Microbiome of the External Auditory Canal: Changes after Long-Term Hearing Aid Use

Objective To investigate the microbial changes of long-term hearing aid use culture independently. Study design Cross-sectional study. Patients Fifty long-term hearing aid users and 80 volunteer controls with asymptomatic ears. Intervention External auditory canal (EAC) sampling with DNA-free swabs. Main Outcome Measures Microbial communities in the samples were investigated with amplicon sequencing of the 16S rRNA gene. Results The final analysis contained 48 hearing aid users, 59 controls. Twenty-four samples were excluded because of low sequence count, recent use of antimicrobials and/or corticosteroids, recent cold, or missing health status. The groups showed significant differences in bacterial diversity (beta div., p = 0.011), and hearing aid users showed lower species richness than the control group (alpha div., p < 0.01). The most frequent findings in both groups were Staphylococcus auricularis, Alloiococcus otitis, Cutibacterium acnes, Corynebacterium otitidis, and Staphylococcus unclassified sp. Hearing aid users' samples presented more Corynebacterium tuberculostearicum than the control samples. Common EAC pathogens, such as Staphylococcus aureus or Pseudomonas aeruginosa were rare. Conclusion Long-term hearing aid use lowers bacterial diversity and modulates the EAC microbiome. The changes mostly affect commensals. Lowered diversity may predispose individuals to EAC conditions and needs more research.