Phenotypic and Molecular Characterization of Pyomelanin-Producing ST2;ST1816/ST195 Causing the First European Nosocomial Outbreak.

is one of the most successful and feared nosocomial pathogens. is considered a global threat in the healthcare setting, mainly owing to its ability to acquire multidrug resistance phenotypes. The pathogenesis is guided by its environmental persistence, as well as the production of numerous virulence factors. In several bacteria, the production of pigments, such as melanin, has indeed been linked with virulence and pathogenicity. Melanin is a brownish pigment, rarely observed in , that potentially reduces the susceptibility of the bacteria to host defense mechanisms and environmental insults. This study reports the first outbreak in Europe by pyomelanin-producing strains, in a tertiary-care university hospital in Pisa, Italy. Phenotypic and molecular analyses were performed.