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

To investigate the microbial changes of long-term hearing aid use culture independently.

Cross-sectional study.

Fifty long-term hearing aid users and 80 volunteer controls with asymptomatic ears.

External auditory canal (EAC) sampling with DNA-free swabs.

Microbial communities in the samples were investigated with amplicon sequencing of the 16S rRNA gene.

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.

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.