Objective To compare the detection capabilities of the lipopolysaccharide bioprobe method and traditional culture methods (including ISO 11731-2017 and GB/T 18204.5-2013) for quantifying Legionella pneumophila in water.
Methods The lipopolysaccharide bioprobe method and traditional culture methods were applied separately to test 58 spiked water samples (50 spiked actual water samples for method comparison and 8 spiked purified water samples for performance test of the lipopolysaccharide bioprobe method) and 50 actual water samples. The detection limit, accuracy, precision, specificity, and sensitivity of the lipopolysaccharide bioprobe method were determined. The methods were compared for the qualitative results of 50 actual water samples before spiking and the quantitative results of 50 actual water samples before and after spiking.
Results For the lipopolysaccharide bioprobe method, the detection limit was 1.55 CFU/L, the accuracy was 102.10%-139.29%, the precision was 0.14%-1.78%, the specificity was 95.12%, and the sensitivity was 88.89%. There was no significant difference in the qualitative results (detected or undetected) of 50 actual water samples before spiking between the lipopolysaccharide bioprobe method and the GB/T method (P>0.05). For 50 actual water samples before and after spiking, the medians (M) of the quantitative results with the lipopolysaccharide bioprobe method were significantly higher than those with the ISO method (P < 0.001), and the results with the two method were significantly correlated with each other (r=0.981). The detection limit of the lipopolysaccharide bioprobe method (1.55 CFU/L) was lower than that of the ISO method (15.74 CFU/L), and the detection time of the former (2 d) was shorter than that of the latter (10 d).
Conclusion The lipopolysaccharide bioprobe method is a new method for detecting Legionella pneumophila in water, with shorter detection time and better detection performance compared with traditional culture methods.
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