A pseudomonas infection is caused by a bacterium, Pseudomonas aeruginosa, and may affect any part of the body. In most cases, however, pseudomonas infections strike only persons who are very ill, usually hospitalized.
P. aeruginosa is a rod-shaped organism that can be found in soil, water, plants, and animals. Because it rarely causes disease in healthy persons, but infects those who are already sick or who have weakened immune systems, it is called an opportunistic pathogen. Opportunistic pathogens are organisms that do not ordinarily cause disease, but multiply freely in persons whose immune systems are weakened by illness or medication. Such persons are said to be immunocompromised. Patients with AIDS have an increased risk of developing serious pseudomonas infections. Hospitalized patients are another high-risk group, because P. aeruginosa is often found in hospitals. Infections that can be acquired in the hospital are sometimes called nosocomial diseases.
Of the two million nosocomial infections each year, 10% are caused by P. aeruginosa. The bacterium is the second most common cause of nosocomial pneumonia and the most common cause of intensive care unit (ICU) pneumonia. Pseudomonas infections can be spread within hospitals by health care workers, medical equipment, sinks, disinfectant solutions, and food. These infections are a very serious problem in hospitals for two reasons. First, patients who are critically ill can die from a pseudomonas infection. Second, many Pseudomonas bacteria are resistant to certain antibiotics, which makes them difficult to treat.
P. aeruginosa is able to infect many different parts of the body. Several factors make it a strong opponent. These factors include:
the ability to stick to cells
minimal food requirements
resistance to many antibiotics
production of proteins that damage tissue
a protective outer coat
Infections that can occur in specific body sites include:
Heart and blood. P. aeruginosa is the fourth most common cause of bacterial infections of the blood (bacteremia). Bacteremia is common in patients with blood cancer and patients who have pseudomonas infections elsewhere in the body. P. aeruginosa infects the heart valves of intravenous drug abusers and persons with artificial heart valves.
Bones and joints. Pseudomonas infections in these parts of the body can result from injury, the spread of infection from other body tissues, or bacteremia. Persons at risk for pseudomonas infections of the bones and joints include diabetics, intravenous drug abusers, and bone surgery patients.
Central nervous system. P. aeruginosa can cause inflammation of the tissues covering the brain and spinal cord (meningitis) and brain abscesses. These infections may result from brain injury or surgery, the spread of infection from other parts of the body, or bacteremia.
Eye and ear. P. aeruginosa can cause infections in the external ear canal—so-called "swimmer's ear"— that usually disappear without treatment. The bacterium can cause a more serious ear infection in elderly patients, possibly leading to hearing problems, facial paralysis, or even death. Pseudomonas infections of the eye usually follow an injury. They can cause ulcers of the cornea that may cause rapid tissue destruction and eventual blindness. The risk factors for pseudomonas eye infections include: wearing soft extended-wear contact lenses; using topical corticosteroid eye medications; being in a coma; having extensive burns; under-going treatment in an ICU; and having a tracheostomy or endotracheal tube.
Lung. Risk factors for P. aeruginosa pneumonia include: cystic fibrosis; chronic lung disease; immunocompromised condition; being on antibiotic therapy or a respirator; and congestive heart failure. Patients with cystic fibrosis often develop pseudomonas infections as children and suffer recurrent attacks of pneumonia.
Skin and soft tissue. Even healthy persons can develop a pseudomonas skin rash following exposure to the bacterium in contaminated hot tubs, water parks, whirlpools, or spas. This skin disorder is called pseudomonas or "hot tub" folliculitis, and is often confused with chickenpox. Severe skin infection may occur in patients with P. aeruginosa bacteremia. The bacterium is the second most common cause of burn wound infections in hospitalized patients.
Belinda Rowland PhD, The Gale Group Inc., Gale, Detroit,