Next Day Legionella PCR: a highly reliable negative screen for Legionella in the built environment

• Published in: Journal of water and health Vol. 18; no. 3; pp. 345 - 357
• Main Authors: Fisher, Katherine E, Wickenberg, Leah P, Leonidas, Lesley F, Ranz, Anna A, Habib, Michelle A, Buford, Rafael M, McCoy, William F
• Format: Journal Article
• Language: English
• Published: England IWA Publishing 01.06.2020
• Subjects: Agglutination tests; Approximation; Bacteria; Built Environment; Deoxyribonucleic acid; Disease control; DNA; Drinking water; Humans; Infections; Legionella; Legionella pneumophila; Legionnaire's disease; Legionnaires disease; Medical laboratories; Methods; Nucleotide sequence; Opportunist infection; Pathogens; PCR; Pneumonia; Polymerase chain reaction; Real-Time Polymerase Chain Reaction; Reproducibility of Results; United States; Urban environments; Water analysis; Water mains; Water management; Water Microbiology; Water sampling; United States; United States > US
• ISSN: 1477-8920; 1996-7829
• DOI: 10.2166/wh.2020.004

The opportunistic, waterborne pathogen Legionella caused 9,933 cases of Legionnaires' disease in 2018 in the United States (CDC.gov). The incidence of Legionnaires' disease can be reduced by maintaining clean building water systems through water management programs (WMPs). WMPs often include validation testing to confirm the control of bacteria, but the traditional culture method for enumerating Legionella requires 10-14 days to obtain results. A rapid DNA extraction developed by Phigenics and a real-time PCR negative screen for the genus Legionella provided results the day after sampling. This study evaluated the Next Day Legionella PCR (Phigenics, LLC) compared with the traditional culture method (ISO 11731) on 11,125 building water samples for approximately 1 year. Two DNA extraction methods (Methods 1 and 2) were compared. The negative predictive value (NPV) of the Next Day Legionella PCR in comparison to traditional culture for Method 1 was 99.95%, 99.92%, 99.85%, and 99.17% at >10, >2, >1, and >0.1 CFU/ml limits of detection, respectively. The improved DNA extraction (Method 2) increased the NPV to 100% and 99.88% at >1 and >0.1 CFU/ml, respectively. These results demonstrate the reliability of the genus-level Legionella PCR negative screen to predict culture-negative water samples.