Study of the antagonistic relationship between gene expression biofilm of Aspergillus niger and Staphylococcus aureus that cause otomycosis.

Background and purpose: Various species of microorganisms interact in a variety of ecological niches and can lead to infection. A biofilm of one or more species may form during the infectious process. Otomycosis can be brought on by etiologic agents, such as Staphylococcus aureus and Aspergillus niger. This study aimed to survey the antagonistic relationship between the gene expression biofilms of A. niger and S. aureus in the context of otomycosis-related biofilm formation.

Materials and methods: This study examined single-species biofilms of A. niger and S. aureus, as well as mixed-species biofilms of A. niger-S. aureus, over 24 and 48 h. Expression of A. niger biofilm-related genes (eng1, xynB, exo, eglA, eglB, and eglC) was analyzed using real-time polymerase chain reaction (PCR). Impact of S. aureus on the gene expression of A. niger was evaluated and compared to the gene expression of A. niger alone, which served as the control.

Results: Biofilm formation assays showed that A. niger biofilm formation was significantly inhibited when co-cultured with S. aureus, with optical density values dropping from 0.56 (alone) to 0.15 at 24 h and 0.05 at 48 h. Real-time PCR analysis revealed that the expression of A. niger biofilm-related genes, namely eng1, xynB, exo, eglA, eglB, and eglC, increased significantly in single-species biofilms, reaching 2.5, 3, 1.5, 3.5, 2, and 1.7, respectively, at 24 h and 3.5, 4, 2, 4.2, 3, and 2, respectively at 48 h. However, in co-culture with S. aureus, their gene expression was markedly reduced to 0.8, 0.5, 0.4, 0.9, 0.6, 0.5, respectively, at 24 h and 0.5, 1, 0.2, 0.8, 0.6. , and 0.3, respectively, at 48 h, demonstrating a strong inhibitory effect of S. aureus on A. niger biofilm formation and gene expression.

Conclusion: This study described the antagonistic relationship between S. aureus and A. niger on the gene expression biofilm that causes otomycosis, as well as the antibiosis relationship between the two during in vitro biofilm formation. These findings provide new insights into the complex interactions between these microorganisms during infection and may have implications for understanding and managing otomycosis.