New Technique Developed for Species-Level Identification of Live Gram-Negative Bacteria

A new method has now been developed that specifically detects and identifies live Legionella pneumophila in aqueous samples much more quickly than conventional methods, enabling more effective monitoring to prevent epidemics.

Legionella pneumophila proliferates in systems of standing water between 25–50 °C, such as in fountains, boilers, reservoirs, whirlpool tubs, and intermittently used water pipes. Although drinking the contaminated water poses no risk in itself, inhaling droplets often leads to severe lung infections, with a relatively high fatality rate. Frequent monitoring of water samples is necessary to prevent epidemics, but the traditional culture-based method takes several days.

Prof. Sam Dukan, Prof. Boris Vauzeilles, and their team at the multiple institutes of The National Centre for Scientific Research, France (CNRS) developed the new method that specifically identifies live Legionella pneumophila within 1 day. As a gram-negative bacterium, the Legionella cell wall is made up of a species-specific lipopolysaccharide. For the new test, samples are exposed to an azide(N3)-modified precursor compound that only Legionella pneumophila specifically incorporates into its cell wall saccharide units. The azide groups can then be used to bind various (e.g., fluorescent marker) detection probes to the cell surface for detection and identification of the pathogen.

This new technique, described by Mas Pons J., et al. in the journal Angewandte Chemie (International Edition), January 27, 2014, provides easy, relatively rapid, selective detection of a single species of live bacteria, and is the first reported metabolic lipopolysaccharide labeling using a species-specific saccharide for this purpose.

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