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Pseudomonas Infections


Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University

Last full review/revision Feb 2020| Content last modified Feb 2020
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Any of several types of the gram-negative bacteria Pseudomonas, especially Pseudomonas aeruginosa, can infect different parts of the body, particularly in people who have serious medical problems or who are hospitalized.

  • Infections range from mild external ones (affecting the ear or hair follicles) to serious internal infections (affecting the lungs, bloodstream, or heart valves).

  • Symptoms vary depending on which area of the body is infected.

  • Identifying the bacteria in a sample taken from infected tissue confirms the diagnosis.

  • Antibiotics are applied externally for external infections or given intravenously for more serious, internal infections.

(See also Overview of Bacteria.)

Pseudomonas bacteria, including Pseudomonas aeruginosa, are present throughout the world in soil and water. These bacteria favor moist areas, such as sinks, toilets, inadequately chlorinated swimming pools and hot tubs, and outdated or inactivated antiseptic solutions. Occasionally, these bacteria are present in the armpits and genital area of healthy people.

Pseudomonas aeruginosa infections range from minor external infections to serious, life-threatening disorders. Infections occur more often and tend to be more severe in people who

These bacteria can infect the blood, skin, bones, ears, eyes, urinary tract, heart valves, and lungs, as well as wounds (such as burns, injuries, or wounds made during surgery). Use of medical devices, such as catheters inserted into the bladder or a vein, breathing tubes, and mechanical ventilators, increase the risk of Pseudomonas aeruginosa infections. These infections are commonly acquired in hospitals. In hospitals, the bacteria are often present in sinks, antiseptic solutions, and containers used to collect urine from a bladder catheter.


Pseudomonas aeruginosa causes many different infections.

Swimmer’s ear (external otitis) is a mild external infection that can occur in otherwise healthy people. Water containing the bacteria can enter the ear during swimming. Swimmer’s ear causes itching, pain, and sometimes a discharge from the ear.

Malignant external otitis is a more severe external ear infection. It is most common among people with diabetes. Tissues become swollen and inflamed, partly or completely closing the ear canal. Symptoms may include fever, loss of hearing, inflammation of tissues around the infected ear, severe ear pain, a foul-smelling discharge from the ear, and nerve damage.

Hot-tub folliculitis is another mild external infection. Hair roots (follicles) become infected in people who use hot tubs or whirlpools, particularly if the hot tubs and whirlpools are inadequately chlorinated. Spending a lot of time in the water softens the follicles, making them easier for bacteria to invade. An itchy rash consisting of tiny pimples develops. Pimples may have a drop of pus in their center.

Ecthyma gangrenosum is a skin sore that occurs in people who have too few white blood cells (neutropenia). The sore has a purple-black center and is surrounded by a band of red. These sores usually occur in moist areas, such as the armpit or genital areas.

Eye infections due to these bacteria may damage the cornea, often permanently. Enzymes produced by the bacteria can rapidly destroy the eye. Infections usually result from injuries but may result from contamination of contact lenses or contact lens solution.

Soft-tissue infections include those in muscle, tendons, ligaments, fat, and skin. These infections can occur in deep puncture wounds (for example, stepping on a nail). Pseudomonas bacteria can also infect pressure sores, burns, and wounds due to injuries or surgery. When these bacteria grow in soiled dressings, the dressings turn green and smell like newly mowed grass. Fluids draining from these wounds often have a sweet, fruity smell.

Severe pneumonia can develop in hospitalized people, especially those who need to use a breathing tube and a mechanical ventilator. In people with HIV infection, Pseudomonas bacteria commonly cause pneumonia or sinus infections.

Urinary tract infections usually develop in the following circumstances:

  • After a procedure involving the urinary tract is done

  • When the urinary tract is blocked

  • When a catheter must remain in the bladder a long time

Bloodstream infections (bacteremia) often result when the following occur:

  • Bacteria enter the bloodstream from an infected organ (such as the urinary tract).

  • A contaminated illegal drug is injected into a vein.

  • A contaminated needle or syringe is used to inject illegal drugs.

  • A catheter in a blood vessel (called an intravascular catheter) is left in place.

Sometimes the source of the bacteria is unknown, as may occur in people who have too few white blood cells after cancer chemotherapy. Purple-black spots surrounded by a red rim on the skin (ecthyma gangrenosum) often develop in the armpits and groin. Without treatment, a bloodstream infection can lead to shock and death.

Bone and joint infections usually occur in the spine, pubic bone, and/or the joint between the collarbone and breastbone. The bacteria usually spread to bones and joints from the bloodstream, particularly in people who use illegal intravenous drugs. Less often, the bacteria spread from nearby soft tissues that have been infected after an injury or surgery.

Heart valve infections are rare. They usually occur in people who inject intravenous drugs and in people with artificial heart valves. The bacteria usually spread to heart valves from the bloodstream.


  • Culture of a sample of blood or other body fluids

Doctors diagnose Pseudomonas aeruginosa infections by taking a sample of blood or other body fluids and sending it to a laboratory to grow (culture) and identify the bacteria.

Tests to determine which antibiotics are likely to be effective (susceptibility tests) are also done.


  • Usually antibiotics applied topically, taken by mouth, or given intravenously, depending on where the infection is

Swimmer’s ear can be effectively treated, as well as prevented, by irrigating the ears with an acetic acid (vinegar) solution before and after swimming. Or the infection can be treated with a topical antibiotic such as polymyxin applied to the ear.

Hot-tub folliculitis usually resolves without treatment.

Eye infections are treated with highly concentrated antibiotic drops, applied frequently at first. Sometimes antibiotics must be injected directly into the eye.

Urinary tract infections that cause symptoms can often be treated with levofloxacin or ciprofloxacin, taken by mouth. If these infections do not cause symptoms, they are usually not treated.

Serious infections due to Pseudomonas aeruginosa are difficult to treat. Malignant external otitis, internal infections (such as pneumonia or heart valve infection), and blood infections require weeks of antibiotics given intravenously. Usually, one antibiotic, such as ceftazidime or ciprofloxacin, is effective. But sometimes a combination of antibiotics is required because many strains, particularly those acquired in health care facilities, are resistant to many antibiotics. Doctors initially choose an antibiotic that is usually effective in their geographic area. They may change the antibiotics after test results indicate which antibiotics are likely to be effective.

For heart valve infections, open-heart surgery to replace the valve plus antibiotic therapy is usually needed (see Replacing a Heart Valve).

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