The most commonly used laboratory test for diagnosis of Legionnaires’ disease is the urinary antigen test (UAT), which detects a molecule of the Legionella bacterium in urine. If the patient has pneumonia and the test is positive, then you should consider the patient to have Legionnaires’ disease. For More Details about water testing contact: Website: http://www.biosan.com/ Email: info@biosan.com

1. LEGIONELLA LABORATORY TESTING
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2. Indications for Legionnaires’ Disease Testing
• Patients who have failed outpatient antibiotic treatment for
community-acquired pneumonia.
• Patients with severe pneumonia, in particular those requiring
intensive care.
• Immunocompromised patients with pneumonia.
• Patients with a travel history (patients who have traveled away
from their home overnight within 14 days before symptom
onset).
• Hospitalized patients with healthcare-associated pneumonia
(pneumonia with onset ≥48 hours after admission) at risk for
Legionnaires’ disease.
• Patients with an overnight stay in a healthcare facility within 14
days before symptom onset.
• Patients with an epidemiologic link to a setting with a confirmed
source of Legionella or that has been associated with at least one
laboratory-confirmed case of Legionnaires’ disease
Listed below are indications that warrant testing patients with pneumonia for
Legionnaires’ disease:

3. Preferred Diagnostic Tests
Culture
Isolation of Legionella on media that supports growth of
Legionella (i.e., Buffered Charcoal Yeast Extract [BCYE]
agar) is confirmatory and an important method for
diagnosis. Isolation of Legionella can come from lower
respiratory secretions, lung tissue, pleural fluid, or a
normally sterile site. Culturing specimens can detect
Legionella species and serogroups that the urinary antigen
test does not.
UrinaryAntigen Test
The most commonly used laboratory test for diagnosis of
Legionnaires’ disease is the urinary antigen test (UAT), which
detects a molecule of the Legionella bacterium in urine. If the
patient has pneumonia and the test is positive, then you should
consider the patient to have Legionnaires’ disease. The test can
remain positive for a few weeks after infection, even with
antibiotic treatment. The UAT detects the most common cause
of Legionnaires’ disease, L. pneumophila serogroup 1. However,
all species and serogroups of Legionella are potentially
pathogenic, so a patient with a negative urinary antigen result
could have Legionnaires’ disease caused by other Legionella
species or serogroups, which is why using culture and UAT in
combination is recommended.

4. Sensitivity and Specificity of Diagnostic Tests
Sensitivity varies depending on the quality and timing of clinical
specimen collection, as well as technical skill of the laboratory worker
performing the test. The table below provides general ranges for the
sensitivity and specificity of each diagnostic test.
• Culture
• Urinary antigen for L. pneumophila
serogroup1 (Lp1)
• Polymerase Chain Reaction (PCR)2
• Direct Fluorescent Antibody (DFA) Stain
• Paired serology

5. Treatment
If your patient has Legionnaires’ disease, please see the
most recent IDSA-ATS guidelines for treatment of
community-acquired pneumoniaexternal icon and the
most recent IDSA-ATS guidelines for treatment of
hospital-acquired pneumoniaexternal icon. Note that first
line treatment, however, does not always include
Legionella-directed antibiotics (e.g., macrolides and
respiratory fluoroquinolones). While it is preferred that
you obtain diagnostic testing before antibiotic
administration, antibiotic treatment should not be
delayed to facilitate this process.
If your patient has Pontiac fever, antibiotic treatment
should not be prescribed. It is a self-limited illness that
does not benefit from antibiotic treatment. Patients
usually recover within 1 week.

6. Prevention
Minimizing Legionella growth in complex
building water systems and devices is key to
preventing infection. Timely identification
and reporting of legionellosis cases are also
important because this allows public health
officials to act quickly. This way they can
identify and stop potential clusters and
outbreaks by linking new cases to previously
reported ones.

8. Biosan Laboratories is an environmental microbiology laboratory that was
founded by Dr. Harold Rossmoore in 1973. Our initial microbiology lab was in
Ferndale, Michigan where we remained until 1994. Since we knew many of our
lab customers would benefit from the ability to perform microbiology testing
on-site, Biosan developed several bacteria and fungi test kits for industrial
fluids.
About biosan

9. Location
Biosan Laboratories, Inc.
1950 Tobsal Court,
Warren, MI 48091-1351
USA
Contact Us
Call Us
800-253-6800, 586-755-8970

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YOU