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 [1] :
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Respiratory tract (eg, pneumonia)
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Bloodstream (bacteremia)
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Heart (endocarditis)
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CNS (eg, meningitis, brain abscess)
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Ear (eg, otitis externa and media) [1]
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Eye (eg, bacterial keratitis, endophthalmitis)
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Bones and joints (eg, osteomyelitis)
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GI tract (eg, diarrhea, enteritis, enterocolitis)
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Urinary tract
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Skin (eg, ecthyma gangrenosum)
Physical findings depend on the site and nature of the infection, as follows [1] :
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Endocarditis: Fever, murmur, and positive blood culture findings; peripheral stigmata such as Roth spots, Janeway lesions, Osler nodes, splinter hemorrhages, and splenomegaly
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Pneumonia: Rales, rhonchi, fever, cyanosis, retractions, and hypoxia; occasionally shock; with cystic fibrosis, clubbing, increased anteroposterior (AP) diameter, and malnutrition
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GI tract: Fever, signs of dehydration, abdominal distention, and signs of peritonitis; physical findings of Shanghai fever
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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
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Skeletal infections: Local tenderness and a decreased range of
Background
Pseudomonas is a gram-negative rod that belongs to the family Pseudomonadaceae. Pseudomonas infections were described in the literature in the 1800s when physicians began to report a condition causing a blue-green discoloration on bandages and associated with a "peculiar" odor. Fordos extracted the blue crystalline pigment in 1869 and called it pyocyanin. [3] In 1894, Williams provided one of the first reviews of case reports of Bacillus pyocyaneus infections. Subsequently, more case reports followed.
In the 1940s, Haynes provided detailed microbiologic characteristics of P aeruginosa that would distinguish it from P fluorescens. By the mid-1990s, P aeruginosa became a great concern as a pathogen associated with burn infections and war-related wounds. During the Vietnam War, P aeruginosa was recorded as one of the three most common wound pathogens. [4, 5]
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, UTIs, and bacteremia. Pseudomonal infections are complicated and can be life threatening.
Pathophysiology
Pseudomonas 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 three stages, according to Pollack (2000), are bacterial attachment and colonization, local infection, and bloodstream dissemination and systemic disease. [6] 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.
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. [7, 8] Multidrug-resistant P aeruginosa was given a threat level serious by the CDC.
International
The rise in antimicrobial resistance (AMR) continues to be a global crisis. [2] Collectively, antimicrobial-resistant pathogens caused more than 2.8 million infections and over 35,000 deaths annually from 2012 through 2017. [7]
Mortality/Morbidity
All infections caused by P aeruginosa are treatable and potentially curable. However drug resistance is a growing concern.29 In 2017, multidrug-resistant P aeruginosa caused an estimated 32,600 infections among hospitalized patients and 2,700 estimated deaths in the United States6. 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. [9]
Race
Pseudomonas aeruginosa endocarditis in individuals who abuse intravenous drugs is observed mainly among young black males.
Sex
Cases of endocarditis and vertebral osteomyelitis have been observed in young males who use intravenous drugs.
Age
Vertebral osteomyelitis due to pseudomonal infection mainly occurs in elderly patients and often involves the lumbosacral spine. Young people who use intravenous drugs also may 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.
Epidemiology
Pseumomonas aeruginosa is the second most common cause of nosocomial pneumonia (17%), third most common cause of UTI (7%), fourth most common cause of surgical-site infection (8%), and fifth most common isolate (9%) overall from all sites. [10]
Pseudomonas is a ubiquitous bacteria commonly found in hospital environments, particularly in moist areas such as sinks and antiseptic solutions. Among the various species, P aeruginosa is a significant pathogen in human infections, with other species like P paucimobilis and P putida also capable of causing disease. In healthcare settings, Pseudomonas infections are a concern, with P aeruginosa being a common cause of nosocomial pneumonia, UTIs, and surgical-site infections. Transmission of Pseudomonas to patients can occur through healthcare workers, particularly in high-risk units such as burn and neonatal intensive care units, emphasizing the importance of strict infection control practices to prevent spread. [1]
Prognosis
Pseudomonas causes a wide spectrum of diseases; therefore, prognosis is varied.
Prognosis of malignant otitis is improving with earlier recognition of the disease and appropriate antibiotic therapy.
Pseudomonal bacteremia, septicemia, meningitis, burn wound sepsis, and eye infections carry a grave prognosis.
Patient Education
Patients should be educated about good hygiene in the care of their ears.
Patients should be educated about the potential adverse effects of medications and should be monitored for the same.
