A Clonal Lineage of Fusarium oxysporum Circulates in the Tap Water of Different French Hospitals

Abstract

Fusarium oxysporum is typically a soilborne fungus but can also be found in aquatic environments. In hospitals, water distribution systems may be reservoirs for the fungi responsible for nosocomial infections. F. oxysporum was previously detected in the water distribution systems of five French hospitals. Sixty-eight isolates from water representative of all hospital units that were previously sampled and characterized by translation elongation factor 1␣ sequence typing were subjected to microsatellite analysis and full-length ribosomal intergenic spacer (IGS) sequence typing. All but three isolates shared common microsatellite loci and a common two-locus sequence type (ST). This ST has an international geographical distribution in both the water networks of hospitals and among clinical isolates. The ST dominant in water was not detected among 300 isolates of F. oxysporum that originated from surrounding soils. Further characterization of 15 isolates by vegetative compatibility testing allowed us to conclude that a clonal lineage of F. oxysporum circulates in the tap water of the different hospitals. IMPORTANCEWe demonstrated that a clonal lineage of Fusarium oxysporum inhabits the water distribution systems of several French hospitals. This clonal lineage, which appears to be particularly adapted to water networks, represents a potential risk for human infection and raises questions about its worldwide distribution. N osocomial infections caused by members of the genus Fusarium have emerged over the past 2 decades (1, 2). Infections caused by Fusarium isolates may be superficial, such as keratitis and onychomycosis, but Fusarium spp. can also cause life-threatening disseminated infections in immunocompromised patients (3). The Fusarium species most often involved are the morphological species Fusarium solani and Fusarium oxysporum (4, 5). These morphological species are now recognized as species complexes due to their high level of phylogenetic diversity (6, 7).Members of the genus Fusarium have a diverse ecology that is linked to an impressive metabolic diversity together with a high genetic diversity. They are primarily known as saprophytes in the environment and are usually found in all types of soils (8-10), and they are frequently associated with plants as saprophytes, endophytes, or pathogens (9, 11). Fusaria may also be found in aquatic habitats, including natural water environments (12, 13) and drinking water distribution systems (14-17).Water distribution systems in hospitals were identified as potential reservoirs for species of Fusarium, where they are thought to be responsible for nosocomial infections (14, 18). Fusaria in water may be aerosolized into the air when the water passes through taps and showers and then inhaled by immunocompromised patients (14). In two previous studies, we detected F. oxysporum in the water distribution systems of different French hospitals, with high concentrations of up to 10 5 propagules liter Ϫ1 in some units (19,20). Heterogeneous distributions according to...

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