Test Catalog

Test ID: LEGI    
Legionella Culture, Varies

Useful For Suggests clinical disorders or settings where the test may be helpful

Diagnosis of Legionnaires disease

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

When this test is ordered, the reflex tests may be performed and charged.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

The Legionellaceae are ubiquitous in natural freshwater habitats, allowing them to colonize man-made water supplies, which may then serve as the source for human infections.


Legionella pneumophila and the related species, Legionella bozemanii, Legionella dumoffii, Legionella gormanii, Legionella micdadei, Legionella longbeachae, and Legionella jordanis have been isolated from patients with pneumonia (Legionnaires disease). The organism has been isolated from lung tissue, bronchoalveolar lavage, pleural fluid, and sputum. The signs, symptoms, and radiographic findings of Legionnaires disease are generally nonspecific.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

No growth


Identification of Legionella species.

Interpretation Provides information to assist in interpretation of the test results

Identification of Legionella species from respiratory specimens provides a definitive diagnosis of Legionnaires disease.


Organisms isolated are identified as Legionella species via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and/or 16S rRNA gene sequencing.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Although a semi-selective media is utilized, recovery of Legionella in specimens heavily contaminated with indigenous flora (ie, sputum) may be difficult.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Edelstein PH: Legionella In: Carroll KC, Pfaller MA, eds. Manual of Clinical Microbiology. 12th ed. ASM Press; 2019:905-920

2. Clinical and Laboratory Standards Institute: Interpretive Criteria for Identification of Bacteria and Fungi by Targeted DNA Sequencing. 2nd ed. CLSI Guideline MM18. CLSI; 2018

3. Rucinski SL, Murphy MP, Kies KD, Cunningham SA, Schuetz AN, Patel R: Eight years of clinical Legionella PCR testing illustrates a seasonal pattern. J Infect Dis. 2018 Jul 13;218(4):669-670. doi: 10.1093/infdis/jiy201