Pseudomonas aeruginosa Infections

Updated: Dec 05, 2016
  • Author: Marcus Friedrich, MD, MBA, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Overview

Practice Essentials

Pseudomonas aeruginosa has become an important cause of gram-negative infection, especially in patients with compromised host defense mechanisms. It is the most common pathogen isolated from patients who have been hospitalized longer than 1 week, and it is a frequent cause of nosocomial infections. Pseudomonal infections are complicated and can be life-threatening.

Signs and symptoms

Pseudomonal infections can involve the following parts of the body, with corresponding symptoms and signs:

  • Respiratory tract (eg, pneumonia)
  • Bloodstream (bacteremia)
  • Heart ( endocarditis)
  • CNS (eg, meningitis, brain abscess)
  • Ear (eg, otitis externa and media)
  • Eye (eg, bacterial keratitis, endophthalmitis)
  • Bones and joints (eg, osteomyelitis)
  • GI tract (eg, diarrhea, enteritis, enterocolitis)
  • Urinary tract
  • Skin (eg, ecthyma gangrenosum)

Physical findings depend on the site and nature of the infection, as follows:

  • Endocarditis: Fever, murmur, and positive blood culture findings; peripheral stigmata such as Roth spots, Janeway lesions, Osler nodes, splinter hemorrhages, and splenomegaly
  • Pneumonia: Rales, rhonchi, fever, cyanosis, retractions, and hypoxia; occasionally shock; with cystic fibrosis, clubbing, increased anteroposterior (AP) diameter, and malnutrition
  • GI tract: Fever, signs of dehydration, abdominal distention, and signs of peritonitis; physical findings of Shanghai fever
  • Skin and soft tissue infections: Hemorrhagic and necrotic lesions, with surrounding erythema; subcutaneous nodules, deep abscesses, cellulitis, and fasciitis; in burns, black or violaceous discoloration or eschar
  • Skeletal infections: Local tenderness and a decreased range of motion; neurologic deficits
  • Eye infections: Lid edema, conjunctival erythema and chemosis, and severe mucopurulent discharge
  • Malignant otitis externa: Erythematous, swollen, and inflamed external auditory canal; local lymphadenopathy
  • Bacteremia: Fever, tachypnea, and tachycardia; hypotension and shock; jaundice

See Clinical Presentation for more detail.

Diagnosis

Laboratory studies that may be helpful include the following:

  • Complete blood count (CBC)
  • Blood cultures
  • In urinary tract infection (UTI), urinalysis
  • In pneumonia, culture of sputum and respiratory secretions, as well as blood gas analysis
  • Wound and burn cultures and cultures from other body fluids and secretions according to the clinical scenario
  • Gram stain and culture of CSF if meningitis is suspected

Imaging studies that may be warranted include the following:

  • Chest radiography
  • Triple-phase bone scanning in suspected skeletal infection (though many prefer MRI)
  • Brain CT or MRI of the brain for suspected pseudomonal brain abscess
  • Renal ultrasonography for suspected of perinephric abscess complicating UTI
  • Echocardiography for suspected endocarditis with positive blood culture findings

Other tests and procedures that may be helpful in specific scenarios include the following:

  • Fluorescein staining and slit-lamp examination of the cornea for keratitis
  • Flexible fiberoptic bronchoscopy with bronchoalveolar lavage or bronchial brushing
  • Thoracocentesis
  • Lumbar puncture with cell count and cultures

See Workup for more detail.

Management

Antimicrobials are the mainstay of therapy. It is important to consider antibiotic resistance when selecting the regimen. Combination therapy should be used in severe infection. Recommended pharmacologic approaches to specific infections are as follows:

  • Endocarditis: Give a high-dose aminoglycoside plus an extended-spectrum penicillin or antipseudomonal cephalosporin for 6 weeks; surgical evaluation is required
  • Pneumonia: Start with 2 antipseudomonal antibiotics, then deescalating to monotherapy (eg, according to American Thoracic Society-Infectious Diseases Society of America guidelines)
  • Bacteremia: Initiate intravenous antipseudomonal antibiotic therapy before a specific diagnosis is made; subsequent presumptive therapy includes an aminoglycoside plus a broad-spectrum antipseudomonal penicillin or cephalosporin; alternatives include fluoroquinolones and rifampin. In the setting of neutropenia, which carries a high mortality rate, two intravenous antipseudomonal antibiotics from different classes should be used.
  • Meningitis: Ceftazidime is the antibiotic of choice; initial therapy in the critically ill should include an IV aminoglycoside; therapy is ordinarily continued for 2 weeks
  • Ear infections: Treat external otitis with antibiotics and steroids; treat malignant otitis aggressively with 2 antibiotics (and surgery)
  • Eye infections: Treat small superficial ulcers with topical therapy (eg, ophthalmic aminoglycoside solution rather than an ointment) every 30-60 minutes; when perforation is imminent, subconjunctival (or subtenon) administration is preferred; management of endophthalmitis requires aggressive antibiotic therapy (parenteral, topical, subconjunctival [or subtenon], and, often, intraocular)
  • UTIs: Parenteral aminoglycosides are generally preferred, though quinolones are used; monotherapy is appropriate in most cases; alternatives include antipseudomonal penicillins and cephalosporins, carbapenems, and aztreonam; ciprofloxacin is the preferred oral agent
  • GI tract infections: Treatment includes antibiotics and hydration
  • Skin and soft tissue infections: Give double-antibiotic therapy in accordance with local susceptibility pattern. 

