A delay in treatment significantly increases the risk of mortality in Legionnaires disease (LD). Therefore, include empiric anti-Legionella therapy in the regimen for severe community-acquired pneumonia (CAP) and in specific cases of nosocomial pneumonia.
Although Legionella pneumonia can present as a mild illness, most patients require hospitalization with parenteral antibiotics. Most healthy hosts exhibit clinical response to treatment within 3-5 days.
Prehospital and Emergency Department Care
Oxygen therapy is the mainstay of prehospital therapy in LD. Intravenous (IV) access and fluid therapy may be indicated for dehydration or septic shock. Restraints may be required for patients with altered mental status. Seizure precautions may be indicated.
Differentiating LD with multiple rigors and altered mental status from a seizure disorder may be possible only through a clinical examination.
Emergency department care
Patient management includes the following:
Control the airway as indicated clinically; support ventilation and oxygenation
Rehydrate the patient as indicated, especially in shock or diarrheal disease
Antipyretics may be used as indicated
Cardiac monitoring may be required if chest pain, hypotension, bradycardia, or other indicators are present
Obtain laboratory specimens (respiratory culture and urine antigen testing), chest radiographs, computed tomography (CT) scans, and cerebrospinal fluid (CSF), as indicated
Begin empiric antibiotic therapy
Also see the Legionella home page from the Centers for Disease Control and Prevention (CDC), as well as the Infectious Diseases Society of America/American Thoracic Society Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults. 
Patients with mild to moderate pneumonia are admitted to the hospital for parenteral antibiotics and supportive measures. Patients deemed to have a severe pneumonia may require admission to the intensive care unit (ICU) for closer monitoring. Quickly initiate empiric antibiotic treatment and obtain a diagnostic workup.
Close follow-up with a pulmonologist or infectious disease specialist is recommended following discharge.
In milder cases, patients can be treated in an outpatient setting with oral antibiotics. For patients who are hospitalized and treated with IV antibiotics, start oral antibiotics while in the hospital and observe the patients for continued response. Continue oral antibiotics on an outpatient basis for 14-21 days, depending on the severity of the presenting illness. Patients should receive close follow-up care to ensure complete resolution of their respiratory symptoms.
Patients should complete the full course of antibiotics, whether the treatment is initiated in the outpatient setting or in the hospital.
Historically, erythromycin, one of the original macrolide antibiotics, was used for L pneumophila infection. Currently, however, other antibiotics, including doxycycline, tigecycline, azithromycin, and a respiratory quinolone, are preferred, because they are more active against LD activity and have superior pharmacokinetic properties (eg, better bioavailability, better penetration into macrophages, longer half-life).
For severe disease, a fluoroquinolone is recommended. With doxycycline or fluoroquinolones, rifampin does not need to be added in severely ill patients.
Consultation with a pulmonologist or infectious disease specialist is strongly recommended in cases of LD. Because of the protean presentation of this disease, however, consultations with other specialists, including the following, may be required at one time or another:
Critical care specialist
Deterrence and Prevention
Prevention and control of nosocomial legionellosis
Legionellae should be sought in hospitalized patients with an increased risk for infection and subsequent death. If 1 definite case or 2 possible cases of nosocomial LD occur among in patients, initiate an investigation for a hospital source.
Legionellae transmission can also be discouraged through the routine maintenance of cooling towers and the use of only sterile water for filling and rinsing nebulization devices. Improved design and maintenance of cooling towers and plumbing systems can also help.
Superheating water to 70-80°C, with flushing of distal sites, may help to prevent water contamination.
Copper-silver ionization units—which produce metallic ions that disrupt the bacterial cell wall, thus resulting in lysis and cell death—are very effective at eradicating legionellae; they provide sustained protection.
Ultraviolet light kills legionellae by damaging cellular deoxyribonucleic acid (DNA). This modality is effective when disinfecting localized areas, but because it provides no sustained protection, adjunctive treatments must be used.
Hyperchlorination of water is no longer recommended, because legionellae are fairly chlorine resistant, and chlorine decomposes at the higher temperatures found in the hot water systems it is used to treat.
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