Designation of the European Working Group on Legionella Infection (EWGLI) amplified fragment length polymorphism types of Legionella pneumophila serogroup 1 and results of intercentre proficiency testing using a standard protocol

The utility of amplified fragment length polymorphism (AFLP) analysis as a genotyping method for the epidemiological typing of Legionella pneumophila serogroup I has been previously demonstrated. This study (i) reports recommendations for the designation of the European Working Group on Legionella Infections (EWGLI) AFLP types, (ii) describes the EWGLI AFLP types identified for the 130 strains in the EWGLI culture collection, and (iii) reports the results of a newly introduced international programme of proficiency testing. Following preliminary analysis of 20 epidemiologically unrelated isolates, 16 major AFLP types were identified. A coded proficiency panel, comprising 12 additional isolates representing 9 of these 16 AFLP types, was sent to 17 centres in 14 European countries where it was analysed following a previously determined standard protocol. The identity of each coded strain (recorded as AFLP type 001-016 or untypeable) was determined by participants with reference to these 16 AFLP types, either visually or using gel analysis software where available, and reported to the coordinating centre. Nine of the 12 strains, including an epidemiologically related pair and two pairs of unrelated isolates of the same type, were correctly identified to the correct AFLP type by all or all but one of the participants. Seven laboratories correctly identified all 12 isolates, and a further seven laboratories correctly identified 11. Type identification scores ranged from 75% (1 centre), 83% (2 centres), and 92% (7 centres) to 100% (7 centres). The AFLP method as described is robust and rapid and allows the genotypic comparison of isolates of Legionella pneumophila between different testing centres without the need for exchange of the strains studied.