Assessment of the role of Staphylococcus epidermidis as a cause of otitis media

One hundred thirty children with clinical evidence of otitis media were studied. Cultures were obtained from the external auditory canal (prior and subsequent to cleansing), the middle ear (by needle aspiration), the nasopharynx, and throat. Gram stained smears of purulent material obtained from the middle ear were prepared. Isolates of Staphylcoccus epidermidis from the middle ear of patients with otitis media, S. epidermidis isolates from skin, S. epidermidis isolates from blood, and S. aureus isolates from blood were evaluated with regard to lysostaphin sensitivity, lysozyme production, DNAse production, oxygen consumption, growth rate and sensitivity to antibiotics and compared with each other. In ten patients S. epidermidis grew in pure culture on solid media and in nine of these individuals a gram stained smear showed gram-positive cocci within polymorphonuclear leukocytes. Each of these patients had a febrile illness and a bulging red tympanic membrane. Seven of the ten isolates were resistant to penicillin. With regard to most of the metabolic characteristics measured, isolates of S. epidermidis from the middle ear were similar to both pathogenic and nonpathogenic S. epidermidis recovered from other sources. Staphylococcus epidermidis may be the etiologic agent responsible for purulent otitis media in a small number of patients.