Despite the prevalence of Aspergillus-related disease in immune suppressed lung transplant patients, little is known of the host-pathogen interaction. Because of the mould’s angiotropic nature and because of its capacity to thrive in hypoxic conditions, we hypothesized that the degree of Aspergillus invasion would increase with progressive rejection-mediated ischemia of the allograft. To study this relationship, we utilized a novel orthotopic tracheal transplant model of Aspergillus infection, in which it was possible to assess the effects of tissue hypoxia and ischemia on airway infectivity. Laser Doppler flowmetry and FITC-lectin were used to determine blood perfusion, and a fiber optic microsensor was used to measure airway tissue oxygen tension. Fungal burden and depth of invasion were graded using histopathology. We demonstrated a high efficacy (80%) for producing a localized fungal tracheal infection with the majority of infection occurring at the donor-recipient anastomosis; Aspergillus was more invasive in allogeneic compared to syngeneic groups. During the study period, the overall kinetics of both non-infected and infected allografts was similar, demonstrating a progressive loss of perfusion and oxygenation, which reached a nadir by days 10-12 post-transplantation. The extent of Aspergillus invasion directly correlated with the degree of graft hypoxia and ischemia. Compared to the midtrachea, the donor-recipient anastomotic site exhibited lower perfusion and more invasive disease; a finding consistent with clinical experience. For the first time, we identify ischemia as a putative risk factor for Aspergillus invasion. Therapeutic approaches focused on preserving vascular health may play an important role in limiting Aspergillus infections.

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e Iron acquisition is crucial for the growth of Aspergillus fumigatus. A. fumigatus biofilm formation occurs in vitro and in vivo and is associated with physiological changes. In this study, we assessed the effects of Fe chelators on biofilm formation and development. Deferiprone (DFP), deferasirox (DFS), and deferoxamine (DFM) were tested for MIC against a reference isolate via a broth macrodilution method. The metabolic effects (assessed by XTT [2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt]) on biofilm formation by conidia were studied upon exposure to DFP, DFM, DFP plus FeCl 3 , or FeCl 3 alone. A preformed biofilm was exposed to DFP with or without FeCl 3 . The DFP and DFS MIC 50 against planktonic A. fumigatus was 1,250 M, and XTT gave the same result. DFM showed no planktonic inhibition at concentrations of <2,500 M. By XTT testing, DFM concentrations of <1,250 M had no effect, whereas 2,500 M increased biofilms forming in A. fumigatus or preformed biofilms (P < 0.01). DFP at 156 to 2,500 M inhibited biofilm formation (P < 0.01 to 0.001) in a dose-responsive manner. Biofilm formation with 625 M DFP plus any concentration of FeCl 3 was lower than that in the controls (P < 0.05 to 0.001). FeCl 3 at >625 M reversed the DFP inhibitory effect (P < 0.05 to 0.01), but the reversal was incomplete compared to the controls (P < 0.05 to 0.01). For preformed biofilms, DFP in the range of >625 to 1,250 M was inhibitory compared to the controls (P < 0.01 to 0.001). FeCl 3 at >625 M overcame inhibition by 625 M DFP (P < 0.001). FeCl 3 alone at >156 M stimulated biofilm formation (P < 0.05 to 0.001). Preformed A. fumigatus biofilm increased with 2,500 M FeCl 3 only (P < 0.05). In a strain survey, various susceptibilities of biofilms of A. fumigatus clinical isolates to DFP were noted. In conclusion, iron stimulates biofilm formation and preformed biofilms. Chelators can inhibit or enhance biofilms. Chelation may be a potential therapy for A. fumigatus, but we show here that chelators must be chosen carefully. Individual isolate susceptibility assessments may be needed.A spergillus fumigatus, the ubiquitous saprophytic mold, frequently causes respiratory tract infections, including invasive pulmonary aspergillosis and allergic bronchopulmonary aspergillosis (1). A. fumigatus disease occurs most frequently in immunocompromised individuals, such as bone marrow transplant and other neutropenic patients, solid organ transplant recipients (2), and in those with cystic fibrosis (1, 3), chronic granulomatous disease, or chronic obstructive pulmonary disease (1, 4). Despite therapeutic advances in the development and administration of antifungals, mortality from A. fumigatus infection remains high (5).A. fumigatus has shown, in vivo and in vitro, the ability to form biofilms, or complex aggregates of organisms embedded within a polymer-rich extracellular matrix, which demonstrate increased antimicrobial resistance (32). Thus, there is a need for other therapeutic methods with mechanisms that d...

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