Etiology
Legionella pneumophila is an aerobic gram-negative bacillus that flourishes in soil and spreads airborne through cooling towers and air-conditioning systems.
Risk Factors
Middle-aged and elderly people; immunocompromised patients or those with lymphoma or other disorders of delayed hypersensitivity; patients with chronic underlying disease such as diabetes, chronic renal failure, or COPD; people with alcoholism; cigarette smokers; and people on a ventilator for extended periods.
Incubation Period
About 2 to 10 days.
Manifestations
Diarrhea, anorexia, malaise, diffuse myalgias and generalized weakness, headache and recurrent chills, and blood-tinged sputum.
Diagnostic Findings
White blood count shows leukocytosis, chest X-ray shows consolidations, and auscultation reveals fine crackles. Definitive tests include direct immunofluorescence of respiratory tract secretions and tissue, culture of L. pneumophila, and indirect fluorescent antibody testing of serum comparing acute samples with convalescent samples drawn at least 3 weeks later. A convalescent serum showing a fourfold or greater rise in antibody titer for Legionella confirms the diagnosis.
Treatment
Quinolones (ciprofloxacin) and macrolides (erythromycin).
Nursing Management
Closely monitor respiratory status, continually monitor vital signs, replace fluid and electrolytes, provide mechanical ventilation and other respiratory therapy, and give antibiotic therapy as indicated.
Frequently Asked Questions
What is Legionnaires' disease? Legionnaires' disease is a severe pneumonia caused by Legionella bacteria, most often Legionella pneumophila. It hits middle-aged, elderly, and immunocompromised people hardest, and it is one of the more serious causes of community and healthcare associated pneumonia (CDC).
How do people catch it? People get sick by breathing in small droplets of water that contain the bacteria. Legionella grows in building water systems such as cooling towers, hot tubs, large plumbing systems, and decorative fountains. It does not usually spread from person to person (CDC).
How serious is it? It is fatal in about 1 in 10 people who get it. For infections acquired in a healthcare setting, the case fatality rate is higher, around 1 in 4, because those patients tend to be sicker to begin with (CDC).
What are the warning signs a nurse should watch for? Cough, shortness of breath, fever, muscle aches, and headache are typical. Some patients also have diarrhea, confusion, or nausea. Symptoms usually start 2 to 10 days after exposure, so a recent travel, hospital, or water exposure history matters (CDC).
How is it diagnosed? A urinary antigen test and a culture of lower respiratory secretions are the usual frontline tests. Chest imaging confirms pneumonia, and paired acute and convalescent antibody titers can support the diagnosis when a fourfold rise is seen.
Which antibiotics treat it? Legionella needs antibiotics that work inside cells. Current practice favors a respiratory fluoroquinolone such as levofloxacin or a macrolide such as azithromycin over older agents. Treatment should not wait for confirmation when the clinical picture fits (CDC).