Page 49 - FoodFocusThailand No.232 July 2025

STRONG QC & QA

From Laboratory to the Field: Table 1 Comparison of RT-PCR and Traditional Culture Methods
Testing for Legionella Comparison Criteria Traditional Culture RT-PCR
The traditional method for detecting Legionella involves Method
culturing water samples on selective media, as specified Time to Results 7–10 days 3–4 hours
in ISO 11731:2017. While this method is highly specific, Sensitivity Moderate High
it has limitations: it requires 7–10 days to obtain results Specificity High High
and may fail to detect bacteria in a viable but non- VBNC Detection Not possible Yes
culturable (VBNC) state. Standard Compliance ISO 11731 ISO/TS 12869,
Real-time polymerase chain reaction (RT-PCR) EN 100030
has emerged in recent years as a powerful
alternative, offering high sensitivity, specificity, and in water systems. As food safety standards continue to rise,
rapid turnaround times. This technology is gaining adopting modern diagnostic methods, such as RT-PCR, is
traction in food processing facilities that require timely essential for maintaining sustainable and safe production
and reliable microbiological monitoring of their water environments.
systems.

RT-PCR: More Information Service Info C008
Fast, Accurate Detection of Legionella DNA
RT-PCR works by amplifying target DNA sequences of เอกสารอ้างอิง / References
1. ISO 11731:2017 – Water quality — Enumeration of Legionella.
Legionella and detecting them via fluorescence signals 2. ISO/TS 12869:2012 – Water quality — Detection and quantification
in real-time. The method provides conclusive results of Legionella spp. and Legionella pneumophila by concentration and
within just 3–4 hours—a significant improvement over quantitative PCR.
3. European Centre for Disease Prevention and Control (ECDC).
culture-based testing. Legionnaires’ disease – Annual epidemiological report.
Key benefits of RT-PCR include: 4. Bartram, J. et al. (2007). Legionella and the prevention of
legionellosis. World Health Organization.
• High Sensitivity: Detect as few as 10 CFU/mL of 5. Collins, S., et al. (2017). “Real-time PCR detection of Legionella
Legionella. spp. in water samples.” Journal of Applied Microbiology, 122(5),

• Excellent Specificity: Utilizes species-specific 1295–1303.

primers and probes specifically designed for Legionella
Legionella spp. or L. pneumophila.
• VBNC Detection: Identifies bacteria that cannot
grow on culture media but may still pose a health risk.
• Quantitative Capability: Enables risk assessment
and trend analysis over time.
However, RT-PCR cannot differentiate between live
and dead bacteria. To address this limitation, advanced
protocols such as PMA-PCR are used to suppress DNA
amplification from non-viable cells, providing a more
accurate representation of active contamination.

Adoption in the Food Industry:
Faster Response, Better Safety
While traditional culture methods remain the reference
standard in many regulatory frameworks, the food
industry increasingly favors RT-PCR for its speed and
precision. Rapid results allow factories to implement
corrective actions without delay, preventing production
downtime or potential product recalls. Investing in
RT-PCR capabilities—including instrumentation
and trained personnel—enhances proactive risk
management and strengthens food safety systems.
This not only protects human health but also builds
consumer trust and competitive advantage in the global
market.
RT-PCR has evolved from a laboratory tool into a
practical solution for real-world challenges in the food
industry. Its speed, sensitivity, and specificity make it a
valuable asset for detecting Legionella contamination
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