Model of Pulmonary Co-Infection of Aspergillus and Pseudomonas in Immunocompetent Mice

Co-infection with Pseudomonas (Pa) and Aspergillus (Af) commonly occurs in the airways of immune-compromised patients or in cystic fibrosis and frequently results in more severe outcomes than mono-infection. We affixed both pathogens to agar beads, separately (Af beads, Pa beads) or on the same bead (AfPa beads) and infected immunocompetent mice, an in vivo Af-Pa interaction model. Endotracheal administration was superior to intranasal, allowing larger beads to be administered resulting in longer lung residence. The CFU of the Af beads, diameter 150-250 mu m, were detectable for <= 21 days. Af-bead-infected mice cleared the Af infection more than mice infected with AfPa beads, but Af clearance was the same with a combination of beads (Af beads + Pa beads). Pa-infected mice had more Pa clearance in the presence of Af than with Pa beads alone. In vitro studies supported our conclusion that the close proximity of Af and Pa (on AfPa beads) was disadvantageous for Af, whereas a larger distance (Af + Pa beads) was not. We demonstrated that the interaction between Pseudomonas and Aspergillus during co-infection can be studied in immunocompetent mice. The mutual inhibition of Af and Pa in vivo appears to be dependent on their proximity. We review the literature relating to animal models of infection with Af, Pa, or both.