ABSTRACT
A novel amperometric magnetoimmunoassay, based on the use of core-shell magnetic nanoparticles and screen-printed carbon electrodes, was developed for the selective determination of Legionella pneumophila SG1. A specific capture antibody (Ab) was linked to the poly(dopamine)-modified magnetic nanoparticles (MNPs@pDA-Ab) and incubated with bacteria. The captured bacteria were sandwiched using the antibody labeled with horseradish peroxidase (Ab-HRP), and the resulting MNPs@pDA-Ab-Legionella neumophila-Ab-HRP were captured by a magnetic field on the electrode surface. The amperometric response measured at -0.15 V vs. Ag pseudo-reference electrode of the SPCE after the addition of H2O2 in the presence of hydroquinone (HQ) was used as transduction signal. The achieved limit of detection, without pre-concentration or pre-enrichment steps, was 10(4) Colony Forming Units (CFUs) mL(-1). The method showed a good selectivity and the MNPs@pDA-Ab exhibited a good stability during 30 days. The possibility of detecting L. pneumophila at 10 CFU mL(-1) level in less than 3 h, after performing a membrane-based preconcentration step, was also demonstrated.
Subject(s)
Antibodies, Immobilized/chemistry , Electrochemical Techniques/methods , Immunoassay/methods , Indoles/chemistry , Legionella pneumophila/isolation & purification , Legionnaires' Disease/microbiology , Magnetite Nanoparticles/chemistry , Polymers/chemistry , Biosensing Techniques/methods , Humans , Legionnaires' Disease/diagnosis , Limit of DetectionABSTRACT
RATIONALE: Temperature curve complexity is inversely related to clinical status in critically ill patients. OBJECTIVE: To study if temperature curve complexity analysis predicts clinical outcome and how this test compares to other well-established conventional measures. METHODS: Temperature was continuously recorded in 50 patients with multiple organ failure. Time-series complexity was analyzed using hourly approximate entropy (ApEn) and detrended fluctuation analysis (DFA) values. Sequential Organ Failure Assessment (SOFA) score was obtained every other day, and correlation between complexity and SOFA values was evaluated. Differences in complexity between nonsurviving and surviving patients were likewise analyzed. Logistic regression models were calculated to predict outcome, and receiver operating characteristic (ROC) curves were plotted to compare the predictive power of complexity values versus SOFA. MEASUREMENTS AND RESULTS: There was good correlation between complexity results and clinical scores for each patient. Nonsurvivors exhibited lower complexity values than survivors (minimum ApEn = 0.230 vs. 0.378; maximum DFA = 1.636 vs. 1.507; mean ApEn = 0.459 vs. 0.596; mean DFA = 1.376 vs. 1.288; p < 0.001 for all comparisons). In the logistic regression model, a change of 0.1 in the minimum complexity resulted in severe increases in the odds ratio of dying (7.6-fold for ApEn, 5.4-fold for DFA). In terms of predicting outcome, there were no significant differences in the areas under the ROC curves for complexity values versus SOFA scores. CONCLUSIONS: Low levels of complexity in the temperature curve are indicators of poor prognosis in patients with multiple organ failure. The predictive ability of temperature curve complexity is similar to that of the SOFA score.
Subject(s)
Body Temperature Regulation/physiology , Critical Care/methods , Multiple Organ Failure/physiopathology , Severity of Illness Index , Skin Temperature/physiology , APACHE , Adolescent , Adult , Aged , Aged, 80 and over , Female , Humans , Logistic Models , Male , Middle Aged , Multiple Organ Failure/mortality , Nonlinear Dynamics , Prognosis , ROC Curve , Survival AnalysisSubject(s)
Cholecystitis/microbiology , Enterobacteriaceae Infections/diagnosis , Enterobacteriaceae , Acute Disease , Aged , Female , HumansABSTRACT
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