What You Need to Know About Pseudomonas Aeruginosa (PA)

Pseudomonas Aeruginosa, commonly referred to in the cystic fibrosis community as simply "PA," is one of the most prevalent and difficult pathogens to eradicate. As an opportunistic pathogen, this bacteria takes hold mostly in people who are in weak health, or are already fighting another type of infection. In people who have normal immune systems and are otherwise healthy, P. aeruginosa will not affect them. P. aeruginosa is often referred to as a "water bug" because of it's ability to survive and grow in moist environments. Whirlpools, jacuzzis, and public swimming pools are likely places for P. aeruginosa. to grow.

P. aeruginosa infections can occur anywhere in the body. Cystic fibrosis patients are particularly susceptible to acquiring P. aeruginosa infection in the lungs. Patients who are undergoing intravenous antibiotic therapy, are on a respirator, or have chronic bouts of pneumonia or bronchitis are at greater risk of contracting PA. 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.

P. aeruginosa can produce a number of toxic proteins which not only cause extensive tissue damage, but also interfere with the human immune system's defense mechanisms. Part of what makes PA so strong is that it has very little requirements in order to live. It readily adheres itself to the body's cells. This increases the risk of the infection reaching multiple systems within the body as the infected cells are transported. Additionally, P. aeruginosa doesn't need much food to survive. Even in a body that is already severely depleted and immunocompromised, PA can live. It should also be noted that P. aeruginosa is a common problem in hospitals. Because of its ability to survive, proper contact precautions and cross-infection protocol should always be used by patients and caregivers.

Perhaps the biggest challenge in treating PA is that it is resistant to many antibiotics. Medications that doctors often use as their first defense in treating lung infections in CF, such as ciprofloxacin, have little or no effect on PA. There are two forms, mucoid and non-mucoid P. aeruginosa. In the mucoid form, the bacteria has an even stronger outer-coating, making it difficult for antibiotics to penetrate the cell to kill the infection. Furthermore, the mucoid form is able to survive and reproduce more readily than the non-mucoid form. The mucoid form is what leads to more chronic respiratory infections in cystic fibrosis,

Treating an infection may involve using inhalation therapy, oral antibiotics, intravenous antibiotics, or some combination thereof. Most often doctors will treat a PA infection by prescribing "cocktail" or combination of intravenous antibiotics in the hopes that the benefits of each antibiotic will combine to produce what's called a synergistic effect. Medications utilized for this purpose include ceftazidime (Ceftaz, Fortaz, Tazicef), ciprofloxacin (Cipro), imipenem (Primaxin), tobramycin (Nebcin), ticarcillin-clavulanate (Timentin), or piperacillin-tazobactam (Zosyn). A full course of antibiotics usually lasts from 4 to 6 weeks. Studies have demonstrated that a combination of respiratory therapy (such as inhaled Tobramycin or Ceftazadime) combined with intravenous therapy, works best to deliver the medication to where infected mucus is produced, and where it later resides in the airways.

Many cystic fibrosis patients who have not been infected by P. aeruginosa, are prescribed prophylactic (preventive) antibiotic therapy. Azithromycin for example, is one such medication that has been researched in accordance with the Cystic Fibrosis Foundation, and has demonstrated positive results in improving the lung function of patients infected by P. aeruginosa. Further studies are being done to determine how well Azithromycin will reduce the instances of infection caused by P. aeruginosa. Currently there are studies being carried out to develop a vaccine for PA.



Supporting links:

Cystic Fibrosis Foundation: Azithromycin

Inhibition of PA using Azithromycin and other macrolide Antibiotics

Todar's Online Textbook of Bacteriology, "Pseudomonas" (2004)

Heatlh A to Z: Pseudomonas Infections

Eradication of Pseudomonas Aeruginosa in Cystic Fibrosis

Microbe Magazine "PA Resists Antibiotics"

Acquisition of PA in Children with CF