One step for Legionella pneumophila detection in environmental samples by DNA-gold nanoparticle probe.

AIMS: To develop and evaluate a DNA-gold nanoparticle (DNA-AuNP) probe assay to detect Legionella pneumophila, which causes Legionnaires' disease, compared with the gold standard culture method.

METHODS AND

RESULTS

Gold nanoparticles (AuNPs) were conjugated with DNA probes to detect the mip gene of L. pneumophila. The DNA-AuNP probe assay was evaluated for its specificity, sensitivity and stability. The results showed that only L. pneumophila mixed with this probe resulted in a red solution that was easily detected by the naked eye, and the colour was stable when 10 mmol l-1 MgSO4 was added. The 100 Legionella isolates and 10 other bacteria led to 100% specificity. Compared with the culture method, our method showed a 100% negative predictive value, 100% sensitivity (kappa = 0·87), and a detection limit of 4·5 ng DNA μl-1 with a 6-min response time for the 124 colonies suspected of being Legionella. The DNA-AuNP probe reagents were stable for more than 6 months.

CONCLUSIONS

The developed DNA-AuNP probe assay has good negative predictive value, sensitivity, rapidity and ease of use, which is helpful for ruling out negative samples.

SIGNIFICANCE AND IMPACT OF THE STUDY: The DNA-AuNP probe assay can detect the mip gene of L. pneumophila. Therefore, it may be an alternative method for screening colonies suspected of being L. pneumophila.