Pseudomonas aeruginosa: Infections, Pathogenesis

By Acharya Tankeshwar •  Updated: 05/03/22 •  2 min read

Pseudomonas aeruginosa is a gram-negative rod. Pseudomonas aeruginosa can resist high concentrations of salt, dyes, weak antiseptics, and many commonly used antibiotics. Most pseudomonads known to cause disease in humans are associated with opportunistic infections.  Pseudomonas aeruginosa and Pseudomonas maltophila are mostly responsible for disease conditions.  

This opportunistic pathogen may infect virtually any tissue. Infection is facilitated by the presence of an underlying disease. It is a major threat to hospitalized patients, particularly those with serious underlying diseases such as cancer and burns (burning causes breakdown of nonspecific host defenses).  

Sites of infection by P. aeruginosa

  1. Central nervous system infections
  2. Localized infections of the ear and sinus
  3. Skin and musculoskeletal tissues, burn wounds, surgical wounds
  4. Respiratory tract: chronic infections in cystic fibrosis patients, acute pneumonia in other patients
  5. Bacteremia
  6. Endocarditis
  7. Urinary tract infections

Mortality in P. aeruginosa infection

Infections with P. aeruginosa are associated with a high mortality rate. This is because of the combination of

  1. Bacterial resistance to antibiotics
  2. Weakened host defenses
  3. Production of extracellular bacterial enzymes and toxins.

Pathogenesis of P. aeruginosa

Pseudomonas aeruginosa produces many factors that may contribute to its virulence. Some of them are

  1. Hemolysins: Glycolipid hemolysin may play a role in P. aeruginosa pulmonary infections.
  2. Extracellular polysaccharides: They may impede phagocytosis and impair the diffusion of antibiotics and thus facilitate colonization and persistence. These mucoid strains usually are isolated only from patients with cystic fibrosis.
  3. Pigments: Pyocyanin (a phenazine pigment) and fluorescein are two common pigments produced by P. aeruginosa. Pyocyanin retards the growth of some other bacteria and thus may facilitate colonization by P. aeruginosa.
  4. Extracellular protease: May play role in the formation of hemorrhagic lesions and tissue destruction.

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please email at

2 responses to “Pseudomonas aeruginosa: Infections, Pathogenesis”

  1. saritha kandagatla says:

    Hi Mr.Acharya
    I am a Microbiologist and i have a question about the MacConkey Broth. We incubate 10 ml of MacConkey broth with 1 ml of product for 24 hrs for detection of E.coli, and then streak it on to MacConkey Agar plate after 24 hrs of incubation. sometimes when we have a long weekend we are not able to streak it after 24 hrs. What can be done in those circumstances? Can we increase the volume of MacConkey Broth? Please do suggest what is the best solution for this kind of situation.
    Thank You

    • tankeshwar says:

      Hello Saritha Ma’am
      Happy to get your query. In our settings, we have not used MacConkey broth for such purpose so it’s hard to tell.
      What’s about running a pilot survey with some standard isolates and check the yield with varying amount/concentration of media? You can also witness up to when delayed in sub-culture do not affect the yield significantly. If the yield is increased after increasing the volume of the MacConeky broth, you can safely replicate that process later. Adopting evidence-based practice will be best, I guess.

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