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Original site: www.cdc.gov/legionella/php/laboratories/index.html | RestoredCDC.org is an independent project, not affiliated with CDC or any federal entity. Visit CDC.gov for free official information. Due to archival on January 6, 2025, recent outbreak data is unavailable. Videos are not restored. Access data.restoredcdc.org for restored data. Use of this site implies acceptance of this disclaimer.[More]About Us Report Bug Compare ContentSkip directly to site content Skip directly to search Skip directly to On This PageAn official website of the United States governmentHere's how you knowOfficial websites use .govA .gov website belongs to an official government organization in the United States.Secure .gov websites use HTTPSA lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.Legionella (Legionnaires' Disease and Pontiac Fever)Explore TopicsSearchSearchClear InputFor Everyone* About Legionnaires' Disease* How It Spreads* Health Disparities* Communication Resources* View allHealth Care Providers* Clinical Overview* Clinical Guidance* Clinical Features* View allPublic Health* Lab Testing* Surveillance and Trends* View allRelated Topics:Controlling Legionella | Investigating Legionella CasesView Allsearch close searchsearchLegionella Menu CloseLegionella MenusearchFor Everyone* About Legionnaires' Disease* How It Spreads* Health Disparities* Communication Resources* View All HomeHealth Care Providers* Clinical Overview* Clinical Guidance* Clinical Features* View AllPublic Health* Lab Testing* Surveillance and Trends* View AllRelated Topics* Controlling Legionella* Investigating Legionella CasesView All LegionellaLab Testing Surveillance and Trends View AllJanuary 29, 2024Laboratory Testing for LegionellaKey points* Clinical laboratories can provide diagnostic testing for Legionella infections using culture, serology, or molecular methods.* CDC recommends culture and Legionella urinary antigen testing (UAT) together for diagnosis of Legionnaires' disease.Preferred methodsThe preferred diagnostic tests for Legionnaires' disease are both of the following paired together:* Culture of lower respiratory secretions* Legionella UATLower respiratory secretions include sputum and bronchoalveolar lavage.Importance of cultureCulturing specimens is important to enable detection of all species and serogroups of Legionella. Culturing can detect Legionella species and serogroups that the UAT doesn't as it only detects L. pneumophila serogroup 1.Culture also allows for comparison of clinical and environmental isolates during an outbreak investigation.Keep Reading: Investigation Guidance: Legionella Testing and Specimen CollectionBenefits of the urinary antigen testThe UAT is the most commonly used laboratory test for diagnosis of Legionnaires’ disease. It detects a molecule of the Legionella bacterium in urine. It can detect Legionella in some cases for days to weeks (or longer, under rare circumstances) after treatment.Lab methodsSensitivity and specificitySensitivity varies depending on the following:* Quality and timing of clinical specimen collection* Technical skill of the laboratory worker performing the testThis table provides general ranges for the sensitivity and specificity of each diagnostic test.Test Sensitivity (%) Specificity (%)Culture 20–80 100Urinary antigen for L. pneumophila serogroup 1A (Lp1) 70–100 95–100Polymerase Chain Reaction (PCR)B 95–99 >99Direct Fluorescent Antibody (DFA) Stain 25–75 >95Paired serologyC 80–90 >99Advantages and disadvantagesThis table describes other advantages and disadvantages for each diagnostic test.Test Advantages Disadvantages* Technically difficult* Detects all species and serogroups * Slow (>5 days to grow)Culture * Clinical and environmental isolates can be compared * Sensitivity highly dependent on technical skill* Confirmatory laboratory evidence * Affected by appropriate antibiotic treatment* Requires BCYE agar, which some laboratories may not have readily availableUrinary Antigen * Rapid (same day) * Can only be used to detect L. pneumophila serogroup 1A (Lp1) (which may account for up to 84%D of cases)* Confirmatory laboratory evidence * Does not allow for molecular comparison to environmental isolates* Can be performed on pathologic specimens (usually lung tissue)Nucleic Acid Amplification Test * Rapid * Assays vary by laboratoryE and commercial availability may be limited in the United StatesF* Possible to detect species and serogroups other than Lp1* Confirmatory laboratory evidence* Can be performed on pathologic specimens (usually lung tissue) * Technically difficultDFA * Possible to detect species and serogroups other than Lp1 * Reagents may be difficult to obtain* Supportive laboratory evidenceSerology * Possible to detect species and serogroups other than Lp1 * Must have paired sera collected at acute onset to 2 weeks after symptoms and 3 to 6 weeks laterC,G* Confirmatory laboratory evidence for Lp1; supportive for other types of Legionella * Approximately 5 to 10% of the population has titer 1:≥256 (single acute phase antibody titers of 1:≥256 do not discriminate between cases of Legionnaires’ disease and other causes of community-acquired pneumonia)Specimen collectionBest practice is to obtain both lower respiratory culture and urine concurrently.It's ideal to obtain the lower