Pseudomonas is a common bacterium that causes diseases in plants, animals, and even humans. It is a genus that contains up to 140 species, most of which are saprophytic.

They are resistant to many drugs and are associated with opportunistic infections, which makes it a bacterium of medical importance.

Pseudomonas species that cause infections include P aeruginosa, P putrefaciens, P fluorescens, P maltophilia, P cepacia, P stutzeri, and P putida. Two species, P pseudomallei, and P mallei, cause specific human diseases: melioidosis and glanders. P aeruginosa is well known for its resistance to antibiotics, its ubiquity, and its association with hospital-acquired infections such as sepsis syndromes and pneumonia associated with ventilators.

Pseudomonas aeruginosa and P maltophilia account for about 80 percent of pseudomonas species recovered from clinical specimens. Due to its frequency of occurrence in humans, P aeruginosa has received the most attention.

It is a widespread free-living bacterium and is found in most moist environments such as skin flora, soil, water, and most artificial environments around the world.

Although it rarely causes disease in healthy individuals, it is a significant threat to hospitalized patients, especially those with severe underlying conditions such as cancer and burns.

A mortality rate of pseudomonas infections is due to the combination of a weak immune system, resistance to antibiotics, and the production of extracellular bacterial toxins and enzymes.

Pseudomonas aeruginosa can be found in soil, water, and vegetation. It is located in the dermal layer of the skin of some healthy persons and has been isolated from the throat and stool of non-hospitalized patients.

The amount of bacteria in the intestinal tract increases in hospitalized patients to 20 percent within 72 hours of admission.

Hospitalized patients are the population at the most risk of getting infected. While in the hospital, P aeruginosa finds many places to inhabit: food, disinfectants, taps, respiratory equipment, sinks, and mops.

Also, it is continuously reintroduced into the hospital environment on plants, vegetables, fruits, and patients transferred from other medical facilities.

Its spread occurs from patient to patient on the hands of hospital personnel, via direct patient contact with contaminated reservoirs, and by the ingestion of contaminated foods and water.

Signs and Symptoms of Pseudomonas Bacteria

Skin infections of the bacteria are usually less severe than infections that occur in the lungs or blood. Certain symptoms depend on the site at which the disease occurs.


At the point of infection, the bacteria typically affects the hair follicles, a condition known as folliculitis. Redness of the skin, draining wounds, and the formation of abscess are all symptoms of this condition.


The bacterial infection of the blood is referred to as bacteremia. This type of infection is the most severe one caused by pseudomonas bacteria. The symptoms of the infection include fever, muscle and joint pain, chills, and fatigue.

This infection can also lead to very low blood pressure, known as hemodynamic shock. This eventually leads to the failure of major organs like the liver, heart, and kidneys.


Pseudomonas bacterium can sometimes cause an infection of the external ear canal known as “Swimmer’s Ear”. The symptoms of this infection are ear pain, swelling, difficulty hearing, itching inside the ear, and discharge from the ear.


Noticeable symptoms of eye infections caused by pseudomonas bacterium include inflammation, pus, swelling of the eyes, impaired vision, redness, and pain.


Lung infection of pseudomonas bacteria is known as pneumonia. The symptoms include fever, chills, difficulty breathing, and heavy cough with or without the release of phlegm.

What are the infections caused by Pseudomonas?

Although pseudomonas is mostly associated with lung infections, they can cause a variety of infections. These include:

People with existing lung diseases sometimes carry the bacteria in their lungs without causing infection.

Who is at risk?

Healthy individuals have lower chances of being infected by pseudomonas bacteria compared to people with a weakened immune system.

People who have their immune system compromised are susceptible to pseudomonas infections. This is especially true for patients that have been in the hospital for a long time.

The bacteria can be spread in hospitals through the hands of healthcare workers or by hospital equipment and facilities that have not been properly cleaned.

Pseudomonas infections are considered to be opportunistic, this means that they only cause disease when a person’s immune system has been compromised.

Certain conditions increase one’s chances of getting infected. These include:

  • Chemotherapy treatment for cancer
  • Cystic fibrosis
  • Burn wounds
  • Surgery
  • Presence of a foreign body like ventilators and other breathing equipment.

Mild cases of the infection, such as skin rashes and ear infections, have been observed in healthy individuals. The infection might occur after exposure to swimming pools and hot tubs that not been adequately chlorinated.

Infections of the eyes occur in people that use infected lens solutions to wash their contact lenses.


The diagnosis of Pseudomonas bacteria depends on its isolation and laboratory identification. It grows well on most laboratory culture media and commonly is isolated on blood agar plates.

It is identified based on its Gram morphology and its inability to ferment lactose. It tests positive oxidase, citrate, and catalase reactions. Fluorescence under ultraviolet radiation helps in the early identification of pseudomonas colonies and also is useful in suggesting its presence in wounds.


Infections caused by pseudomonas are treated with antibiotics. However, many pseudomonas infections are becoming increasingly difficult to treat. These microrganisms have developed the ability to adapt and overcome antibiotics in their environment.

This development has made treating infections much more challenging. Pseudomonas infections can often build resistance to multiple types of antibiotics. It can even sometimes build resistance during the course of treatment.

It is important that your physician selects an effective antibiotic. A doctor may send a sample from a patient to a laboratory first for testing to be more certain. The laboratory will test the sample to determine which antibiotic will work best.

Treatment of pseudomonas infections may involve one or more of the following types of antibiotics:

  • Gentamicin
  • Carbapenems
  • Cefepime
  • Ciprofloxacin
  • Ceftazidime
  • Ureidopenicillins
  • Aztreonam
  • Ticarcillin

How to avoid getting infected?

  • Keep your hands clean to avoid getting sick and spreading germs that can cause infections
  • Wash hands with soap and water or use alcohol-based hand sanitizer, particularly before and after caring of wounds.
  • Healthcare providers should clean their hands before touching patients.