Modern qPCR Outperforms Culture Tests for Legionella Detection – In Only One Day

In just one day, viability qPCR detected Legionella in 65.9% of real-world water samples. This was more than four times the 15.4% detection rate of ISO 11731 culture test that took up to 14 days. 

A 2023 study by Q Labs LLC found that viability qPCR is significantly more effective than traditional ISO 11731 culture tests for detecting Legionella in building water systems. Researchers tested 91 real-world water samples using both methods. Culture tests identified Legionella in just 15.4 percent of samples, while qPCR detected it in 65.9 percent.

For all positive culture tests, samples were also qPCR-positive. However, more than half of the samples that were qPCR-positive were found to be culture-negative. This highlights the culture test’s failure to detect low-level or viable-but-non-culturable organisms. Moreover, qPRC had a significant time advantage of just one day versus up to 14 days for the culture test.

qPCR rated 17 of 91 samples as higher risk than culture (8 one level higher, 9 two levels), while culture was stricter just once. The findings suggest that qPCR with viability reagents is a more accurate and timely tool for routine Legionella monitoring and should be considered as a primary method in Water Management Programs.Which type of Legionella test is appropriate for your Legionella testing? Contact the independent Legionella testing experts at Legionella Control Systems. Our team will help you evaluate your situation, facility, Legionella water quality monitoring, and timing needs, and recommend the best testing option that works for your budget.