Ear bacteria, coloured scanning electron micrograph (SEM). The healthy outer ear houses a variety of bacteria. Some of the most common bacteria are Staphylococcus epidermis, Turicellaotitidis, Alloiococousotitis, Pseudomonas aeruginosa, Corynebacterium and Streptococcus saprophyticum. Under normal circumstances, this bacterial flora does not thrive. Microbes that inhabit the middle ear are Streptococci, Haemophilus pneumoniae and Moraxella catarrhalis. These bacteria get to the middle ear by migrating through the nasophraynx and Eustachian tube. The outer ear is not as prone to infection but can become infected with bacteria like Pseudomonas aeruginosa, the main cause of swimmer's ear. Otitis media is an infection of the middle ear, caused mainly by Haemophilus influenza, Streptocococcus pneumonia, or Moraxella catarrhalis. Magnification: x12000 at 10cm wide