Bacteria misagglutination in legionella surveillance programmes.

Several respiratory tract illnesses are known to be caused by bacteria belonging to the Legionella genus. As a consequence, monitoring programmes assess the presence of the bacteria and the effectiveness of decontamination. Species assignment is typically performed by rapid agglutination. tests which usually provide unambiguous results in the discrimination and serogrouping of Legionella pneumophila versus Legionella spp., including L. longbeachae, L. bozemanii, L. dumofii, L. jordanis, L. micdadei and L. anisa. We report some cases where these phenotypic procedures failed. Over the course of surveillance programmes, some inadequately identified bacteria from different Italian regions were isolated. They showed morphological and cultural features of Legionellaceae, but agglutination tests for species classification gave negative or ambiguous results. These bacteria were unequivocally identified by DNA sequencing.