MOLECULAR EPIDEMIOLOGY OF AN OUTBREAK OF LEGIONNAIRES-DISEASE ASSOCIATED WITH A COOLING-TOWER IN GENOVA-SESTRI PONENTE, ITALY

Fatty acid profile analysis, monoclonal antibody (MAb) subtyping, puls ed-field gel electrophoresis (PFGE), arbitrarily primed polymerase cha in reaction (AP-PCR), and ribotyping were used to compare clinical and environmental Legionella pneumophila serogroup 1 isolates from an out break of Legionnaires' disease presumptively associated with cooling t owers. According to the Oxford subtyping scheme, the MAb subtype of pa tients' isolates and of two strains originating from a cooling tower w as Pontiac, whereas the other isolates were subtype Olda, The strains showed no intrinsic strain-to-strain difference in fatty acid profiles , and ribotyping and length polymorphism of the 16S-23S rDNA interveni ng regions failed to reveal any differences between the isolates. Conv ersely, PFGE and AP-PCR appeared to be more discriminately, as the sam e genomic profile was found for the clinical and some environmental st rains, Meteorologic and epidemiological data and the results of molecu lar analysis of the Legionella pneumophila serogroup 1 isolates suppor t the hypothesis that the infection was transmitted from one of the co oling towers to the indoor environment of the same building, to homes in proximity that had open windows, and to the streets, In fact, the o utbreak diminished and later ended after a part in the tower was repla ced, This investigation demonstrates the utility of combined molecular methods (i.e., phenotypic and genomic typing) in comparing epidemiolo gically linked clinical and environmental isolates, Finally, the outbr eak confirms the risk of Legionnaires' disease posed by cooling towers , mainly when atmospheric thermal and humidity inversions occur, This finding emphasizes the need to determine whether the source of infecti on is in the living or working environment ol somewhere else.