Objective: To compare the detection effect of Legionella pollution in spring water by three methods, namely traditional plating method, fluorescent quantitation PCR method and ethidium monoazide (EMA) fluorescent quantitation PCR method.
Methods: Every month (except May), we collected 11 water samples from the 5 selected hot spring pools in one hot spring resort in Beijing in 2011. A total of 121 water samples were collected, and then were detected by the above three methods qualitatively and quantitatively.
Results: In our study, the Legionella pollution rate was separately 74.4% (90/121), 100.0% (121/121) and 100.0% (121/121) by the above three methods. The quantitative value of Legionella in the 121 water samples detected by the three methods were around 0.10-216.00 colony-forming units (CFU)/ml, 1.47-1557.75 gene units (GU)/ml and 0.20-301.69 GU/ml, respectively. The median (25th and 75th percentiles) was 75.30 (32.51-192.10) GU/ml, 36.46 (16.08-91.21) GU/ml and 5.30 (0.00-33.70) CFU/ml, respectively. The difference in the quantitative value of Legionella detected by the three methods showed statistical significance (χ(2) = 187.900, P < 0.01). The quantitative value of Legionella detected by fluorescent quantitation PCR method was the highest, followed by the value Legionella detected by EMA-fluorescent quantitation PCR method and traditional plating method.
Conclusion: The sensitivity of the PCR methods was higher than traditional plating method, in detecting Legionella pollution in spring water, especially the EMA- fluorescent quantitation PCR method, which was more suitable for detecting Legionella in water.