Microbiome of the Healthy External Auditory Canal

Abstract

Objective: To investigate the microbiota of the healthy external auditory canal (EAC) culture-independently and to evaluate the usefulness of the swabbing method in collecting EAC microbiota samples. Study Design: Cohort study. Patients: Fifty healthy asymptomatic working-age volunteers. Intervention: Samples were harvested with DNA-free swabs from the volunteers' EACs. Main Outcome Measures: Amplicon sequencing of the 16S rRNA gene was used to characterize the microbial communities in the samples. Results: The swabbing method is feasible for EAC microbiota sample collection. The analyzed 41 samples came from 27 female and 14 male subjects; 4 samples were excluded due to recent antimicrobial treatment and 5 because of low sequence count or suspected contaminant microbes. The four most frequent amplicon sequence variants in the microbiota data were Staphylococcus auricularis, Propionibacterium acnes, Alloiococcus otitis, and Turicella otitidis. Typically, the dominant amplicon sequence variant in a sample was one of the most frequent bacteria, but there were also subjects where the dominant species was not among the most frequent ones. The genus Alloiococcus was least common in females who reported cleaning their ears. Subjects with a high relative abundance of Alloiococcus typically had a low abundance of Staphylococcus, which may be a sign of the two being competing members of the microbial community. Conclusions: The most common bacteria in the microbiome of the healthy EAC were Staphylococcus auricularis, Propionibacterium acnes, Alloiococcus otitis, and Turicella otitidis. The EAC microbiota seems more diverse and individualized than previously thought. Also, ear cleaning habits seem to alter the EAC microbiome.

Microbiome of Acute Otitis Externa

“…Our microbiome results have several differences from previous reports [ 19 , 31 ]. Microbiome composition is affected by many factors, such as the host genome, age, sex, family history, nutrition, and hormones.…”

“…Sebaceous skin sites are dominated by Propionibacterium and Staphylococcus , whereas Corynebacterium prefers moist sites [ 16 ]. Ear canal skin apocrine (ceruminous) and sebaceous glands have been analyzed [ 18 ], but there are few studies on the microbiome of the human ear canal [ 19 ]. In a culture study, Staphylococcus was the most abundant taxon, followed by Corynebacterium and Streptococcus [ 20 ].…”

Alloiococcus otitidis—Cause of Nonspecific Acute Sinusitis: First Case Report and Review of Literature

“…Since its discovery, it has been highly controversial as to whether A. otitidis is truly a pathogen or merely a commensal of the external auditory canal [6]. This is mainly because the organism could be found in the external auditory canal (EAC) of apparently healthy individuals [14]. In a recent study, Sjovall et al, reported that EAC samples with a high relative abundance of Staphylococcus typically had a low abundance of Alloiococcus and vice versa.…”

Cholesteatoma has an altered microbiota with a higher abundance of Staphylococcus species

“…COM, chronic suppurative otitis media (0.05% and 0.04%, respectively). 6 In contrast, common bacteria in acute otitis media, such as Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae, A. otitidis, and T. otitidis, 28,39 were extremely rare (<0.05%) in samples from both diseases.…”

“…The bacterial cells that colonize the skin and mucosa outnumber human cells, and these complex microbial communities have a large impact on human health and disease 1 . The microbiota of the healthy external auditory canal (EAC) is longitudinally stable 2 and well characterized; the dominant commensals are Staphylococcus auricularis (abundance:28.7%), Alloiococcus otitidis (19.5%), Turicella otitidis (18.3%), and Cutibacterium acnes (15.4%), while pathogenic bacteria, such as Pseudomonas aeruginosa , and Staphylococcus aureus , are extremely rare 3–6 . However, when colonizing bacteria migrate through the retraction pocket or a tympanic perforation, they may form biofilms to survive in this abnormal environment, and alter the microbiota 7,8 .…”