Rapid Detection of Legionella pneumophila in Drinking Water, Based on Filter Immunoassay and Chronoamperometric Measurement

Abstract

<i>Legionella</i> is a pathogenic bacterium, ubiquitous in freshwater environments and able to colonise man-made water systems from which it can be transmitted to humans during outbreaks. The prevention of such outbreaks requires a fast, low cost, automated and often portable detection system. In this work, we present a combination of sample concentration, immunoassay detection, and measurement by chronoamperometry. A nitrocellulose microfiltration membrane is used as support for both the water sample concentration and the <i>Legionella</i> immunodetection. The horseradish peroxidase enzymatic label of the antibodies permits using the redox substrate 3,3',5,5'-Tetramethylbenzidine to generate current changes proportional to the bacterial concentration present in drinking water. Carbon screen-printed electrodes are employed in the chronoamperometric measurements. Our system reduces the detection time: from the 10 days required by the conventional culture-based methods, to 2-3 h, which could be crucial to avoid outbreaks. Additionally, the system shows a linear response (R² value of 0.99), being able to detect a range of <i>Legionella</i> concentrations between 10¹ and 10⁴ cfu·mL^-1 with a detection limit (LoD) of 4 cfu·mL^-1.