Question

If a patient has a second-degree burns on the leg and then the wound showed signs of cellulitis. After few days the bandage was removed and the wound had gotten deeper, with an increase in the necrotic tissue along with a greenish-tinged pus. The patient had also developed a fever. After tests, they found out that the patient was diagnosed with a wound infection caused by Pseudomonas aeruginosa.
The patient had surgeries to remove additional infected tissues, with amputation of the limb considered as an option to save his life.
The patient was started on IV sulbactam along with colistin.
After that, the wound started to show signs of healing.
The question is :
What virulence factors produced by Pseudomonas aeruginosa would have contributed to the severity of this patient's infection?

Answer 1

Pseudomonas is a large group of aerobic non sporing Gram negative bacilli motile by polar flagella. The clinical isolates of organisms are often piliated. It is non encapsulated but many strains may have mucoid slime layer. Pseudomonas aeruginosa is the most common and serious cause of infection in burns. The preeminent role of pseudomonas in hospital infection is due to its resistance to common antibiotics and antiseptic and its ability to establish itself widely in hospitals.

The virulence factors are:-

1. Exotoxin A: it has a mechanism of action similar to that of the diphtheria toxin. It also has an active A subunit and binding B subunits. Subunit B helps in binding and A inhibits polypeptide chain elongation in the presence of NAD by inactivating Elongation Factor (EF-2). Thus inhibits protein synthesis.
2. Pili for adhesion
3. Lipopolysaccharide (cell wall) and alginate glycocalyx.
4. Enzymes and toxins like:- Proteases, elastase, hemolysins, enterotoxin.
5. Slime layer acts as a capsule.
6. Biofilm formation.