Pseudomonas aeruginosa is a small rod-shaped bacterium (length 1.5 - 3 µm and width between 0.5 and 0.8 µm).
In humans it is an opportunistic pathogen, which can occasionally be found in the axillary, inguinal and anogenital skin regions of healthy subjects. Under normal conditions, Pseudomonas aeruginosa was isolated in approximately 10% of human stool samples.
There are numerous virulence factors that determine its pathogenicity:
- the external lipopolysaccharide layer (LPS) protects Pseudomonas aeruginosa from the phagocytic action of neutrophil leukocytes, favors its adhesion to tissues, and decreases the susceptibility of the microorganism to the bactericidal action of some antibiotics
- mobility (flagellum) and the presence of pili, fimbriae and adhesins, in addition to LPS itself, facilitate its adhesion to tissues and mucus (respiratory infection with Pseudomonas aeruginosa is common in patients with cystic fibrosis)
- toxins of various kinds (elastase, collagenase, protease, lipase) produced by the bacterium provide for the destruction of the surrounding tissue, favoring the progression of the microorganism
- other protein toxins (exotoxin A, cytotoxin, hemolysins, pyocyanin) are implicated in virulence mechanisms
Pseudomonas aeruginosa is above all a nosocomial opportunistic pathogen; it therefore produces infections especially in hospitalized patients, prediling those that are debilitated, immunocompromised or subjected to urethral catheters, mechanical ventilation, lumbar punctures and intravenous perfusions.
In the healthy adult subject Pseudomonas aeruginosa infections are rather rare. In healthy children, Pseudomonas aeruginosa diseases are limited to local infectious processes at the site of attack: external otitis, urinary infections, dermatitis (intertrigo). In subjects immunocompromised for metabolic or hematologic diseases, for tumors, prolonged antibiotic therapy or chemotherapy, Pseudomonas aeruginosa infection can become disseminated and cause, for example, pneumonia, endocarditis, peritonitis, meningitis and severe septicemia.
Diseases caused by pseudomonas aeruginosa
Infections with Pseudomonas aeruginosa can occur in many anatomical sites, such as skin, subcutaneous tissues, bones, ears, eyes, urinary tract and heart valves. The seat varies depending on the front door and the patient's vulnerability. The symptoms of Pseudomonas aeruginosa infection therefore depend on the body site affected by the infectious process.
District concerned | Diseases and factors that predispose to infection |
| Skin | Wounds, decubitus ulcers, intertrigo, burns, surgical traumas, intravenous inoculation infections, haemorrhagic necrosis of the skin or ectima gangrenous |
Ear | External otitis of swimmers, internal otitis of diabetics |
Eye | Corneal Ulcer, Traumatic Abrasion or Trauma Operators, such as those suffered during cataract removal surgery |
Respiratory System | Tracheobronchitis, Bronchopneumonia, Necrotizing pneumonia from contaminated respirators, infections due to endotracheal intubation, adult respiratory stress syndrome, infection in patients with cystic fibrosis |
Urogenital system | Urinary tract infections resulting from catheter application or irrigation |
Digestive system | Diarrhea in children (Shanghai fever), cholera-like diarrheal forms, typhlite in leukemics, rectal abscesses in cancer patients |
Circulatory system | Methemoglobinemia, Septicemia, Endocarditis (rather rare, more common in drug addicts who take intravenous drugs). |
Nervous system | Meningitis, Cerebral Abscesses, Rash Meningitis |
Care and therapy
Also therapeutic interventions depend on the site in which Pseudomonas aerugnosa has produced infection. For example, in case of cutaneous involvement, one can reconstitute with 1% acetic acid irrigations or topical application of antibacterial agents such as polymyxin B or colistin. The correct hygiene of the affected skin areas is of particular importance: the eventual necrotic tissue must be eliminated and the abscesses drained, while in the hospital environment the accurate cleaning and disinfection of medical equipment is essential.
If systemic antibiotic therapy is required, tobramycin or gentamicin is generally used. In case of resistance to these drugs, the amikacin can be used alternatively according to medical indications.
Pseudomonas aeruginosa is taking on significant clinical importance due to its multiple resistance to various antibiotics, so it is necessary to perform in vitro sensitivity tests (antibiogram) on the strain isolated from the clinical sample.
- Among the active penicillins against Pseudomonas aeruginosa are piperacillin, ticarcillin and mezlocillin.
- Among the cephalosporins active against Pseudomonas aeruginosa we mention: ceftazidime and cefoperazone (also known as third-generation antipseudomonas cephalosporins).
- The fourth-generation parenteral cephalosporins active against Pseudomonas aeruginosa include: cefepime, imipenem, metropenem and aztreonam.
- Many active aminoglycosides against Pseudomonas aeruginosa : tobramycin, amikacin and gentamicin.
- Among fulorochinolins, ciprofloxacin appears to be the most active against the body; the antibiotic action of levofloxacin is slightly less, while the other fluoroquinolones are not at all or not very effective.
