Medscape is available in 5 Language Editions – Choose your Edition here.


Pseudomonas aeruginosa Infections

  • Author: Marcus Friedrich, MD, MBA, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
Updated: Dec 17, 2015

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.


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.


Antimicrobials are the mainstay of therapy. It is important to consider antibiotic resistance when selecting the regimen. Commination 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.



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.



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.



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.


P aeruginosa is common in immunocompromised patients with diabetes.



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]



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



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



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.



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]  

Contributor Information and Disclosures

Marcus Friedrich, MD, MBA, FACP Medical Director Office of Quality and Patient Safety, New York State Department of Health; Assistant Professor, Hofstra North Shore-LIJ School of Medicine at Hofstra University

Marcus Friedrich, MD, MBA, FACP is a member of the following medical societies: American Academy of Family Physicians, American College of Physicians, American Medical Association

Disclosure: Nothing to disclose.


Klaus-Dieter Lessnau, MD, FCCP Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital

Klaus-Dieter Lessnau, MD, FCCP is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Medical Association, American Thoracic Society, Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Burke A Cunha, MD Professor of Medicine, State University of New York School of Medicine at Stony Brook; Chief, Infectious Disease Division, Winthrop-University Hospital

Burke A Cunha, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John L Brusch, MD, FACP Assistant Professor of Medicine, Harvard Medical School; Consulting Staff, Department of Medicine and Infectious Disease Service, Cambridge Health Alliance

John L Brusch, MD, FACP is a member of the following medical societies: American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Chief Editor

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American Medical Association, Oklahoma State Medical Association, Southern Society for Clinical Investigation, Association of Professors of Medicine, American College of Physicians, Infectious Diseases Society of America

Disclosure: Nothing to disclose.

Additional Contributors

Pratibha Dua, MD, MBBS Staff Physician, Internal Medicine, United Medical Park

Pratibha Dua, MD, MBBS is a member of the following medical societies: American Medical Association

Disclosure: Nothing to disclose.

Thomas J Marrie, MD Dean of Faculty of Medicine, Dalhousie University Faculty of Medicine, Canada

Thomas J Marrie, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, Association of Medical Microbiology and Infectious Disease Canada, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.


Samer Qarah, MD Pulmonary Critical Care Consultant, Department of Internal Medicine, Division of Pulmonary and Critical Care, The Brooklyn Hospital Center and Cornell University

Samer Qarah, MD is a member of the following medical societies: American College of Critical Care Medicine

Disclosure: Nothing to disclose.

  1. Pollack M. Pseudomonas Aeruginosa. Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 5th ed. New York, NY: Churchill Livingstone; 2000. 2310-27.

  2. CDC. Antibiotic Resistance Threats in the United States, 2013. Centers for Disease Control and Prevention. Available at

  3. Textbook of Bacteriology. Todar's Online Textbook of Bacteriology. [Full Text].

  4. Illgner U, Uekoetter A, Runge S, Wetz HH. Infections with Pseudomonas aeruginosa in Charcot arthropathy of the foot. Foot Ankle Int. 2013 Feb. 34(2):234-7. [Medline].

  5. National Nosocomial Infections Surveillance (NNIS) System. National Nosocomial Infections Surveillance (NNIS) System Report, data summary from January 1992 through June 2004, issued October 2004. Centers for Disease Control and Prevention. Available at

  6. Ratjen F, Munck A, Kho P, Angyalosi G. Treatment of early Pseudomonas aeruginosa infection in patients with cystic fibrosis: the ELITE trial. Thorax. 2010 Apr. 65(4):286-91. [Medline].

  7. Aloush V, Navon-Venezia S, Seigman-Igra Y, Cabili S, Carmeli Y. Multidrug-resistant Pseudomonas aeruginosa: risk factors and clinical impact. Antimicrob Agents Chemother. 2006 Jan. 50 (1):43-8. [Medline].

  8. Bitsori M, Maraki S, Koukouraki S, Galanakis E. Pseudomonas aeruginosa urinary tract infection in children: risk factors and outcomes. J Urol. 2012 Jan. 187(1):260-4. [Medline].

