Pseudomonas are a group of 191 species of bacteria that do not have a cell wall and thrive in an oxygen environment. Most are harmless and are commonly used in medical research, but one species, pseudomonas aeruginosa, is an opportunistic pathogen that thrives in damaged tissue and the immunocompromised, as well as being tolerant of oxygen poor environments. It also thrives in moist environments, making it a threat to most types of hospital equipment and warm wet environments like hot tubs.
P. aeruginosa commonly infects the airways, urinary tract, burns and wounds. It can lead to pneumonia, sepsis and even necrosis of the digestive tract. It is the most common infection among patients who use catheters.
Luckily, p. aeruginosa is fairly easy to diagnose as it grows readily in blood cultures and is easy to identify through gram staining and it's unique odor in culture media. Luckily, in most cases, it will self resolve, but if it is found in a site where infection is uncommon, like the bones, blood or deep tissue, aggressive treatment is usually required. Antibiotics should be avoided whenever possible as p. aeruginosa has remarkable natural resistance to most antibiotics and over-agressive use of antibiotics can lead to the development of evolved resistant strains. In most cases, antibiotics should be injected rather than given orally or intravenously.
Good hygiene habits are the best defence, including proper control of warm water environments and proper cleaning of contact lenses.