Molecular Epidemiology of Aspergillus fumigatus Isolates Recovered from Water, Air, and Patients Shows Two Clusters of Genetically Distinct Strains

Abstract

There has been an increase in data suggesting that besides air, hospital water is a potential source of transmission of filamentous fungi, and in particular Aspergillus fumigatus. Molecular characterization of environmental and clinical A. fumigatus isolates, collected prospectively during an 18-month period, was performed to establish if waterborne fungi play a role in the pathogenesis of invasive aspergillosis. Isolates recovered from water (n ‫؍‬ 54) and air (n ‫؍‬ 21) at various locations inside and outside the hospital and from 15 patients (n ‫؍‬ 21) with proven, probable, or possible invasive aspergillosis were genotyped by amplified fragment length polymorphism analysis. Based on genomic fingerprints, the environmental A. fumigatus isolates could be grouped into two major clusters primarily containing isolates recovered from either air or water. The genotypic relatedness between clinical and environmental isolates suggests that patients with invasive aspergillosis can be infected by strains originating from water or from air. In addition, 12 clusters with genetically indistinguishable or highly related strains were differentiated, each containing two to three isolates. In two clusters, clinical isolates recovered from patients matched those recovered from water sources, while in another cluster the clinical isolate was indistinguishable from one cultured from air. This observation might open new perspectives in the development of infection control measures to prevent invasive aspergillosis in high-risk patients. The genetic variability found between airborne and waterborne A. fumigatus strains might prove to be a powerful tool in understanding the transmission of invasive aspergillosis and in outbreak control.With the continuing increase in the number of severely immunocompromised patients, hospitals are faced with the growing problem of invasive aspergillosis and other opportunistic fungal infections (17). Since treatment of these infections is difficult and the outcome is often fatal, preventive measures are of major importance in the control of invasive filamentous fungal infections. Nosocomial invasive aspergillosis is thought to be primarily airborne; however, despite the use of appropriate hospital air filtration systems, the incidence of this infection continues to increase. Together with the lack of genetic relatedness between airborne strains and those causing invasive disease (10, 12), it is tempting to speculate about the existence of other routes of transmission.As early as 1985, Aspergillus species and other filamentous fungi were shown to inhabit water distribution systems that deliver water to hospitals in Europe and the United States (13). Recently, there has been an increase in data supporting water as a potential source of filamentous fungi and, in particular, Aspergillus fumigatus (1, 2, 4, 28). However, direct evidence that waterborne A. fumigatus strains are involved in human infection is lacking. To test the hypothesis that a wet route of transmission might exist, we performed molecu...

Toll Receptor-Mediated Regulation of NADPH Oxidase in Human Dendritic Cells

“…Mature CGD DC produced normal, if not increased, levels of cytokines (TNF, IL-10, and IL-12) and chemokines (IL-8/CXCL8 and macrophage-derived chemokine/CCL22) and were fully competent in inducing T cell proliferation. These results are in agreement with recent reports showing an increased production of inflammatory cytokines, such as IL-1, TNF, and KC, and IL-10 in CGD-mice and in whole blood samples from CGD patients challenged with Aspergillus fumigatus (15,54,55). The finding that CGD DC induce a normal proliferation of T lymphocytes was further confirmed by the lack of effect of SOD, a radical scavenger, in MLR assays performed with normal DC.…”

Population structure and diversity of the pathogenic fungus Aspergillus fumigatus isolated from different sources and geographic origins

“…On the other hand, group B showed that the AR isolates cluster with some isolates from FR and MX, leading to a relationship close to AR isolates' paraphyletic behaviour. Many reticulations with one-20 mutational changes are seen in the network of isolates, reflecting again the large variability among them, similar to published data by Warris et al (2003). The current study showed that both clinical and environmental isolates of A. fumigatus display genetic diversity, reinforcing conclusions reached by other investigators (Warris et al 2003).…”

“…Many reticulations with one-20 mutational changes are seen in the network of isolates, reflecting again the large variability among them, similar to published data by Warris et al (2003). The current study showed that both clinical and environmental isolates of A. fumigatus display genetic diversity, reinforcing conclusions reached by other investigators (Warris et al 2003). These facts could have repercussions for the diagnosis and treatment of patients with aspergillosis, since it has become more common to find great variation within this species.…”

“…In this study, the AFLP technique used with eight selective base combinations, was found to be useful for distinguishing among A. fumigatus strains obtained from the environment and patients, as well as for identifying the structures of populations and their relationships with their geographical origin, according to previous published results (Warris et al 2003, Bonin et al 2007, de Valk et al 2007.…”

“…Moreover, it is pertinent to point out that in order to obtain greater knowledge about genetic and structural diversity of A. fumigatus populations it is important to obtain a greater number of environmental samples. Further molecular studies analyzing clinical and environmental Aspergillus isolates will be useful in determining the genetic relationships between isolates responsible for infections occurring in the same institution, in revealing whether this filamentous fungus is able to develop different routes of transmission (air and/or water) as has been proposed (Warris et al 2003) and which reproduction mode is primarily used by Aspergillus.…”