Genotypic diversity of Legionella pneumophila in environmental and clinical strains assessed by Sequence-Based Typing, in association with retrospective clinical surveillance in Northern Italy

Objective. The study aimed to evidence previous cases of legionellosis or proven or suspected pneumonia in seven hospital facilities for the mentally disabled in Northern Italy, where no clinical surveillance had been previously carried out. An additional aim was to highlight the occurrence of strains of Legionella pneumophila of clinical and environmental origin by Sequence-Based Typing (SBT), comparing them to world surveillance. Materials and method. A clinical survey was perfomed from 2003-2012, analyzing 615 medical records for hospital-and community-acquired pneumonia, with particular attention to legionellosis. Clinical (n=4) and environmental (n=25) isolates of Legionella pneumophila, isolated in the same period (2003-2012), were characterized by SBT and the Sequence Types (STs) compared with the European Working Group for Legionella Infections (EWGLI) database. Results. Surveillance revealed that there were seven detected cases of legionellosis; most pneumonia cases could not be confirmed by diagnostic tests because of the disabilities of the patients and their lack of cooperation. The same ST was found in two of the clinical strains and also in a corresponding environment, i.e. ST685 and ST16, and two clinical strains belonging to the same ST (ST1). The other environmental strains were isolated in department with confirmed/suspected clinical cases. Five other STs found in this study were new to the database: ST685 was isolated both from a patient and from water; ST694, ST1181, ST1370 and ST1371 have not been described previously. Conclusions. The study confirmed that the routine collection and analysis of environmental strains may be an important strategy for preventing sporadic and epidemic cases of legionellosis, in association with clinical surveillance.