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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.

Hypothesis: We designed a study to determine the role of mastoid mucosal biofilm in chronic otitis media (COM). Background: Biofilm formation has been found in several chronic airway infections. COM is associated with chronic, recalcitrant infection of the mastoid mucosa, and surgery often is required. Methods: COM patients were divided into 2 groups: one with chronic suppurative otitis media (CSOM) and one with cholesteatoma presence. All COM patients had mastoid involvement in a preoperative computed tomographic scan. The control group consisted of patients undergoing cochlear implantation, with no previous history of chronic otitis media. Mastoid mucosa samples were harvested during mastoidectomy. The samples were studied with multiplex-polymerase chain reaction and with CSLM using BacLight Live/Dead stain. Routine bacterial culture was performed in selected cases. Results: A total of 29 COM patients underwent mastoidectomy. Mastoid mucosal biofilm formation could be found in 19 (66%) of these patients. In the control group, there were 11 cases of cochlear implantation, and 1 patient (9%) presented mastoid mucosal biofilm. In the cholesteatoma group, there were 17 patients, of which, 14 (82%) presented biofilm, whereas in the CSOM group, 5 (42%) of 12 patients presented biofilm. The correlation between COM and biofilm was statistically significant (Fisher’s exact test, p = 0.003), as was the correlation between cholesteatoma and biofilm, in comparison with the CSOM group (Fisher’s exact test, p = 0.046). Conclusion: Mastoid mucosal biofilm could be seen in patients with COM with or without cholesteatoma. The role of mastoid biofilm in the development of cholesteatoma should be studied further. Key Words: BiofilmVCholesteatomaV Chronic otitis mediaV Chronic suppurative otitis media V ConfocalVConfocal scanning laser microscopyVMastoidV MastoiditisVOtitisVPolymerase chain reaction. Otol Neurotol 33:785Y788, 2012.