Approach Considerations
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
Prehospital 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:
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Control the airway as indicated clinically; support ventilation and oxygenation
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Rehydrate the patient as indicated, especially in shock or diarrheal disease
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Antipyretics may be used as indicated
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Cardiac monitoring may be required if chest pain, hypotension, bradycardia, or other indicators are present
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Obtain laboratory specimens (respiratory culture and urine antigen testing), chest radiographs, computed tomography (CT) scans, and cerebrospinal fluid (CSF), as indicated
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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. [16]
Inpatient Care
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.
Antibiotic Therapy
In milder cases, patients can be treated in an outpatient setting with oral antibiotics that are targeted against legionella and are bacterocidal, have long half-lives and achieve high lung tissue concentrations. First line agents would include levofloxacin (a fluroquinolone) and azithromycin (a macrolide) administered through the oral route. Alternative agents would include other fluroquinolone s such as ciprofloxacin, moxifloxacin, doxycycline (a tetracycline). Other macrolides would include clarithromycin, erythromycin and roxithromycin. Newer tetracyclines such as tigecycline have been used as second line agents against L pneumoniae but appears to have limited activity against L longbeachae and therefore, should be avoided if this strain is suspected. [17]
For patients with L longbeachae infection, a fluroquinolone or a macrolide should be used. Treatment duration can range from 5-10 days in mild cases.
For patients with moderate or severe infection that require hospitalization, or those who cannot tolerate oral medications, the intravenous route of administration is preferred. When patients become clinically stable and can tolerate orally, they can then be transitioned to the oral equivalent. For severe disease, a fluoroquinolone is recommended. Adding rifampin to a regimen of fluroquinolone or macrolide, has not been shown to have any additional benefits. [18] .
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.
Consultations
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:
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General internist
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Critical care specialist
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Cardiologist
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Gastroenterologist
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Neurologist
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Nephrologist
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Oncologist
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General surgeon
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.
Disinfection
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.
Following reports of LD in newborns who were infected during water births, [5] the Arizona Department of Health Services issues recommendation for minimizing the risk of Legionella contamination in tubs used during the water birthing process, such as flushing out stagnant water and sediment from hoses by running hot water through it for 3 minutes before using it to fill the tub. [19]
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This electron micrograph depicts an amoeba, Hartmannella vermiformis (orange), as it entraps a Legionella pneumophila bacterium (green) with an extended pseudopod. After it is ingested, the bacterium can survive as a symbiont within what then becomes its protozoan host. The amoeba then becomes a so-called "Trojan horse," since, by harboring the pathogenic bacterium, the amoeba can afford it protection. In fact, in times of adverse environmental conditions, the amoeba can metamorphose into a cystic stage, enabling it, and its symbiotic resident, to withstand the environmental stress. Image courtesy of the Centers for Disease Control and Prevention and Dr. Barry S Fields.
Tables
Diagnostic Predictors |
Diagnostic Eliminators |
Clinical Predictors
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Clinical Eliminators
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Laboratory Predictors b
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Laboratory Eliminators
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Legionnaire disease very likely if >3 predictors present |
Legionnaires disease very unlikely if < 3 predictors or >3 diagnostic eliminators present |
Abbreviations: CPK = creatinine phosphokinase test; CRP = C-reactive protein; ESR = erythrosedimentation rate. a Pulmonary symptoms: shortness of breath, cough, and so forth with fever and a new focal/segmental infiltrate on chest radiograph. b Otherwise unexplained. If finding is due to an existing disorder, it should not be used as a clinical predictor. |
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