Determination of Legionella pneumophila in water by enzyme substrate quantification

Objective To establish an enzyme substrate quantification method for the determination of Legionella pneumophila in water.

Methods The spike comparison test was used to determine the sample preservation conditions and test conditions by the enzyme substrate quantification method. The determination result of the water samples before and after spiking were compared between the enzyme substrate quantification method and the traditional culture method to obtain the technical indicators (accuracy, precision, specificity, and sensitivity) of the enzyme substrate quantification method to determine its detection performance.

Results For the enzyme substrate quantification method, the samples should be sent to the laboratory for testing under normal temperature in sterile sampling containers containing sodium thiosulfate, and the optimum culture condition was 36℃ for 7 days. The accuracy (recovery rate) of this method ranged from 109% to 113%, with a relative standard deviation of 0.37%-2.46% for precision. This method had a specificity of 94.59% and a sensitivity of 92.31%. As for the determination of 50 actual samples, the consistency between the result of the enzyme substrate quantification method and the true values was 94%, and the accuracy and sensitivity of the enzyme substrate quantitative method were higher than those of the traditional culture method.

Conclusion The enzyme substrate quantification method has relatively good accuracy, precision, specificity, and sensitivity and can be used for batch sample screening and determination of low-level Legionella pneumophila contamination. It is a useful supplement to the standard test method of Legionella pneumophila in water and provides a technical reserve for the revision of the national standard method.