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.

Ultrasonographic optic nerve sheath diameter correlation with ICP and accuracy as a tool for noninvasive surrogate ICP measurement in patients with decompressive craniotomy.

OBJECTIVE: Increased intracranial pressure (ICP) results in enlarged optic nerve sheath diameter (ONSD). In this study the authors aimed to assess the association of ONSD and ICP in severe traumatic brain injury (TBI) after decompressive craniotomy (DC). METHODS: ONSDs were measured by ocular ultrasonography in 40 healthy control adults. ICPs were monitored invasively with a microsensor at 6 hours and 24 hours after DC operation in 35 TBI patients. ONSDs were measured at the same time in these patients. Patients were assigned to 3 groups according to ICP levels, including normal (ICP ≤ 13 mm Hg), mildly elevated (ICP = 14-22 mm Hg), and severely elevated (ICP > 22 mm Hg) groups. ONSDs were compared between healthy control adults and TBI cases with DC. Then, the association of ONSD with ICP was analyzed using Pearson's correlation coefficient, linear regression analysis, and receiver operator characteristic curves. RESULTS: Seventy ICP measurements were obtained among 35 TBI patients after DC, including 25, 27, and 18 measurements in the normal, mildly elevated, and severely elevated ICP groups, respectively. Mean ONSDs were 4.09 ± 0.38 mm in the control group and 4.92 ± 0.37, 5.77 ± 0.41, and 6.52 ± 0.44 mm in the normal, mildly elevated, and severely elevated ICP groups, respectively (p < 0.001). A significant linear correlation was found between ONSD and ICP (r = 0.771, p < 0.0001). Enlarged ONSD was a robust predictor of elevated ICP. With an ONSD cutoff of 5.48 mm (ICP > 13 mm Hg), sensitivity and specificity were 91.1% and 88.0%, respectively; a cutoff of 5.83 mm (ICP > 22 mm Hg) yielded sensitivity and specificity of 94.4% and 81.0%, respectively. CONCLUSIONS: Ultrasonographic ONSD is strongly correlated with invasive ICP measurements and may serve as a sensitive and noninvasive method for detecting elevated ICP in TBI patients after DC.