The most common causative organism for external otitis in adults is:
Otitis externa is an inflammatory and infectious process of the external auditory canal. Pseudomonas aeruginosa and Staphylococcus aureus are the most commonly isolated organisms. Less commonly isolated organisms include Proteus species, Staphylococcus epidermidis, diphtheroids, and Escherichia coli.
Streptococcus viridans
Staphylococcus epidermidis
Pseudomonas aeruginosa
E. coli