 Surgical debridement should be aggressive. Principles of surgical care are as follows:

  • As a rule, infected medical devices should be removed, although exceptions may occur
  • In wounds infected with Pseudomonas, surgical removal of eschars, debridement of necrotic tissue, or, in severe cases, amputation may be required
  • Diabetic foot ulcers may require surgical debridement of necrotic tissue
  • Malignant otitis requires surgery to debride granulation tissue and necrotic debris
  • Surgery may be required for bowel necrosis, perforation, obstruction, or abscess drainage

See Treatment and Medication for more detail.

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Background

Pseudomonas is a gram-negative rod that belongs to the family Pseudomonadaceae. More than half of all clinical isolates produce the blue-green pigment pyocyanin. Pseudomonas often has a characteristic sweet odor.

These pathogens are widespread in nature, inhabiting soil, water, plants, and animals (including humans). Pseudomonas aeruginosa has become an important cause of infection, especially in patients with compromised host defense mechanisms. It is the most common pathogen isolated from patients who have been hospitalized longer than 1 week. It is a frequent cause of nosocomial infections such as pneumonia, urinary tract infections (UTIs), and bacteremia. Pseudomonal infections are complicated and can be life threatening.

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Pathophysiology

P aeruginosa is an opportunistic pathogen. It rarely causes disease in healthy persons. In most cases of infection, the integrity of a physical barrier to infection (eg, skin, mucous membrane) is lost or an underlying immune deficiency (eg, neutropenia, immunosuppression) is present. Adding to its pathogenicity, this bacterium has minimal nutritional requirements and can tolerate a wide variety of physical conditions.

The pathogenesis of pseudomonal infections is multifactorial and complex. Pseudomonas species are both invasive and toxigenic. The 3 stages, according to Pollack (2000), are (1) bacterial attachment and colonization, (2) local infection, and (3) bloodstream dissemination and systemic disease. [1] The importance of colonization and adherence is most evident when studied in the context of respiratory tract infection in patients with cystic fibrosis and in those that complicate mechanical ventilation. Production of extracellular proteases adds to the organism's virulence by assisting in bacterial adherence and invasion.

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Frequency

United States

According to the Centers for Disease Control and Prevention (CDC), an estimated 51,000 healthcare associated P aeruginosa infections in US hospitals  occur each year. More than 6,000 (13%) of these are multidrug-resistant, with about 440 deaths per year. [2, 3] Multidrug-resistant P aeruginosa was given a threat level serious by the CDC.

International

P aeruginosa is common in immunocompromised patients with diabetes.

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Mortality/Morbidity

All infections caused by P aeruginosa are treatable and potentially curable. Acute fulminant infections, such as bacteremic pneumonia, sepsis, burn wound infections, and meningitis, are associated with extremely high mortality rates.

In patients with Charcot arthropathy of the foot, infections with P aeruginosa are associated with a greater number of surgical procedures (1.71 vs 1.28) and longer hospital stays (52 vs 35 days) than infections with methicillin-resistant Staphylococcus aureus (MRSA) or other bacteria, according to a study of 205 patients who underwent surgery for Charcot arthropathy of the feet. The authors propose an algorithm for isolation and surgical and pharmacologic treatment of P aeruginosa infections in this setting, similar to one for MRSA. [4]

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Race

P aeruginosa endocarditis in individuals who abuse intravenous drugs is observed mainly among young black males.

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Sex

Cases of endocarditis and vertebral osteomyelitis have been observed in young males who use intravenous drugs.

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Age

Vertebral osteomyelitis due to pseudomonal infection mainly occurs in elderly patients and often involves the lumbosacral spine. Young people who use intravenous drugs may also be affected.

Involvement of the GI tract most commonly occurs in infants and patients with hematologic malignancies and neutropenia that has resulted from chemotherapy.

The incidence of pseudomonal pneumonia in patients with cystic fibrosis has shown a shift towards patients who are older than 26 years.

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Epidemiology

P aeruginosa is the second most common cause of nosocomial pneumonia (17%), third most common cause of urinary tract infection (7%), fourth most common cause of surgical-site infection (8%), and fifth most common isolate (9%) overall from all sites. [5]  

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