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Biology LibreTexts Pseudomonas aeruginosa

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    Pseudomonas aeruginosa

    This colorized version depicts a scanning electron micrograph (SEM) of a number of Pseudomonas aeruginosa bacteria. ("Pseudomonas aeruginosa" by Microbe World is licensed under CC BY-NC-SA 2.0)


    •  Pseudomonas aeruginosa is a Gram-negative rod motile by a polar flagellum
    • Can respire using oxygen (aerobic) or nitrate (anaerobic) as the terminal electron acceptor
    • Oxidase and catalase positive
    • Produces blue/green pigments (Figure \(\PageIndex{1}\))
    • Sometimes said to produce a fruity, grape-like smell
    • Extermely metabolically versatile; able to use a wide array of carbon and energy sources
    • Can grow in very low nutrient environments
    • Highly antibiotic resistant (Figure \(\PageIndex{1}\))



    Figure \(\PageIndex{1}\): Kirby-Bauer plate testing for antibiotic resistance in a pyoverdine (pigment)-producing Pseudomonas aeruginosa (upper left).  Note that P. aeruginosa is much more antibiotic-resistant (smaller zones of inhibition) than the other tested species. (2009.



    • P. aeruginosa can grow in almost any moist environment in temperatures from refrigeration to 42 degrees Celcius
      • One reason for banning flowers in hospital units is their ability to harbor P. aeruginosa
      • Bathing implements (such as loofahs, wash cloths, and brushes) can harbor P. aeruginosa if not allowed to dry completely between uses
      • Because of tolerance of high temperatures, can surive in hot tubs
    • Commonly found in soil and water and rarely in human intestinal flora (~3%)
      • upon hospitalization, this can increase to ~20%


    • P. aeruginosa can enter the body from the environment in any number of ways, such as by inhalation or damaged skin


    • Opportunistic pathogen
    • People with a weakened immune system, especially in health care facilities or with immune disorders such as AIDS, are at risk for severe P. aeruginosa infection
    • Commonly associated with pneumonia and other respiratory infections in cystic fibrosis (CF) patients
      • CF is a genetic disorder which causes mucus accumulation in the lungs
      • CF patients cannot clear P. aeruginosa from their lungs, and there is some evidence that the mucus acts as a food supply for the P. aeruginosa
      • Infection with P. aeruginosa can substantially decrease life expectancy for someone with CF;  Life expectancy is already just 30-40 years (
    • Burn victims are also particularly susceptible to P. aeruginosa infection
    • People without specific risk factors can also get infections, usually minor such as swimmer's ear or rash

    Clinical Disease

    • P. aeruginosa can infect alomost any tissue depending of the immune state of the patient and site of introduction
    • Some of the most common serious infections are:
      • Respiratory infections (particularly in CF patients)
      • Bacteremia/septicemia
      • Bone/joint infections
      • Urinary tract infections
      • Eye infections
    • Some infections experienced by people without specific risk factors
      • external otitis, including "swimmer's ear"
        • predisposing conditions include injury, inflammation, or simply wet and humid conditions
      • skin infections
        • often located in moist areas of the body such as feet (particularly athletes, hikers, and military), perineal region, under diapers
        • associated with hot tub use
        • can be introduced into small abrasions during use of contaminated bathing implements (such as loofahs, wash cloths, and brushes)
        • very common and serious in burn victims
    • P. aeruginosa can be very difficult to treat due to its extensive natural antibiotic resistance

    Clinical Disease

    • Biofilm formation: in most cases P. areuginosa is only virulent when living as a biofilm
    • Polysaccharide capsule: prevents phagocytosis
    • Pili for adherence
    • Pyocyanin: pigment with toxicity to various types of cell
    • Hemolysins (exotoxins which kill red blood cells) and leukocidins (exotoxins which kill white blood cells)
    • Exoenzymes such as proteases (degrades proteins) and elastase (degrades elastin) allow P. areuginosa to invade tissues
    • Like all Gram-negative bacteria, it has LPS/endotoxin

    Additional Information: Pseudomonas aeruginosa is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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