Co-infection ofMalassezia sympodialisWith Bacterial PathobiontsPseudomonas aeruginosaorStaphylococcus aureusLeads to Distinct Sinonasal Inflammatory Responses in a Murine Acute Sinusitis Model

Host-associated bacteria and fungi, comprising the microbiota, are critical to host health. In the airways, the composition and diversity of the mucosal microbiota of patients are associated with airway health status. However, the relationship between airway microbiota and respiratory inflammation is not well-understood. Chronic rhinosinusitis (CRS) is a complex disease that affects up to 14% of the US population. Previous studies have shown decreased microbial diversity in CRS patients and enrichment of eitherStaphylococcus aureusorPseudomonas aeruginosa. Although bacterial community composition is variable across CRS patients,Malasseziais a dominant fungal genus in the upper airways of the majority of healthy and CRS subjects. We hypothesize that distinct bacterial-fungal interactions differentially influence host mucosal immune response. Thus, we investigatedin vitroandin vivointeractions betweenMalassezia sympodialis, P. aeruginosa, andS. aureus. Thein vitrointeractions were evaluated using the modified Kirby-Bauer Assay, Crystal Violet assay for biofilm, and FISH. A pilot murine model of acute sinusitis was used to investigate relationships with the host immune response.S. aureusandP. aeruginosawere intranasally instilled in the presence or absence ofM. sympodialis(n= 66 total mice; 3-5/group). Changes in the microbiota were determined using 16S rRNA gene sequencing and host immune response was measured using quantitative real-time PCR (qRT-PCR).In vitro, only late stage planktonicP. aeruginosaand its biofilms inhibitedM. sympodialis. Co-infection of mice withM. sympodialisandP. aeruginosaorS. aureusdifferently influenced the immune response. In co-infected mice, we demonstrate different expression of fungal sensing (Dectin-1), allergic responses (IL-5, and IL-13) and inflammation (IL-10, and IL-17) in murine sinus depending on the bacterial species that co-infected withM. sympodialis(p< 0.05). The pilot results suggest that species-specific interactions in airway-associated microbiota may be implicated driving immune responses. The understanding of the role of bacterial-fungal interactions in CRS will contribute to development of novel therapies toward manipulation of the airway microbiota.