Does better identification of the Legionella pneumophila serogroup 1 strains by Sequence-Based Typing (SBT) allow for the implementation of more effective contamination control strategies and more targeted intervention measures?

The purpose of this study was to investigate the distribution of Legionella pneumophila sg 1 sequence types within the water supplies of 56 healthcare facilities (HCFs) in the Piemonte region. Using Sequence-Based Typing (SBT) we typed 22 environmental strains of L. pneumophila sg 1 obtained during routine testing from 2004 to 2009. Thirty-three percent of the STs obtained from our analysis were unique to the EWGLI database. Of the 22 analysed environmental strains, 11 STs were found in man-made water systems that were associated with human disease. Four STs, which in our study belonged to strains isolated in hospital with reported clinical cases, were already known in the literature. The presence of these STs was confirmed by reports of clinical and nosocomial cases (single cases or clusters), especially for ST 1, ST 23, and ST 42, the most frequently and widely distributed STs worldwide. This is the first report in Italy where environmental strains of L. pneumophila isolated from a large geographical area have been identified using SBT. This study confirms that the circulation of some STs is correlated with the development of cluster epidemics in the community or even isolated cases of nosocomial origin. Better identification of the strains which cause the majority of disease would allow for more targeted intervention measures.