Louise Krojgaard, of the Department of Microbiological Surveillance and Research, at Statens Serum Institut in Copenhagen, Denmark, and colleagues sought to investigate the usefulness of qPCR compared to culture for monitoring remedial actions for elimination of Legionella bacteria and as a tool for risk assessment.
Culture and quantitative polymerase chain reaction (qPCR) assays for the detection of Legionella were compared on samples from a residential area before and after two interventions. A total of 84 samples were collected from shower hoses and taps as first flush samples and at constant temperature. Samples were grouped according to the origin of the sample, a) circulation water b) water from empty apartments c) water from shower hoses.
In water collected from the apartments Legionella spp were detected by qPCR in the concentration range from LOQ to 9.6*105GU/L while L. pneumophila were detected in a range from LOQ to 6.8 *105 GU/L. By culturing, the legionellae were detected in the range from below detection limit (> 10 CFU/L) to 1.6 * 106 CFU/L. In circulating water and in first flush water from shower hoses, culture and qPCR showed the same tendencies. The overall correlation between the bacteria number detected by culture and the two developed qPCR assays (L. spp and L. pneumophila) was relatively poor (r2 =0.31 for culture and Legionella spp. assay, r2 = 0.20 for culture and L. pneumophila assay).
The researchers concluded that detection by qPCR was suitable for monitoring changes in the concentration of Legionella but the precise determination of bacteria is difficult. Risk assessment by qPCR only on samples without any background information regarding treatment, timing, etc is dubious. However, the rapid detection by qPCR of high concentrations of Legionella - especially Legionella pneumophila - is valuable as an indicator of risk, although it may be false positive compared to culture results. On the other hand, the detection of a low number of bacteria by qPCR is a strong indication for the absence of risk. Their research was published in BMC Microbiology.Â
Reference: Krojgaard LH, Krogfelt KA, Albrechtsen HJ and Uldum SA. Detection of Legionella by quantitative-Polymerase Chain Reaction (qPCR) for monitoring and risk assessment. BMC Microbiology 2011, 11:254doi:10.1186/1471-2180-11-254
I Was There: An Infection Preventionist on the COVID-19 Pandemic
April 30th 2025Deep feelings run strong about the COVID-19 pandemic, and some beautiful art has come out of those emotions. Infection Control Today is proud to share this poem by Carmen Duke, MPH, CIC, in response to a recent article by Heather Stoltzfus, MPH, RN, CIC.
From the Derby to the Decontam Room: Leadership Lessons for Sterile Processing
April 27th 2025Elizabeth (Betty) Casey, MSN, RN, CNOR, CRCST, CHL, is the SVP of Operations and Chief Nursing Officer at Surgical Solutions in Overland, Kansas. This SPD leader reframes preparation, unpredictability, and teamwork by comparing surgical services to the Kentucky Derby to reenergize sterile processing professionals and inspire systemic change.
Show, Tell, Teach: Elevating EVS Training Through Cognitive Science and Performance Coaching
April 25th 2025Training EVS workers for hygiene excellence demands more than manuals—it requires active engagement, motor skills coaching, and teach-back techniques to reduce HAIs and improve patient outcomes.