  9. Abuqaddom AI, Darwish RM, Muti H. The effects of some formulation factors used in ophthalmic preparations on thiomersal activity against Pseudomonas aeruginosa and Staphylococcus aureus. J Appl Microbiol. 2003. 95(2):250-5. [Medline].

  10. Bliziotis IA, Samonis G, Vardakas KZ, Chrysanthopoulou S, Falagas ME. Effect of aminoglycoside and beta-lactam combination therapy versus beta-lactam monotherapy on the emergence of antimicrobial resistance: a meta-analysis of randomized, controlled trials. Clin Infect Dis. 2005 Jul 15. 41(2):149-58. [Medline].

  11. Chamot E, Boffi El Amari E, Rohner P, Van Delden C. Effectiveness of combination antimicrobial therapy for Pseudomonas aeruginosa bacteremia. Antimicrob Agents Chemother. 2003 Sep. 47(9):2756-64. [Medline].

  12. Crouch Brewer S, Wunderink RG, Jones CB, Leeper KV Jr. Ventilator-associated pneumonia due to Pseudomonas aeruginosa. Chest. 1996 Apr. 109(4):1019-29. [Medline].

  13. Cunha BA. Clinical relavance of penicillin resistant Streptococcus pneumoniae. Semin Respir Infect. 2002 Sep. 17(3):204-14. [Medline].

  14. Cunha BA. New uses for older antibiotics: nitrofurantoin, amikacin, colistin, polymyxin B, doxycycline, and minocycline revisited. Med Clin North Am. 2006 Nov. 90(6):1089-107. [Medline].

  15. Cunha BA. Ventilator associated pneumonia: monotherapy is optimal if chosen wisely. Crit Care. 2006. 10(2):141. [Medline].

  16. Cunha BA. Multidrug resistant (MDR) Klebsiella, Acinetobacter, and Pseudomonas aeruginosa. Antibiotics for Clinicians. 2006. 10:354-355.

  17. Cunha BA. Pseudomonas aeruginosa: resistance and therapy. Semin Respir Infect. 2002. 17:231-239. [Medline].

  18. Edelstein MV, Skleenova EN, Shevchenko OV, D'souza JW, Tapalski DV, Azizov IS, et al. Spread of extensively resistant VIM-2-positive ST235 Pseudomonas aeruginosa in Belarus, Kazakhstan, and Russia: a longitudinal epidemiological and clinical study. Lancet Infect Dis. 2013 Jul 8. [Medline].

  19. Edgeworth JD, Treacher DF, Eykyn SJ. A 25-year study of nosocomial bacteremia in an adult intensive care unit. Crit Care Med. 1999 Aug. 27(8):1421-8. [Medline].

  20. Fiorillo L, Zucker M, Sawyer D, Lin AN. The pseudomonas hot-foot syndrome. N Engl J Med. 2001 Aug 2. 345(5):335-8. [Medline].

  21. Garcia-Lechuz JM, Cuevas O, Castellares C, Perez-Fernandez C, Cercenado E, Bouza E. Streptococcus pneumoniae skin and soft tissue infections: characterization of causative strains and clinical illness. Eur J Clin Microbiol Infect Dis. 2007 Apr. 26(4):247-53. Epub. [Medline].

  22. Gavin PJ, Suseno MT, Cook FV, Peterson LR, Thomson RB Jr. Left-sided endocarditis caused by Pseudomonas aeruginosa: successful treatment with meropenem and tobramycin. Diagn Microbiol Infect Dis. 2003 Oct. 47(2):427-30. [Medline].

  23. Heal CF, Buettner PG, Cruickshank R, Graham D, Browning S, Pendergast J, et al. Does single application of topical chloramphenicol to high risk sutured wounds reduce incidence of wound infection after minor surgery? Prospective randomised placebo controlled double blind trial. BMJ. 2009 Jan 15. 338:a2812. [Medline]. [Full Text].

  24. Hoban DJ, Zhanel GG. Clinical implications of macrolide resistance in community-acquired respiratory tract infections. Expert Rev Anti Infect Ther. 2006 Dec. 4(6):973-80. [Medline].

