P. aeruginosa is a germ found in the environment and it is an opportunistic human pathogen most commonly infecting immunocompromised patients, such as those with cancer, diabetes, cystic fibrosis,[1] severe burns, AIDS,[2] or people who are very young or elderly.

Complications include pneumonia, gangrene, necrotizing fasciitis, compartment syndrome, necrosis, loss of an extremity, and sepsis, which may lead to septic shock and death.

[3] Treatment of such infections can be difficult due to multiple antibiotic resistance,[4] and in the United States, there was an increase in MDRPA (Multidrug-resistant Pseudomonas aeruginosa) resistant to ceftazidime, ciprofloxacin, and aminoglycosides, from 0.9% in 1994 to 5.6% in 2002.

[8] P. plecoglossicida is a fish pathogenic species, causing hemorrhagic ascites in the ayu (Plecoglossus altivelis).

[10] Due to their hemolytic activity, even non-pathogenic species of Pseudomonas can occasionally become a problem in clinical settings, where they have been known to infect blood transfusions.