The normal microbial flora of the outer ear canal in healthy Norwegian individuals.

Abstract

The microbial flora of the outer ear canal was determined for 77 healthy individuals (M = 44, F = 33). No growth of any microbe was found in 5% of males and 15% of females. Coagulase-negative staphylococci, dominated by Staphylococcus epidermidis, were the commonest microbe group found (83% of persons sampled). Staphylococcus aureus was found in 7% males and no females. Diptheroids were cultured from 32% of the samples. The only Gram-negative rod found was Hafnia alvei in 4% of individuals. No Vibrio spp. or anaerobic Gram-negative organisms were found. A variety of yeasts and moulds were seen, significantly (p = 0.02) more often in males. In a separate experiment, Malassezia furfur was found in 4/9 males and 0/10 females sampled. Various sampling techniques (dry swab, second dry swab, moist swab) that were compared showed broadly similar results. The normal flora of the outer ear canal is predominantly Gram-positive and the use of a dry swab seems to be a satisfactory method for sample-taking from this area.