  25. Ibrahim EH, Ward S, Sherman G, Kollef MH. A comparative analysis of patients with early-onset vs late-onset nosocomial pneumonia in the ICU setting. Chest. 2000 May. 117(5):1434-42. [Medline].

  26. Janeczko L. Study Finds Rapid Spread of Extensively Drug-Resistant P. aeruginosa. Medscape Medical News. Available at Accessed: August 4, 2013.

  27. Karlowsky JA, Draghi DC, Jones ME, Thornsberry C, Friedland IR, et al. Surveillance for antimicrobial susceptibility among clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii from hospitalized patients in the United States, 1998 to 2001. Antimicrob Agents Chemother. 2003 May. 47(5):1681-8. [Medline].

  28. Klibanov OM, Raasch RH, Rublein JC. Single versus combined antibiotic therapy for gram-negative infections. Ann Pharmacother. 2004 Feb. 38(2):332-7. [Medline].

  29. Micek ST, Lloyd AE, Ritchie DJ, Reichley RM, Fraser VJ, Kollef MH. Pseudomonas aeruginosa bloodstream infection: importance of appropriate initial antimicrobial treatment. Antimicrob Agents Chemother. 2005 Apr. 49(4):1306-11. [Medline].

  30. Muramatsu H, Horii T, Morita M, Hashimoto H, Kanno T, Maekawa M. Effect of basic amino acids on susceptibility to carbapenems in clinical Pseudomonas aeruginosa isolates. Int J Med Microbiol. 2003 Jun. 293(2-3):191-7. [Medline].

  31. Paul M, Silbiger I, Grozinsky S, Soares-Weiser K, Leibovici L. Beta lactam antibiotic monotherapy versus beta lactam-aminoglycoside antibiotic combination therapy for sepsis. Cochrane Database Syst Rev. 2006. (1):CD003344. [Medline].

  32. Quittner AL, Modi AC, Wainwright C, Otto K, Kirihara J, Montgomery AB. Determination of the minimal clinically important difference scores for the Cystic Fibrosis Questionnaire-Revised respiratory symptom scale in two populations of patients with cystic fibrosis and chronic Pseudomonas aeruginosa airway infection. Chest. 2009 Jun. 135(6):1610-8. [Medline]. [Full Text].

  33. Retsch-Bogart GZ, Quittner AL, Gibson RL, Oermann CM, McCoy KS, Montgomery AB, et al. Efficacy and safety of inhaled aztreonam lysine for airway pseudomonas in cystic fibrosis. Chest. 2009 May. 135(5):1223-32. [Medline]. [Full Text].

  34. Schoni MH. Macrolide antibiotic therapy in patients with cystic fibrosis. Swiss Med Wkly. 2003 May 31. 133(21-22):297-301. [Medline].

  35. Shorr AF. Review of studies of the impact on Gram-negative bacterial resistance on outcomes in the intensive care unit. Crit Care Med. 2009 Apr. 37(4):1463-9. [Medline].

  36. van Delden C. Pseudomonas aeruginosa bloodstream infections: how should we treat them?. Int J Antimicrob Agents. 2007 Nov. 30 Suppl 1:S71-5. [Medline].

  37. Veesenmeyer JL, Hauser AR, Lisboa T, Rello J. Pseudomonas aeruginosa virulence and therapy: evolving translational strategies. Crit Care Med. 2009 May. 37(5):1777-86. [Medline]. [Full Text].

  38. Vonberg RP, Gastmeier P. Isolation of infectious cystic fibrosis patients: results of a systematic review. Infect Control Hosp Epidemiol. 2005 Apr. 26(4):401-9. [Medline].

  39. Wang S, Kwok M, McNamara JK, Cunha BA. Colistin for multi-drug resistant (MDR) gram-negative bacillary infections. Antibiotics for Clinicians. 2007. 11:389-396.

All material on this website is protected by copyright, Copyright © 1994-2016 by WebMD LLC. This website also contains material copyrighted by 3rd parties.