Pseudomonas Aeruginosa Infections in Hospitals

Pseudomonas aeruginosa is a bacterium able to cause disease in plants, animals, and humans. It is a ubiquitous, multi drug resistant pathogen able to infect both immunocompetent and immunocompromised individuals. Found in human skin flora, water, and soil, it is present in man-made environments across the globe. The bacteria displays considerable versatility in what organic material it can use as food. It is able to infect damaged tissues and individuals with reduced immunity. Infection may occur in a number of different organs, while infection of critical or vital organs can prove fatal. Its ability to thrive on moist surfaces make hospital medical equipment such as catheters a prime zone of proliferation. Comparatively, P. aeruginosa is not particularly virulent, unlike strep or staph, but nevertheless is capable of extensive colonization of its host. Enduring biofilms allow the bacteria to reside on surfaces for extended periods of time. When it forms a biofilm after colonizing a human body, it can overwhelm the immune system and ultimately be fatal. This is possible in patients with cystic fibrosis and ciliary dyskinesia.

Yielding a blue-green color in lab cultures, the name ‘aeruginosa' comes from the Latin term for copper rust. Oxygen depletion is not an obstacle to this pathogenic, which is capable of anaerobic growth (growth in the absence of oxygen). Iron is the primary nutrient required for P.aeruginosa growth, however, high levels can actually be toxic to the bacterium.

P.aeruginosa is characterized as one of many opportunistic nosocomial (hospital acquired) infections that prey on immunocompromised patients, who may have just undergone surgery, antimicrobial treatment or are taking immunosuppressing drugs.

The bacteria can be identified in lab cultures by its pearlescent appearance and tortilla-like smell. It produces dark and hellish mats that resemble algae. According to the CDC, there are an estimated 51,000 nosocomial (hospital-acquired) cases of P.aeruginosa infections in the US annually.

Causes of P.aeruginosa

The bacterium is able to infect wounds, burns, the airway and the urinary tract. Depending on its point of access, it may also cause blood infections (bacteremia.) P.aeruginosa has been characterized as the most frequent colonizer of medical devices such as catheters and commonly can infect burn injuries and the outer ear. Equipment can become contaminated by the hands of health care workers and if not properly cleaned can spread the bacteria. In rare cases, P.eruginosa is the cause of ventilator-associated pneumonia.

P.aeruginosa is the culprit in one out of every ten hospital acquired infections. Prevalent in moist environments, the bacteria is a common cause of ‘hot tub rash' and swimmers ear. It is frequently associated with postoperative infection in radial keratotomies. The skin lesion ecthyma gangrenosum and osteomyelitis in foot wounds can also be caused by the bacteria.

Low phosphate levels can ‘trigger' benign symbiotic bacteria in the intestinal tract, causing them to release lethal toxins that could damage or kill its host.

Symptoms of P.aeruginosa

The symptoms of this pathogen can be nonspecific, seeing as many types of nosocomial bacteria can induce the same conditions. Symptoms will vary based on the site of infection and (i.e. UTI, ventilator-associated pneumonia, bacteremia), however, most of these conditions can be caused by a number of different bacteria. In order to conclusively determine that P.aeruginosa is the cause of a given infection, lab tests must be run. Once the causative bacteria has been determined, appropriate antibiotics can be prescribed.

Conditions that can be caused by P.aeruginosa include:

  • wound infection
    • accompanied by green blue pus
  • UTI
    • frequent urge to urinate
    • foul smelling, cloudy or bloody urine
    • painful urination
  • pneumonia
    • a cough accompanied by green, yellow or bloody phlegm
    • difficulty breathing
    • fever and chills
  • bloodstream infection (bacteremia)
    • body ache/fever/chills
    • lightheadedness
    • rapid pulse

Each of these infections is associated with its own unique set of symptoms. Other organs that can become infected with P.aeruginosa include the liver, brain, bones, and sinuses.

Risk Factors for P.aeruginosa

Opportunistic in nature, the bacteria takes advantage of a host whose immune defenses are impaired. P.aeruginosa has a notably higher incidence of infection in burn victims than other nosocomial pathogens.

General risk factors for infection by this pathogen include:

  • Mechanical ventilation
  • Cystic fibrosis
  • HIV
  • Open surgical wounds
  • Intravenous or urinary catheters
  • Chemotherapy
  • Long periods of hospitalization
  • Prolonged exposure to antimicrobial therapy

Treatment of P.aeruginosa

Nosocomial infections of P. aeruginosa are harder to treat than the community acquired skin infections which the bacteria can cause in healthy individuals. Like a number of hospital-acquired pathogens, P.aeruginosa has begun to show an increasing and troublesome degree of antibiotic resistance. The bacteria has shown resistance to all of the following:

  • Aminoglycosides
  • Cephalosporins
  • Fluoroquinolones
  • Carbapenems (last resort antibiotics that could cause severe allergic reaction)

A combination of antibiotics is usually the best course of action. In rare cases, the infected tissue may have to be surgically removed.

Antibiotics used to treat P.aeruginosa include:

  • gentamicin
  • piperacillin
  • tazobactam
  • aztreonam
  • ciprofloxacin
  • cefepime
  • tobramycin
  • meropenem
  • ceftazidime

Prevention of P.aeruginosa

Like any bacterial pathogen that has increased in prevalence and displayed antibiotic resistance, prevention and control of P.aeruginosa are a public health concern. Various prevention tactics are available and do not differ significantly from the tactics employed to prevent the spread of other antibiotic resistant bacteria.

Sterile equipment and aseptic techniques are crucial in reducing the incidence of P.aeruginosa infections, especially at the site of catheters which they have been known to colonize. Immune impaired patients are at especially high risk, therefore health care workers should be prudent about hand hygiene when interacting with such patients.

P.aeruginosa is exceptionally common in the environment, facilitating its colonization in healthcare settings. Research indicates that Probiotic prophylaxis could possibly prevent colonization and delay the onset of infections in ICU settings.

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