Multiple cross displacement amplification-a more applicable technique in detecting Pseudomonas aeruginosa of ventilator-associated pneumonia (VAP).

Background: Early and rapid identification of Pseudomonas aeruginosa (P. aeruginosa) in patients with suspected ventilator-associated pneumonia (VAP) provides theoretical clinical advantages in therapeutic optimization strategies.

Methods: The P. aeruginosa-multiple cross displacement amplification (PA-MCDA) assay was conducted at an isothermal temperature during the amplification stage, and products were visually detected by color changes. The entire process was completed within 1 h. A total of 77 strains, including P. aeruginosa species and various other species of non-P. aeruginosa, were used to evaluate PA-MCDA assays. Bronchoalveolar lavage fluid (BALF) of suspected VAP patients was examined by the MCDA assay.

Results: The MCDA assay exhibited a 100% analytical specificity in detecting PA from all 77 strains, and the limit of detection was as low as 100 fg DNA per reaction. A temperature of 65 °C was recommended as standard during the amplification stage. The agreement between PA-MCDA and bacteria culture was 91.18% (κ = 0.787; p = 0.000) in the identification of P. aeruginosa in BALF from suspected VAP. The PA-MCDA assay showed values of 92.31%, 90.78%, 77.41%, and 97.18% for sensitivity, specificity, positive predictive value, and negative predictive value, respectively. PA-MCDA had a higher detective rate of P. aeruginosa than bacteria culture in patients with antipseudomonal therapy.

Conclusions: The instrument-free platform of the MCDA assay makes it a simple, rapid, and applicable procedure for "on-site" diagnosis and point-of-care testing for the presence of P. aeruginosa without the need for specific bacterial culture.