and to pressure. The Aerugen vaccine is designed to prevent infections caused by Pseudomonas aeruginosa, developed by Berna Biotech and Orphan Europe for use in patients with cystic fibrosis. The new vaccine is expected to hit the market in 2005 and worldwide sales are expected to reach US $ 18-30 million. The main thing in preventing nosocomial infections is compliance with aseptic and antiseptic rules.