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.
- Urinary tract. Urinary tract infections can be caused by catheterization, medical instruments, and surgery.
- 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.
Causes and symptoms
P. aeruginosa can be sudden and severe, or slow in onset and cause little pain. Risk factors for acquiring a pseudomonas infection include: having a serious illness; being hospitalized; undergoing an invasive procedure such as surgery; having a weakened immune system; and being treated with antibiotics that kill many different kinds of bacteria (broad-spectrum antibiotics).
Each of the infections listed above has its own set of symptoms. Pseudomonas bacteremia resembles other bacteremias, producing fever, tiredness, muscle pains, joint pains, and chills. Bone infections are marked by swelling, redness, and pain at the infected site and possibly fever. Pseudomonas meningitis causes fever, headache, irritability, and clouded consciousness. Ear infection is associated with pain, ear drainage, facial paralysis, and reduced hearing. Pseudomonas infections of the eye cause ulcers that may spread to cover the entire eye, pain, reduced vision, swelling of the eyelids, and pus accumulation within the eye.
P. aeruginosa pneumonia is marked by chills, fever, productive cough, difficult breathing, and blue-tinted skin. Patients with cystic fibrosis with pseudomonas lung infections experience coughing, decreased appetite, weight loss, tiredness, wheezing, rapid breathing, fever, blue-tinted skin, and abdominal enlargement. Skin infections can cause a range of symptoms from a mild rash to large bleeding ulcers. Symptoms of pseudomonas folliculitis
Diagnosis and treatment of pseudomonas infections can be performed by specialists in infectious disease. Because P. aeruginosa is commonly found in hospitals, many patients carry the bacterium without having a full-blown infection. Consequently, the mere presence of P. aeruginosa in patients does not constitute a diagnostic finding. Cultures, however, can be easily done for test purposes. The organism grows readily in laboratory media; results are usually available in two to three days. Depending on the location of the infection, body fluids that can be tested for P. aeruginosa include blood, urine, cerebrospinal fluid, sputum, pus, and drainage from an infected ear or eye. X rays and other imaging techniques can be used to assess infections in deep organ tissues.
Because P. aeruginosa is commonly resistant to antibiotics, infections are usually treated with two antibiotics at once. Pseudomonas infections may be treated with combinations of ceftazidime (Ceftaz, Fortraz, Tazicef), ciprofloxacin (Cipro), imipenem (Primaxin), gentamicin (Garamycin), tobramycin (Nebcin), ticarcillinclavulanate (Timentin), or piperacillin-tazobactam (Zosyn). Most antibiotics are administered intravenously or orally for two to six weeks. Treatment of an eye infection requires local application of antibiotic drops.
Surgical treatment of pseudomonas infections is sometimes necessary to remove infected and damaged tissue. Surgery may be required for brain abscesses, eye infections, bone and joint infections, ear infections, heart infections, and wound infections. Infected wounds and burns may cause permanent damage requiring arm or leg amputation.
Most pseudomonas infections can be successfully treated with antibiotics and surgery. In immunocompromised persons, however, P. aeruginosa infections have a high mortality rate, particularly following bacteremia or infections of the lower lung. Mortality rates range from 15 to 20% of patients with severe ear infections to 89% of patients with infections of the left side of the heart.
Minor skin infections can be prevented by avoiding hot tubs with cloudy water; avoiding public swimming pools at the end of the day; removing wet swimsuits as soon as possible; bathing after sharing a hot tub or using a public pool; cleaning hot tub filters every six weeks; and using appropriate amounts of chlorine in the water.
Centers for Disease Control. <http://www.cdc.gov/nccdphp/ddt/ddthome.htm>.
Mayo Clinic Online. 5 Mar. 1998. <http://www.mayohealth.org>.
Belinda Rowland, PhD
Bacteremia—Bacterial infection of the blood.
"Hot tub" folliculitis—A skin infection caused by P. aeruginosa that often follows bathing in a hot tub or public swimming pool.
Immunocompromised—Having a weak immune system due to disease or the use of certain medications.
Nosocomial infection—An infection that is acquired in the hospital.
Opportunistic—Causing disease only under certain conditions, as when a person is already sick or has a weak immune system.
Pathogen—Any microorganism that produces disease.