respiratory culture prior to antibiotic administration. However, antibiotic treatment shouldn't be delayed to facilitate this process. Culture can be attempted even after antibiotic therapy has been initiated.Submitting specimensPublic health department laboratory staff can forward approved specimens to CDC for specialized testing.Keep Reading: Specimen Collection and SubmissionBacteria detectionIncorrect rejection criteriaLaboratories sometimes reject lower respiratory specimens during a work-up for pneumonia based on specimen quality. Issues can include a lack of white blood cells in the sample or contamination with other bacteria.However, laboratories shouldn't reject lower respiratory specimens for these reasons when working-up Legionnaires' disease because Legionella can often be recovered. Sputum produced by patients with Legionnaires' disease may not have many white blood cells1. Contaminating bacteria don't negatively impact isolation of Legionella on selective media (e.g., Buffered Charcoal Yeast Extract [BCYE] agar plus antibiotics)2.ResourcesEnvironmental Legionella Isolation Techniques Evaluation ProgramLaboratories are able to test their proficiency at isolating Legionella from simulated environmental samples. This program issues documentation to those who pass the proficiency test.Legionella Reference Center quick reference guideThis reference center accepts testing requests from governmental public health or environmental laboratories. It performs Legionella testing on clinical specimens and isolates, as well as environmental isolates and outbreak samples.On This Page* Preferred methods* Lab methods* Specimen collection* Submitting specimens* Bacteria detection* ResourcesRelated PagesSpecimen SubmissionRelated Pages** View AllBack to Top* Specimen Submission* Surveillance and TrendsView All LegionellaSpecimen SubmissionJanuary 29, 2024Sources Print ShareFacebook LinkedIn Twitter SyndicateContent Source:National Center for Immunization and Respiratory Diseases; National Center for Environmental HealthFootnotes1. Cross reactions with other species and serogroups have been documented.2. Avni T, Bieber A, Green H, et al. Diagnostic accuracy of PCR alone and compared to urinary antigen testing for detection of Legionella spp.: A systematic review. J Clin Micro. 2016;54(2):401–11.3. CDC labs don't perform serologic testing for legionellosis diagnosis due to inherent challenges in obtaining appropriate specimens. It's important to note that because paired sera are required, results are delayed and thus may not be useful for acute case diagnosis or during active outbreak investigations.4. Yu V, Plouffe JF, Pastoris MC, et al. Distribution of Legionella species and serogroups isolated by culture in patients with sporadic community-acquired legionellosis: An international collaborative survey. J Infect Dis. 2002;186:127–8.5. Laboratories can develop, adopt, or use existing assays (known as laboratory developed tests) for in vitro diagnostic purposes. Labs do this by establishing and validating test performance under the Clinical Laboratory Improvement Amendments of 1988 (CLIA) requirements or equivalent regulations.6. Currently the U.S. Food and Drug Administration has cleared at least one nucleic acid-based molecular assay for Legionella pneumophila detection.7. McDade JE, Shepard CC, Fraser DW, Tsai TR, Redus MA, Dowdle WR. Legionnaires' disease: Isolation of a bacterium and demonstration of its role in other respiratory disease. N Engl J Med. 1977;297(22):1197–203.References1. Murdoch DR. Diagnosis of Legionella infection. Clin Infect Dis. 2003;36:64–9.2. Mercante JW, Winchell JM. Current and emerging Legionella diagnostics for laboratory and outbreak investigations. Clin Microbiol Rev. 2015;28:80–118.Related PagesSpecimen SubmissionRelated Pages** View All* Specimen Submission* Surveillance and TrendsView All LegionellaBack to TopLegionellaLegionella bacteria can cause a severe type of pneumonia (Legionnaires' disease) and mild flu-like illness (Pontiac fever).View AllFor Everyone* About Legionnaires' Disease* How It Spreads* Health Disparities* Communication ResourcesHealth Care Providers* Clinical Overview* Clinical Guidance* Clinical FeaturesPublic Health* Lab Testing* Surveillance and TrendsSign up for Email UpdatesContact UsContact Us* Call 800-232-4636* Contact CDCAbout CDCAbout CDC* Pressroom* Organization* Budget & Funding* Careers & JobsPolicies* Accessibility* External Links* Privacy* Web Policies* FOIA* OIG* No Fear Act* Nondiscrimination* Vulnerability Disclosure PolicyLanguagesLanguages* EspañolLanguage Assistance* Español* 繁體中文* Tiếng Việt* 한국어* Tagalog* Русский* العربية* Kreyòl Ayisyen* Français* Polski* Português* Italiano* Deutsch* 日本語* فارسی* EnglishArchive* CDC Archive* Public Health PublicationsContact UsContact Us* Call 800-232-4636* Contact CDCAbout CDC* Pressroom* Organization* Budget & Funding* Careers & Jobs* About CDCPolicies* Accessibility* External Links* Privacy* Web Policies* FOIA* OIG* No Fear Act* Nondiscrimination* Vulnerability Disclosure PolicyLanguagesLanguages* EspañolLanguage Assistance* Español* 繁體中文* Tiếng Việt* 한국어* Tagalog* Русский* العربية* Kreyòl Ayisyen* Français* Polski* Português* Italiano* Deutsch* 日本語* فارسی* EnglishArchive* CDC Archive* Public Health PublicationsHHS.gov USA.gov
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