Assessment of intercentre reproducibility and epidemiological concordance of Legionella pneumophila serogroup 1 genotyping by amplified fragment length polymorphism analysis

The aims of this work were to assess (i) the intercentre reproducibility an d epidemiological concordance of amplified fragment length polymorphism ana lysis for epidemiological typing of Legionella pneumophila serogroup 1, and (ii) the suitability of the method for standardisation and implementation by members of the European Working Group on Legionella Infections. Fifty co ded isolates comprising two panels of well-characterised strains, a "reprod ucibility" panel (n=20) and an "epidemiologically related" panel (n=30), we re sent to 13 centres in 12 European countries. Analysis was undertaken in each centre following a previously determined standard protocol. Results we re analysed by the participants, using gel analysis software where availabl e, and submitted to the coordinating centre. The coordinating centre reanal ysed all results visually and selected data-sets with gel analysis software . Data analysis by participants yielded reproducibility (R) values of 0.20- 1.00 and epidemiological concordance (E) values of 0.11-1.00, with 6 to 34 types. Following visual analysis by the coordinating centre, R=0.78-1.00,en d E=0.67-1.00, with 10-20 types. Analysis of three data-sets by the coordin ating centre using gel analysis software yielded R=1.00 and E=1.00, with 12 , 13 or 14 types. This method can be used as a simple, rapid screening tool for epidemiological typing of isolates of Legionella pneumophila serogroup 1. Results demonstrate that the method can be highly reproducible (R=1.00) and epidemiologically concordant (E=1.00), with good discrimination. The e lectropherograms generated are amenable to computer-aided analysis, but str ict adherence to a previously defined laboratory protocol is required. Foll owing designation of representative type strains and patterns, this method will be adopted by the European Working Group on Legionella Infections as t he first internationally standardised typing method for use in the investig ation of travel-associated Legionella infections.