What is the pathogenesis of P aeruginosa infection?

Updated: Dec 17, 2018
  • Author: Selina SP Chen, MD, MPH; Chief Editor: Russell W Steele, MD  more...
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Answer

Although P aeruginosa is a common human saprophyte, it rarely causes disease in healthy persons. Most infections with this organism occur in compromised hosts. Examples of compromising conditions include disrupted physical barriers to bacterial invasion (eg, burn injuries, intravenous [IV] lines, urinary catheters, dialysis catheters, endotracheal tubes) and dysfunctional immune mechanisms, such as those that occur in neonates and in individuals with cystic fibrosis (CF), [1] acquired immunodeficiency syndrome (AIDS), neutropenia, complement deficiency, hypogammaglobulinemia, and iatrogenic immunosuppression.

The complete sequence of the genome of P aeruginosa strain, PAO1, is noted for its large size and diverse metabolic capacity. The pathogenesis of this organism is multifactorial and involves various toxins and proteases (eg, exotoxin A, lecithinase) and the glycocalyx "slime." P aeruginosa is both invasive and toxigenic. The 3 stages of Pseudomonas infections are (1) bacterial attachment and colonization, (2) local infection, and (3) bloodstream dissemination and systemic disease.

Efflux systems are thought to contribute to antimicrobial resistance in P aeruginosa; thus, efflux pump inhibitors are thought to be useful in reducing the invasiveness and antimicrobial resistance of P aeruginosa and may be promising as new anti-infectious agents. The genome annotation is continually updated, and the database functionality is being expanded to facilitate accelerated discovery of P aeruginosa drug targets and vaccine candidates.

Pseudomonal infection, as described by Pollack, occurs in 3 stages: (1) bacterial attachment and colonization, followed by (2) local invasion and (3) dissemination and systemic disease. [2]

In healthy children, disease is primarily limited to the first 2 stages (as in diseases such as otitis externa, urinary tract infections (UTIs), dermatitis, cellulitis, and osteomyelitis), although recent case reports describe bacteremia, sepsis, and GI infections in previously healthy children.

In immunocompromised hosts, including neonates, infection can progress rapidly through the 3 stages and cause pneumonia, endocarditis, peritonitis, meningitis, ecthyma gangrenosum (EG), bacteremia, and overwhelming septicemia.


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